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Life Returns: Frequently Asked Questions about Plant and Animal Recovery Following the 1980 Eruption


The following written information and photo captions are available for use as direct quotes for media stories, guidebooks, textbooks, etc. Please use this material in the educational context for which it is intended. Quotes can be attributed to Peter Frenzen, Monument Scientist. For use of photographs please see Use Conditions.

Thank you,

Peter Frenzen
Monument Scientist
USDA Forest Service
Mount St. Helens National Volcanic Monument


Vegetation

  • How were the forests at Mount St. Helens influenced by the May 18, 1980 eruption?
  • What is status of plant recovery at the volcano 25 years after the eruption?
  • How is plant recovery likely to proceed in the future?
  • What was the most surprising discovery immediately following the eruption?
  • Were there any plants that survived the eruption?
  • What is the long-term outlook for vegetation recovery in the Monument?

Wildlife

  • What major wildlife species have returned?
  • What is the long-term outlook for wildlife?
  • How were birds affected by the eruption?
  • How were small mammals affected by the eruption?
  • How were insects affected by the eruption?
  • Who were the first colonists in the blast zone and what is their significance?

Streams, Lakes, Amphibians, Fish

  • How were streams affected by the eruption?
  • How were amphibians (frogs, toads, etc.) and reptiles (snakes and lizards) affected?
  • How were lakes affected by the eruption?
  • Are there fish in Spirit Lake?
  • How did the fish get to Spirit Lake?
  • What is the future of fishing and other recreation at Spirit Lake?

Microbial Activity

  • What have scientists learned from their studies of microbial activity in steam fumaroles and thermal springs around the volcano?

Recovery

  • What efforts were successful in aiding the recovery process?
  • Were any trees replanted after the eruption?
  • Were there any recovery efforts that were not a complete success?

Erosion

  • Why was erosion important to the recovery of vegetation on the Monument?

Science

  • What is the role of science in the National Volcanic Monument?
  • What is the position of Monument Scientist?
  • What is the status of research in Mount St. Helens?

Vegetation

How were the forests at Mount St. Helens influenced by the May 18, 1980 eruption?
 

The 1980 eruptions of Mount St. Helens blew down or scorched 230 square miles (500 square km) of forest. The catastrophic failure of the volcano's summit and topographic channeling of the lateral blast produced a complex gradient of disturbance that ranged from complete scouring and burial by high temperature material in the Spirit Lake basin to a dusting of volcanic ash that fell on forests northeast of the blast zone.

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The distribution of forest vegetation around Mount St. Helens prior to the 1980 eruption is visible in this false color composite image from the Landsat MSS satellite.  The western boundary of the Gifford Pinchot National Forest is easily defined by the large clearcuts on private lands northwest of the volcano.

 

 

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The massive size of the 230 square mile blast zone as seen from space is revealed in this 1980 false color composite image from the Landsat MSS satellite.  (Landsat, MSS Composite, 1980)

 

 

For purposes of description the gradient is simplified into five distinct disturbance zones. The following is a brief description of each zone starting with the most heavily disturbed surfaces closest to the volcano and then working outward toward the margins of the blast zone where disturbance was less and more organisms survived.

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 Map of the five distinct disturbance zones formed by the May 18, 1980 eruption. (USDA Forest Service, T. Valentine)

 

  • 1. Pyroclastic Flows  -- On the afternoon of May 18,1980, long after the lateral blast and debris avalanche had run their course, fiery flows of super-heated pumice and gas flowed from the crater and into the valley immediately north of the crater.   Due to extreme temperatures (1300 degrees F, 700 o C) no organisms or organic material survived on the pyroclastic flow deposits.  

 

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Before the 1980 eruption the Spirit Lake basin was cloaked in old-growth forest. The signboard marks a vegetation plot, one of only a few places where the Forest Service had recorded the composition of pre-eruption vegetation at an individual species level. (USDA Forest Service, 1979)

 

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All traces of the pre-eruption forest were erased, first scoured and buried by the debris avalanche and then sterilized by fiery pyroclastic flows that surged from the crater later that afternoon.   The signboard marks same the same location as pre-eruption photo.   The post-eruption plot had to be re-located using surveying instruments.  (USDA Forest Service, 1980).

 

  • 2. Debris Avalanche -- A heterogeneous deposit composed of large mounds and depressions produced when the north side of the mountain collapsed and slid away in the largest landslide in recorded history (0.6 cubic miles, 2.5 cubic km of material).   In less than 10 minutes, the debris avalanche of rock and sediments filled a 20 square mile area (60 km 2 ) of the North Fork Toutle River valley to an average depth of 150 feet (45 m).   Plant survival on these deposits was limited to a few individual plants that sprouted from root fragments that, by chance, ended up on the surface of the deposit.  

 

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Massive chunks of the volcano, called hummocks, were transported down the North Fork Toutle River valley at estimated speed greater than 60 mph (27 m/sec).   The hummocks are the small, steep hills that appear in the photograph.   The massive debris avalanche deposit created a natural dam holding back the waters of Coldwater Lake until an outlet channel was constructed. (USGS, 1984)  

  • 3. Lahars (mudflows) -- Cement-like slurries of glacial melt-water, boulders, and sand-sized sediments fed by melting ice and snow swept down streams around the volcano.   The largest lahars (mudflows) occurred as water trapped within the debris avalanche deposit coalesced and flowed down the valley of the North Fork Toutle River.   The massive Toutle River lahar flowed at velocities up to 27 mph (12 m/sec) and deposited more than 45 million cubic yards (35 million cubic meters) of sediment in the Columbia River channel blocking ocean-going shipping for 13 days until emergency dredging was completed.  Within two minutes of the start of the eruption, hot fragmented rock and gases boiled over the south crater rim melting almost 30 feet (9 m) of snow and ice from the Shoestring Glacier.  The resulting flood of melt water produced lahars that flowed into the Muddy River and Pine Creek to the south and east of the volcano.   Survival was limited to a few individual plants that sprouted from roots swept along the surface of the deposit.   The overall rate of plant recovery on mudflows has been comparatively rapid due to their inherently narrow width and the tremendous influx of seed from adjacent, undisturbed forest that surrounds the mudflow deposits.  

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South side of Mount St. Helens and Shoestring Glacier prior to the 1980 eruption. (USGS, D. Miller)

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 Muddy River lahar deposit following the eruption (USDA Forest Service, F. Valenzuela, 1981

 

Click for larger imageLahars scoured and buried more than 100 miles (160 km) of river channel on the west and southeast sides of the volcano.   The maximum height of the flow is evidenced by mud marks on trees 26 feet (8 m) above the Muddy River.   The two people and helicopter visible in the photo provide a sense of scale. (J. Franklin, USDA Forest Service, 1980)

 

  • 4. Lateral Blast (Downed Tree) Area -- Within a 15 mile (25 km) radius north of the volcano the sideways-directed blast completely fragmented, blew down, or scorched and killed the forest.  The speed of the cloud of fragmented rock and hot gases ranged from 220 to 670 miles per hour (360-1080 km/hour).   Plant survival within the blast area varied from little to none on nearby hillsides to areas with considerable survival in sheltered locations and on the outer margins of the blast zone.  

The lateral blast area is divided into three distinct zones based upon their relative proximity to the blast and the degree of impact:

Tree Removal Zone -- The impact of the blast was greatest on hillsides directly facing the volcano within a 5-mile (8 km) radius north of the volcano.  Entire old-growth trees were pulled apart by the 650-mile per hour blast (300 m/sec) and their splintered remains, in turn, became part of the blast.  

 

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Before the eruption the ridges north of the volcano were shrouded in old-growth Pacific silver fir and mountain hemlock forests.   The forest in this photo is growing on the site of the now popular Windy Ridge viewpoint, four miles (6 km) northeast of the volcano.   The signboard marks a vegetation plot, one of only a few places where the composition of pre-eruption vegetation was recorded at an individual species level. (M. Hemstrom, USDA Forest Service, 1979)

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A repeat photo of the same location shows the scouring effects of the 300 mph, stone-filled blast that not only toppled the trees but also ripped them from the ground (blast direction is from left to right).   The blast stripped the branches from the trees and deposited a jumbled pile of logs on the far side of the ridge.   (USDA Forest Service, 1980)

 Downed Tree Zone -- The lateral blast felled trees up to 12 miles (18 km) in a 180-degree arc north of the volcano. The rock and ash-filled blast was channeled by steep mountain topography. Steep mountain ridges and rock outcroppings deflected the force of the sideways-directed blast leaving sheltered pockets on north-facing slopes. Late-lying snow banks sheltered patches of small shrubs and trees from blast heat and scouring.   

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 The blast flowed around and was deflected by steep ridges.  Blast direction in this photo was from left to right.  Note the standing dead trees that were sheltered behind the steep ridge. (P. Frenzen, 1980)

Standing Dead Tree Zone -- A narrow zone of standing dead trees that was scorched and killed by hot blast gases marks the outer margin of the 1980 blast area.  The comparatively narrow width of this zone results from the physics of the blast and its behavior as it slowed.  Shortly after the blast had slowed to a point where it was no longer felling trees, it reached a point where it could no longer carry the load of fragmented rock and ash that it was carrying.  The blast gases ramped upward like a hot air balloon relieved of its ballast.  This produced a sharp boundary between scorched and adjacent green trees.   

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A band of standing dead trees marked the outer boundary of the 1980 blast zone. The singed needles bear testimony to the 660 deg F (350 deg C) temperature of hot blast gases.  (P. Frenzen, 1980]

 

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The singed needles bear witness to the 660 deg F (350 deg C) temperature of hot blast gases.  (P. Frenzen, 1980)

  • 5. Ashfall Area -- The 15-mile high ash cloud drifted to the northeast depositing more than three feet (100 cm) of ash near the volcano and traces of ash hundreds of miles (km) to the northeast.   The ash cloud eventually encircled the globe.  

The vertical eruption plume continued for more than nine hours on May 18, 1980. (USGS, A. Post, 1980)

 

 

 

The ashfall coated trees growing northeast of the mountain retarding their growth for the first year following the eruption.   After rain cleared the ash from the trees, their growth recovered and, in many cases, actually increased because the ash acted like mulch, retarding the growth of competing understory vegetation.

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Ash-covered noble fir trees in a young plantation on the Gifford Pichot National Forest northeast of the volcano.(USDA Forest Service, J. Hughes, 1980)

However, what was good for some trees was very detrimental to others. The ash caused changes in foliar geometry that resulted in elevated needle temperatures and the death of foliage especially among old-growth Pacific Silver fir trees northeast of the volcano. 

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 Ash-covered noble-fir foliage and needle damage northeast of the volcano. (USDA Forest Service, J. Hughes, 1980)

 

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Prior to the eruption mountain ridges northeast of the volcano supported old-growth Pacific silver fir and mountain hemlock forests. The person is standing at the center of a vegetation plot, one of only a few places where the composition of pre-eruption vegetation had been recorded at a individual  species level.  (USDA Forest Service, 1979)

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A repeat photo of the same point, taken after the eruption, shows the effects of a blanket of volcanic ash that fell from a volcanic ash plume that drifted to the northeast on the prevailing winds.   This is an area located downwind of the volcano and outside of the blast zone.  (USDA Forest Service, 1980)

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What is status of plant recovery at the volcano 25 years after the eruption?

The first 25 years of vegetation recovery at Mount St. Helens can be viewed as the opening chapter in a long-term (200 to 500 year) successional sequence that, in the absence of another large-scale eruption or other disturbance, will eventually return the 1980 blast zone to an old-growth forest.   During the first five years after the eruption, vegetation recovery was dominated by surviving plants that were rooted in pre-eruption soil and managed to sprout through the overlying deposits of volcanic ash and pumice.  

 

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Pearly everlasting sprouts from a small erosion gully following the 1980 eruption.  (USDA Forest Service, J. Franklin, 1980)

 On steep slopes, vegetation re-establishment was helped by erosion that cut gullies in the overlying blast and airfall deposits exposing roots in the pre-eruption soil.  Surviving plants that were able to expand vegetatively (spread by above or below ground runners) greatly accelerated the return of vegetation.   Early established plants helped pave the way for colonizing seeds by providing shade and by adding life-sustaining mulch to the harsh, open blast zone.  Colonizing species, that established from seeds blown in by the wind, soon joined the plant survivors. 

Since 1995, there has been a steady progression in the number and overall variety of plants in the blast zone. This is the result of a progressive "in-filling" process as populations of surviving plants have expanded and colonizing plants have continued to seed-in between the established plants. Over the last 10 years, the most conspicuous change has been an increase in the abundance of trees and shrubs. The overall appearance of the landscape surrounding the volcano has changed as trees such as red alder (Alnus rubra) and shrubs such as Sitka alder (Alnus sinuata) and willow (Salix spp.) have established throughout the blast zone.   This process is most evident on the debris avalanche and lahar (mudflow) deposits, particularly in wet areas formed by ground water seeps and on pond margins. Throughout the blast zone, seedling to sapling-sized conifers (evergreen trees) are also becoming common.  Over the last 25 years, these developing shrub and tree species have spread laying the groundwork for the eventual transformation of the gray blast zone into a thriving coniferous forest once again. 

Vegetation re-establishment has proceeded somewhat differently on each of the five primary eruption disturbance zones. In general, the speed of vegetation reestablishment has varied as a function of the magnitude of initial disturbance, suitability of the deposits for plant establishment and growth, and proximity to seed sources from the undisturbed forest outside the blast zone. A broad generalization of the status of the 25-year vegetation recovery is presented for each disturbance zone below (these zones are the same as those listed on the preceding map):

Pyroclastic Flow Deposits -- Plant establishment on surfaces sterilized by 1500 degree F pyroclastic flows has been comparatively slower than other areas in the 1980 eruption area.   This is due to the virtual absence of organic material on the pumice deposits in the valley immediately north of the crater and the comparatively greater distance of the Pumice Plain to seed sources from intact vegetation outside of the blast zone.  

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Fresh pyroclastic flow deposits directly north of the crater.

(USGS, 1980)

Twenty-five years later the Pumice Plain north of the crater is covered in wildflowers.

(USDA Forest Service,

P. Frenzen, 2004)

Prairie lupine (Lupinus lepidus) has been an important early colonizing plant on the pyroclastic flow deposits because of its ability to fix nitrogen.   Over time, the dense mats of prairie lupines and other plants are adding organic matter and nitrogen to the pumice deposits and are helping to pave the way for other plants to follow.  

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Prairie lupines (Lupinus lepidus) have been an important early colonizing plant on the Pumice Plain (pyroclastic flow deposits) north of the crater.

[James Cook, University of Wisconsin-Stevens Point, 1999]

 

As hardy, high-elevation plants like prairie lupine and other plants have established, there has been more forage available for large herbivores. As elk and other animals spend more time grazing on the Pumice Plain they deposit the seeds of grasses and other plants in their droppings.   Over the last decade, the abundance of grasses is increasing as a result of the presence of large grazing animals.  

 

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View looking across the Pumice Plain towards the volcano. The clumps of grass visible in this picture has established from seed transported to the site by elk and deposited in their droppings. 

(James Cook, Univ. of Wisconsin-Stevens Point, 1999) 

Debris Avalanche Deposit - Plant establishment on the debris avalanche deposit has been strongly influenced by substrate stability, availability of water, and proximity to vegetation on adjacent hillsides that escaped scouring and burial by the debris avalanche. Over the last 25 years, vegetation development on floodplains adjacent to the North Fork Toutle River has been minimal. Even though many seeds may sprout each year in the moist sediments along the river, few seedlings survive the erosion and deposition of sediments by the continually shifting channel system.

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The barren, gray appearance of the floodplain of the North Fork Toutle River reflects a lack of vegetation development due to periodic disturbance from seasonal flooding.

(P. Frenzen, USDA Forest Service, 1988) 

Groundwater seeps were among the first places that seedlings established on the debris avalanche deposit.

(P. Frenzen, USDA Forest Service 1983)

 

High winds transport the seeds of trees and other plants great distances across the comparatively smooth, open debris avalanche and lahar (mudflow) deposits in the North Fork Toutle River valley. Seeds of all of the common conifers (evergreen tree species) have blown onto the debris avalanche deposit.  In some cases it appears that these seeds have blown in from intact forests up to five miles away.  

 

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Lodgepole pine (Pinus contorta) is an example of a successful evergreen tree species that has established on the debris avalanche deposit.  Lodgepole is a tree that is well adapted for rapid establishment and growth on the nutrient poor volcanic deposits. Its capacity to produce numerous seeds at a comparatively young age will ensure its abundance in the future forest.

(P. Frenzen, USDA Forest Service, 1999)

Red alder (Alnus rubra) is an example of a fast growing hardwood tree that has flourished on the debris avalanche deposit. Alder has an association with bacteria on its roots that enables it to fix nitrogen. The availability of nitrogen, an essential nutrient, allows red alder to grow at a rate of two to three feet per year (1 m) on the debris avalanche deposit.  The growth rate of red alder far exceeds the 2 to 3 inch per year height growth (5-8 cm) of the common conifers (evergreen trees) Douglas fir and western hemlock.

 

Red alder is a fast growing deciduous tree that has been an important early colonizer on the debris avalanche near Coldwater Lake. As alder has matured and produced seed it has spread rapidly across the barren deposits and is working its way across the North Fork Toutle valley.  

(P. Frenzen, USDA Forest Service, 1999)

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The most well developed red alder stands are found along the margins of the debris avalanche deposit where they established first due to the relative proximity of adjacent seed sources. Within the next decade much of the debris avalanche deposit will be covered in a dense thicket of red alder. 

(P. Frenzen, USDA Forest Service, 1999)

 

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A steady increase in the number of red alder and Sitka alder (Alnus sinuata) seedlings found in the center of the valley provides testimony to the continuing spread of these fast growing species across the debris avalanche deposit.  

(P. Frenzen, USDA Forest Service, 1999)

 

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Debris avalanche deposit near Coldwater Lake.  Note the soft appeaance of the deposit surface due to fine material on the surface.

(USDA Forest Service, F. Valenzuela, 1981)

The influence of erosion is evident in the same view rephotographed two years later.

(USDA Forest Service, F. Valenzuela, 1981)

Colonization of the debris avalanche deposit by red alder is evident in the same view rephotographed 24 years after the 1980 eruption.

(USDA Forest Service,

P. Frenzen, 2004)

 

 Lahar (mudflow) deposits - With the exception of floodplains that are subject to frequent disturbance, plant establishment has been relatively rapid on lahar deposits. The cement-like lahars scoured and buried streamside vegetation along streams for great distances beyond the blast zone boundary. Lahars produce comparatively narrow, ribbon-like deposits because they are channeled by and confined to stream bottoms. Except for floodplains that are chronically disturbed, the narrow deposits are quick to revegetate because of the tremendous amount of seed received from the adjacent, undisturbed forest that lines the edges of lahar deposits that are located outside of the volcanic blast zone.

 

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The Muddy River lahar deposit as seen from the Lahar Viewpoint on the south side of the volcano, one year after the eruption.  Note the undisturbed forest that lines the sides of the 1980 lahar deposit.  The Muddy River is located on the south side of the volcano and was not affected by the north-directed lateral blast.  The yellow car parked on the road provides some sense of scale for this enormous lahar deposit.

(F. Valenzuela, USDA Forest Service, 1981)

 

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The same view 18 years later shows that forest reestablishment on lahar deposit is well underway.  (P. Frenzen, USDA Forest Service, 1999)

 

 

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The establishment of trees near the margins of the Muddy River lahar deposit has been rapid. This reflects the heavy rain of seeds from the adjacent, undisturbed forest.  (P. Frenzen, USDA Forest Service, 1999)

 

Lateral Blast (Downed Tree) Zone - The speed of vegetation reestablishment was generally related to the degree of intensity of a given location from the lateral blast. The most intense scouring and thickest blast deposits were on ridges directly facing the blast within a five-mile radius north of the volcano.  Geologists called this area, where trees were pulled apart by the force of the blast or ripped from the ground and blown off the hillsides, the tree removal zone. 

The impacts of the lateral blast in the tree removal zone is revealed by a time sequence of photos of vegetation recovery at Windy Ridge viewpoint shows the eruption impacts and the recovery of vegetation over time.

 

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Before the eruption, the ridges north of the volcano were shrouded in old-growth Pacific silver fir and mountain hemlock forest. The forest in this photo is growing on the site of the now popular Windy Ridge viewpoint, four miles (6 km) northeast of the volcano. The signboard marks a vegetation plot, one of only a few places where the composition of pre-eruption vegetation was recorded at an individual species level.  (M. Hemstrom, USDA Forest Service, 1979)

 

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A repeat photo of the same location shows the scouring effects of the 300-plus mph, stone-filled blast that not only toppled the trees but also ripped them from the ground (blast direction is from left to right). The blast stripped the branches from the trees and deposited a jumbled pile of logs on the far side of the ridge.  (USDA Forest Service, 1980)

 

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This repeat photograph of the Windy Ridge viewpoint shows the result of 19 years of plant establishment on the blast-scoured hillside. Note that vegetation in the foreground is still concentrated in gullies where buried soil and roots were exposed by erosion. 

(P. Frenzen, USDA Forest Service, 1999)

 

Plant community development in the blowndown forest has been most rapid on north-facing slopes that faced away from the blast and areas where sapling-sized trees and shrubs were protected by late-lying snow banks. The comparatively rapid growth of snow-protected trees and shrubs can been seen through a sequence of photographs taken from the same point.

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Blowndown forest on a north-facing slope near Meta Lake. Snow protected Pacific silver fir and mountain hemlock trees are growing rapidly in the open blast zone three years after the eruption.

Re-sprouting shrubs are also visible.  

(P. Frenzen, USDA Forest Service, 1983)

 

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Same view of blown down forest near Meta Lake, nine years after the eruption. Note the growth of the surviving trees and that numerous snow-protected shrubs have also resprouted.

(P. Frenzen, USDA Forest Service, 1989)

 

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Same view of blown down forest near Meta Lake, 14 years after the eruption.  Note the comparative large size and continued growth of the snow-protected trees and shrubs. 

(P. Frenzen, USDA Forest Service, 1994)

 

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Surviving trees and shrubs sheltered by snow and wetlands plants that resprouted from pre-eruption soil lined the shoreline of Meta Lake, four years after the eruption.  (F. Valenzuela, USDA Forest Service, 1984)

 

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This repeat photo of the Meta Lake shoreline, seven years after the eruption, shows the slow but steady growth and expansion of surviving plant species.

(P. Frenzen, USDA Forest Service, 1987)

  

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The same view, 19 years after the eruption, shows the reestablishment of wetland plants along the shoreline of Meta Lake.

(P. Frenzen, USDA Forest Service, 1999)

In areas of blowndown forest that were snow-free at the time of the eruption, plant development has also been rapid. "Weedy" plant species, like fireweed and pearly everlasting, have established from their abundant, wind-dispersed seed. In the last several years, it is increasingly evident that establishment of the future forest is well underway. The seedlings of red alder, willow and Douglas fir trees can now be found growing among the shattered remains of the previous forest.

 

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Plant establishment in areas that were not snow covered at the time of the eruption can be seen in this view of blown forest near Independence Pass. Willows, alders and Douglas fir trees have established from seeds blown in from several miles away.

(P. Frenzen, USDA Forest Service, 1999)

 

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The importance of erosion to plant survival and recovery can still be seen 19 years after the eruption on this site where the forest had been clearcut prior to the 1980 eruption. Note that most of the plant life is still distributed along the erosion gullies that were carved in the otherwise flat and, therefore, intact ash deposits.   (P. Frenzen, USDA Forest Service, 1999)

 

Standing Dead Tree (Singe) Zone

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The influence of snow on plant survival and patterns of vegetation recovery can still be seen in the standing dead forest along the 99-road northeast of the volcano, 20 years after the eruption. Note the patches of green where late lying snow provided shelter to small trees and shrubs. 

(P. Frenzen, USDA Forest Service, 1999)

 

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The growth of the next forest rising beneath the remains of the previous forest can be seen along the 99-road corridor. These snow-protected Pacific silver fir and mountain hemlock trees are among the largest naturally established evergreen trees within the core of the 230 square mile blast zone.  (P. Frenzen, USDA Forest Service, 1999)

 

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Standing dead forest three years after the eruption.

(USDA Forest Service, 1983)

Fifteen years after the eruption, light-seeded "weedy" plant species have established.  Note the number of fallen trees.

(USDA Forest Service, P. Frenzen, 1995)

Few trees remain standing 24 years after the eruption.  Establishment of the next forest is well underway.

(USDA Forest Service, P. Frenzen, 1995)

 

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How is plant recovery likely to proceed in the future?

How is plant recovery likely to proceed in the future?

Over the last decade, the blast zone north of the volcano has gradually been transformed from gray to green.  This apparent "greening" of the landscape has resulted from the progressive "pixel by pixel" colonization of the formerly gray, open space between established plants. As more and more trees and shrubs establish, evidence of the 1980 eruption will disappear beneath a layer of developing vegetation. Within a few decades, scattered coniferous trees such as Douglas fir (Pseudotsuga menziesii), Western hemlock (Tsuga heterophylla), lodgepole pine (Pinus contorta) and Pacific silver fir (Abies amabilis) will begin to emerge from beneath the hardwood and shrub thicket. By 2100, these scattered emerging trees will begin to converge and the area will take on the appearance of a young forest. By the year 2200, barring another large-scale eruption or other disturbance, much of the area will once again be covered in an old-growth forest as it was before the 1980 eruption.  This repeats a cycle of volcanic destruction and renewal that has been underway during the 40,000 year eruptive history of the volcano. 

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Debris avalanche deposit viewed from Johnston Ridge following the eruption.

(USGS, 1980)

The progressive greening of the landscape is evident in the same view 24 years after the eruption.

(USDA Forest Service,

P. Frenzen, 1980)

 

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 What was the most surprising discovery immediately following the eruption?

The single greatest surprise to scientists entering the blast zone shortly after the eruption was the realization that many organisms survived in, what initially appeared to be, a lifeless landscape. Scientists entering the blast zone for the first time found a mostly gray and brown landscape covered with dead trees and a uniform covering of ash and pumice.

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Pre-eruption view from the former summit of Mount St. Helens looking north with Spirit Lake and Mount Rainier in the background. Note the dark green color of the old-growth forests that occupied the valley to the north of the volcano and the ridges surrounding Spirit Lake.  (Peter Frenzen, 1978)

 

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The same view after the eruption shows the extensive removal of forest vegetation north of the volcano. The missing trees were buried by the massive landslide (debris avalanche) or ripped from the ground and/or toppled by the lateral blast.
( J. Franklin, USDA Forest Service, 1980)

 

It wasn't long before scientists working in the area found surviving populations of plants and animals. This was particularly evident in areas protected by snow cover and where erosion had thinned the overlying ash deposits (along streams and in gullies that formed on hillslopes). Plants were observed sprouting from the pre-eruption soil surface and signs of activity by gophers and ants indicated that subterranean animals (living below ground) had survived beneath the volcanic ash. 

The survival of plants and animals in the midst of the apparent total devastation was of special interest to the scientific community. Early studies have demonstrated that, even after a large-scale, catastrophic disturbance, recovery processes are strongly influenced by carry over of living and dead organic material from pre-disturbance ecosystems. At Mount St. Helens, ecosystem recovery was influenced not only by the survival of plants and animals, but also by the tremendous quantities of organic material that remained in the standing dead and blown down forest.  

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Were there any plants that survived the eruption? 

The early spring timing of the eruption meant that there were still late-lying snow banks on high mountain ridges that sheltered some forest plants from the full effects of the blast.

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Post-eruption view of a blast-sheltered, north-facing ridge that was snow-covered and facing away from the blast at the time of the eruption (blast was moving from right to left). Note the standing dead trees that were snapped off at the point where they were taller than the ridgetop. Trees that survived the eruption under snow can also be seen on the sheltered side of the ridge.  (P. Frenzen, USDA Forest Service, 1985)

 

The most conspicuous plant survivors were isolated patches of sapling-sized Pacific silver fir (Abies amabilis) and mountain hemlock (Tsuga mertensiana) trees that survived the eruption intact, bent over beneath deep snow banks. Other woody plants like huckleberry (Vaccinium spp.) and salmonberry (Rubus spectabilis) bushes managed to survive on snow-covered north slopes or in isolated pockets on the backside of steep mountain ridges that deflected the full force of the blast.

 

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Snow-protected Pacific silver fir and mountain hemlock trees provided the first early glimpses of green in a mostly gray and brown landscape. Over time as these survivors grow they will serve as important sources of seed for the establishment of the future forest inside the blast zone at Mount St. Helens.  (Art McKee, Oregon State University, 1980) 

Timing of the eruption was also important to the survival of non-woody plants at the volcano. The eruption hit the plants at a time when they were least vulnerable to scouring by the blast and burial by volcanic deposits. Late May is a time when plants on mountain ridges were still dormant having dropped their leaves and died back to buried roots the previous fall. The most common means of plant survival was from rootstocks that sprouted from the surface of the pre-eruption soil where ash deposits were thin (less than six inches, 15 cm) or where the pre-eruption soil surface had been exposed in the bottom of erosion gullies. 

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The impact of the lateral blast on shoreline vegetation can readily be seen along the shoreline at Panhandle Lake, one year after the eruption. Plant life during the first few growing seasons was limited to sapling-sized trees that were sheltered by snow and plants that sprouted from surviving roots that were excavated by erosion. 

(F. Valenzuela, USDA Forest Service, 1981)

 

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The expansion of surviving plant life and recolonization of buried soil exposed by erosion can be seen in a repeat photograph of the shoreline at Panhandle Lake, three years after the eruption. 

(F. Valenzuela, USDA Forest Service, 1983)

 

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This repeat photograph from 1987 shows the continued growth of surviving trees and shrubs at Panhandle Lake. 

(F. Valenzuela, USDA Forest Service, 1987)

Other chance circumstances contributed to plant survival throughout the 230 square mile blast zone. In the blown down forest, scattered plants managed to survive on blocks of soil that clung to the root masses of upturned trees. Other plants survived in sheltered pockets underneath the blowndown trees. These lucky survivors included forest plants species such as bunchberry dogwood (Cornus canadensis), queens cup beadlily (Clintonia uniflora) as well as common shrub species such as huckleberry (Vaccinium spp.) and elderberry (Sambucus spp.).

 

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Huckleberries (Vaccinium spp.) and other forest understory plants resprouted from soil on the root masses of blown down trees providing an early glimpse of green in a mostly gray landscape
(J. Franklin, USDA Forest Service, 1982)

 

The most common survivors were "weedy plant" species such as fireweed (Epilobium angustifolium) and pearly everlasting (Anaphalis margaritacea) that sprouted from the original soil surface in areas that had been clearcut prior to the eruption.

 

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The surviving roots of weedy plants, like fireweed, sprouted where they could reach the ash surface, either through surface cracks or in gullies where buried soil was exposed by erosion.  (J. Franklin, USDA Forest Service, 1980)

 

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At first glance this ash-covered clearcut, located 9 miles northeast of the volcano, appeared completely lifeless following the eruption.
(Art McKee, Oregon State Univ., 1980)

 

Click for larger imageThe same view taken five years later reveals the weedy plant survivors that sprouted from rootstocks that were present in the pre-eruption soil beneath the ash. Weedy plant species such as fireweed (Epilobium angustifolium), pearly everlasting (Anaphalis margaritacea) and Canada thistle (Cirsium arvense) possess vigorous root systems and are well adapted to rapid growth in harsh, open conditions.
(P. Frenzen, USDA Forest Service, 1986) 

In years following the eruption, plants adapted to life in the cool, dark forest understory succumbed to the comparatively harsh blast zone environment. Seedlings of "weedy" plants such as fireweed and pearly everlasting that are better adapted to life in the open, post-eruption environment gradually replaced the forest plants. Weedy plants are favored in the blast zone because of their dispersal capabilities and tolerance of environmental extremes.

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Plant life slowly returned to the blown down forest and, because individual plants were few and far between, the landscape still looked mostly gray three years after the eruption. Countless seeds drifted into the blast zone but only a few took root on the sun-baked ash surface.  (USDA Forest Service, 1983)

 

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Six years after the eruption colonizing plants had begun to fill the available open space and wildflowers framed the blown down forest. Over time these early colonizing plants have added organic matter and nutrients to the ash surface helping to modify harsh environmental conditions and pave the way for other plant life to follow.  (P. Frenzen, USDA Forest Service, 1986)

 

The "weedy" plant species that survived in areas that had been clearcut prior to the eruption and in young plantations north and west of the volcano provide a tremendous seed source for colonization of the blast zone. Fall visitors to the Monument encounter millions of cotton-covered seeds drifting on the wind. At times the drifting seeds of "weedy" plant species are so numerous that it almost appears to be snowing. As the drifting seeds take hold, the 1980 blast zone is gradually being transformed from gray to green.  These early colonizing plants are the first step towards the reestablishment of the old-growth forests that once framed Spirit Lake and Mount St. Helens. 

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What is the long-term outlook for vegetation recovery in the Monument?

In the years ahead, we expect that "weedy" plants such as fireweed and pearly everlasting will continue to dominate the 1980 blast zone.  These early colonizers are being joined by willows and other shrubs. Fast growing hardwoods such as red alder (Alnus rubra), black cottonwood (Populus trichocarpa) and bitter cherry (Prunus emarginata) are spreading across the open blast zone.  The future forest is taking root with the establishment of coniferous trees including Douglas fir (Pseudotsuga menziesii), Pacific silver fir, noble fir (Abies procera), western hemlock (Tsuga heterophylla), mountain hemlock and lodgepole pine (Pinus contorta) . Within the next 50 years, as the young trees mature, the weed and shrub dominated landscape will begin to take on the appearance of a young coniferous forest. Within 100 years a mature forest will cover most of the area. Within 200 years the area will begin to resemble the old-growth forests that framed the vvolcano prior to the 1980 eruption.

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The slow but steady return of forest vegetation can be seen in this aerial view of the debris avalanche deposit near Castle Lake five years after the eruption. Note the green color of wet areas and pond shorelines where the seeds of sedges, willows and other wetland plants have taken root.
(P. Frenzen, USDA Forest Service, 1985)

 

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Nineteen years after the eruption the forests return to the debris avalanche is well underway. One of the most successful trees has been red alder (Alnus rubra), a tree that disperses easily and is capable of rapid growth on the nutrient-poor, volcanic deposits.  (P. Frenzen, USDA Forest Service, 1999) 

It is difficult to precisely predict the future structure and composition of plant life at Mount St. Helens due to the uncertainty associated with the prevailing weather (incidence of recurring drought and/or flooding) or future volcanic activity. What is certain, however, is that the landscape and biota surrounding Mount St. Helens will remain in a state of continual change. The cycle of volcanic activity followed by biotic response at Mount St. Helens has been underway for more than 40,000 years. It is likely that the cycle will be repeated many times in the future.

 

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Between 1980 and 1986 there were a number of small steam and ash eruptions as a series of dome building eruptions built the 1000-foot tall lava dome in the crater. This is a view of a dome shattering explosive eruption that occurred in the fall of 1982.  (Peter Frenzen, 1982 

 

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Wildlife

What major wildlife species have returnedWhat major wildlife species have returned?

The most conspicuous wildlife species that have returned to the blast zone are Roosevelt elk (Cervus elaphus) and the Columbia black-tailed deer (Odocoileus hemionus). Large mammals did not survive but animals from adjacent, less-disturbed areas were able to move into the blast zone soon after the eruption. These animals found prime habitat due to the availability of high quality summer forage from surviving plants and winter forage from grass and clover planted to control erosion on the debris avalanche deposit west of the Monument. The availability of winter forage contributed greatly to the recovery of the elk population.

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It is not unusual to see large herds of bull elk running together on the debris avalanche or in the blast zone north of the volcano. Elk viewing is a very popular activity among Monument visitors. 

(C. Tonn, USDA Forest Service)

 

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What is the long-term outlook for wildlife?

Given an area with ample food supply and little human disturbance (public access and hunting has been restricted in the valley immediately north of the volcano since the eruption) elk herds have expanded dramatically and have become a visible part of the Monument. Elk viewing is a popular activity among Monument visitors. The Washington State Department of Wildlife estimates that elk populations have returned to near pre-eruption levels (1,750 animals in the area surrounding Mount St. Helens). In the years ahead it is expected that elk and deer will continue to be abundant. In the absence of human intervention (e.g. hunting in the core of the blast zone) it is likely that populations will continue to increase dramatically until there is a string of hard winters and a dieback occurs due to a shortage of winter forage. 

The winter of 1998/1999 provided an example of the kind of population fluctuations that can occur as forest plantations on adjacent private lands mature and the forage supply decreases in the Mount St. Helens area. The winter of 98 buried the available forage for elk and deer beneath a record snow pack (more than three times normal). More than 200 elk starved to death in the snow-covered blast zone as winter snow blocked their access to forage in a late spring. The record snow pack of 98 had placed an additional stress on a population that had already begun to run up against the limits of the available food supply during the winter season. The reduction in forage was due in part to the growth of forest plantations on private lands adjacent to the Monument. As the branches of adjacent plantation trees have grown together the availability of sunlight for the growth of forage between the plantation trees has been greatly reduced. What turned out to be a very stressful winter for elk at the volcano turned into a boon for scavengers and predators. Animals like coyote, bear and even wolverines were sighted in places in the blast zone where they had never been seen before. 

In order to examine the relationship between large-herbivores and developing vegetation the Monument has installed several experimental plots called exclosures where elk and deer are excluded through the use of an 8-foot tall stock fence. In each case 1.25 acre (0.5 hectare) area is fenced and the composition and abundance of developing vegetation is periodically measured both within the fence and on an adjacent, unfenced "control" plot. The exclosures will provide a means of assessing how large herbivores are influencing vegetation composition both in terms of what they eat and terms of the seeds that they deposit in their droppings.

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The influence of elk on plant establishment and growth can be seen in the relatively low abundance of fireweed blooms visible in an unfenced "control" plot that has been repeatedly browsed by elk and deer. The control plot is located adjacent to the fenced area where elk and deer have been experimentally excluded since 1991 (for comparison see fenced plot in next photo). (P. Frenzen, USDA Forest Service, 1994)

 

Click for larger imageThe increased bloom of fireweed in response to exclusion of elk and deer can be seen inside this experimental fenced area. This 1.25 acre (0.5 hectare) exclosure is one of three sets of adjacent fenced and unfenced experimental plots established by biologists to monitor the influence of large herbivores on plant succession.
(P. Frenzen, USDA Forest Service, 1994)

 

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The biggest difference between vegetation inside versus outside a fenced elk and deer exclosure on the debris avalanche is the difference in the growth form of the trees. Trees outside of the fence have a shrubby appearance due to repeated browsing while trees inside of the fence exhibit the upright growth form that is typical for trees.  

         (P. Frenzen, USDA Forest Service, 1999)

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How were birds affected by the eruption?

 

Bird survival was restricted to areas on the margins of the blast zone where ashfall was the only disturbance. Recolonization of the blast zone occurred very quickly (hours, days, weeks) due to the tremendous dispersing capability of birds. Geologists working in the steaming crater experienced the tremendous dispersal capability of birds first hand as they were dive bombed by hummingbirds attracted to their bright orange flight suits (the birds thought they had stumbled upon the largest flowers they had ever seen!). 

Ten years after the eruptions, few species are present in the pyroclastic flow, debris avalanche and tree blowdown zones where vegetation recovery has been relatively slow. The common raven (Corvus corax), mountain bluebird (Sialia currucoides) and white-crowned sparrow (Zonotrichia leucophrys) are examples of species that have returned to the most heavily disturbed areas. The standing dead forests harbor species such as the American robin (Turdus migratorius), hairy woodpecker (Picoides villosus) and red-breasted nuthatch (Sitta canadensis) but lack many of the foliage loving species found in undisturbed forests. Ashfall areas support bird life similar to adjacent, undisturbed forested sites. In time as the blast zone returns to a forested condition we should observe a return of bird life found in adjacent, undisturbed forests.

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Birds like the mountain bluebird (Sialia currucoides) that nest in cavities in standing dead trees have prospered in the blast zone
(J. Quiring, USDA Forest Service)

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How were small mammals affected by the eruption?

 

Of the 32 species of small mammals thought to be living near Mount St. Helens only 14 were known to have survived. The eruption adversely affected small mammals either directly through immediate injury or death or indirectly by reducing the availability of food, water or hiding cover. Small mammals that live beneath the soil surface such as the northern pocket gopher (Thomomys talpoides) or hibernators such as the Pacific jumping mouse (Zappus trinotatus) survived where other surface dwelling or non-hibernating animals perished. Species that have returned to the blast zone tend to be generalists having few specific habitat requirements and a broad food base (deer mouse, Peromyscus maniculatus and golden-mantled ground squirrel, Spermophilus saturatus). Species with narrower requirements will probably not return until forest vegetation recovers and food and hiding cover are abundant.

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The northern pocket gopher (Thomomys talpoides) is an example of a ground-dwelling species that survived the eruption in the shelter of its underground burrow.  (Charlie Crisafulli, 1985)

 

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How were insects affected by the eruption?

 

The heat and scouring of the blast combined with deposition of volcanic ash was lethal to insects both in the blast zone and ashfall areas. Volcanic ash affects insects in much the same way as the powder based insect sprays used by homeowners to kill them. The sharp ash particles wear away at the thick cuticle that protects insects from desiccation. Mortality from lack of moisture is probably the greatest single limiter to insect survival. Ash particles also kill insects by clogging the small body pores through which they breathe. There was a noticeable lack of insects in the blast zone during the first few years after the eruption. The exception was ant colonies that survived in logs or below ground and resumed their activities soon after the eruption. 

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Who were the first colonists in the blast zone and what is their significance?

 

The first resident invertebrates observed in the blast zone, apart from ant colonies that survived below ground, were ballooning spiders and beetles. Ballooning spiders spin a parachute-like web that enables them to disperse long distances. These animals are scavenging predators that feed upon other insects that are blown into the area. On a summer day the upper air column is filled with flying insects that are swept aloft and carried great distances. Scientists estimate that 80 pounds (36 kg) of insects are deposited on each acre of the Monument during the four summer months that insects are active. Arthropod fallout, as it is termed, is not only an important source of food for scavenging arthropods but it provides an important source of carbon and other nutrients for future soil development on the volcanic deposits. Wind blown insects are actually helping to pave the way for the development of future forests at Mount St. Helens.

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Spiders and other scavengers like this carabid beetle were among the first residents on the pumice plain north of the volcano. These scavengers survived by feeding on the carcasses of other insects that had been blown into the blast zone by prevailing winds.

(Bob Parmenter, Univ. of New Mexico, 1987) 

Entomologist, Rick Sugg reports that only two of the 12 species of ants that were thought to occupy the pre-eruption landscape managed to survive the eruption. Ground dwelling beetles such as the carabid managed to survive by feeding on below ground fungi.

Click for larger image More and more insects are colonizing the blast zone as developing plant life provides a source of food and shelter. Grasshoppers forage among the lupines on the pumice plain. Such insects provide a food source for small mammals and insectivorous birds. As food and shelter become increasingly available animals are colonizing the blast zone in ever increasing numbers.

(J. Gale, USDA Forest Service, 1994)

 

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How were streams affected by the eruption?

 

Streams were affected differently depending on proximity to the volcano and the degree of impact received. Streams were affected by the tremendous influx of nutrients leached from the blast deposits and by the large quantities of sediment introduced by erosion. Large masses of sediment were washed into streams filling streambeds and causing rapid channel changes and chronically unstable streambeds. The rate of recovery of streams varied with the quantity of sediment introduced, steepness of streambed and presence of large, stable logs in the stream channel. Where large, stable logs were left the streambed was anchored producing a series of pools and riffles that aided the recovery of fish habitat (spawning gravels and substrates for aquatic insects upon which the fish feed). In the absence of large, woody debris fish habitat has been slow to recover. Fish that survived under ice-covered lakes have served as sources for the recolonization of blast zone streams. Anadromous (migrating) fish appear to survive their journey up the sediment-laden waters of the Toutle River to spawn in clear waters of tributary streams.

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Following the eruption blast zone streams like Clearwater Creek nine miles northeast of the volcano were filled with ash and logs.
(J. Franklin, USDA Forest Service, 1980)

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Large quanitities of volcanic ash was washed into streams from blast zone hillslopes.

(USDA Forest Service, J. Hughes, 1980)

 

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Streams, Lakes, Amphibians, Fish

How were amphibians (frogs, toads, etc.) and reptiles (snakes and lizards) affected?

Many amphibians were inactive at the time of the eruption burrowed in lake or stream bottoms or beneath logs and rocks. Survival was generally greater among the aquatic than terrestrial forms due to the tremendous sheltering capacity of water and moist sediments. Recolonization of newly formed habitats was particularly rapid for highly mobile amphibians (frogs and toads) that can travel considerable distances during cool, wet weather. 

Research Ecologist Charlie Crisafulli of the US Forest Service, Pacific Northwest Research Station estimates that there are 5,000 western toads living in the Mount St. Helens area. This is particularly impressive given that populations of western toads are declining in other locations in western North America. Crisafulli attributes their relative success to a temporary lapse in populations of their natural predators following the eruption and an abundance of algae, a key food source in open blast pools and lakes. 

Following the eruption reptile survival was limited to adjacent undisturbed areas or areas receiving ashfall only. During the early years following the eruption garter snakes (Thamnophis spp.) and Northern alligator lizards (Elgaria coerulea) were observed only in ashfall areas outside of the blast zone. This is consistent with the presumed restricted occurrence and limited abundance of reptiles in the area prior to the 1980 eruptions. As plant and insect life has returned garter snakes have been observed throughout the blast zone.

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The tremendous reproductive capacity of amphibians is evidenced by the large number of recently emerged western toads (Bufo borius) on the shoreline of Meta Lake in the blown down forest northeast of the volcano.  (Todd Cullings, 1989) 

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How were lakes affected by the eruption?

Prior to the eruption Spirit Lake and other lakes were typical cold, clear mountain lakes (low nutrients, productivity and temperature with high clarity). The removal and virtual vaporization of forest vegetation by the blast caused great changes in the physical and chemical structure of lakes within the blast zone. Tremendous quantities of useable ammonium, carbon and other energy sources (sulfur, iron and manganese) were leached into the lakes as rainwater percolated through the shattered forest and ash deposits.

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Prior to the eruption high mountain lakes like Obscurity Lake, 10 miles north of Mount St. Helens, were characteristically clear due to extremely low levels of dissolved nutrients.  (USDA Forest Service, 1978)

 

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The same view after the eruption shows the extent of eruption damage to the forest surrounding Obscurity Lake. Note the large quantity of volcanic ash that was eroded from adjacent hillsides and deposited on large deltas at the mouth of inlet streams.  (USDA Forest Service, 1980)

 

Lakes such as Spirit, Coldwater and Castle Lakes that were closer to the volcano were much more heavily impacted. The levels of organic and inorganic nutrients that leached into the lakes were much higher where deposits were thicker and blast intensities (shredding and scorching of forest vegetation) were greater. The water in Spirit Lake was completely displaced by the avalanche and heated to body temperature (a 200 foot (60 m) wave washed against the ridges to the north). 

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A pre-eruption view of Mount St. Helens from Spirit Lake shows the smooth, conical slopes of a very young, and potentially explosive volcano.
(J. Hughes, USDA Forest Service)

 

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The same view shows the profound change in the volcano and Spirit Lake. The formerly clear mountain lake had been completely displaced by the massive landslide and choked with ash and organic debris.
(J. Franklin, USDA Forest Service, 1980) 

Coldwater and Castle Lakes are two examples of lakes that were created as rainwater was impounded inside drainages by the debris avalanche deposit. Meta Lake is an example of a high elevation lake where fish survived the eruption first under ice cover and then in a lens of fresh water that persisted on the surface following the spring thaw. Ryan Lake is one of many lakes not covered with ice where fish perished as microbial activity tied up the available oxygen in the excessively nutrient rich waters that developed in the months following the eruption.

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Following the eruption Ryan Lake, 12 miles north of the volcano, was filled with organic material ranging in size from large logs to dissolved organics. As fall rains washed in nutrients from the blast-shattered forest Ryan Lake was transformed into an organic rich stew teeming with microbial activity. 

(S. Greene, USDA Forest Service, 1980 

Widespread oxygen depletion occurred as bacterial populations responded to increased nutrient levels. Within the first year after the eruption the biological system was transformed from oxygen based system to one dominated by anaerobic heterotrophs (methanogens that obtain their energy from either hydrogen or acetate).

Anoxic conditions persisted for a relatively short period of time. Within five years after the eruption the lakes had mostly returned to normal as wind and seasonal turnover stirred oxygen into the water column and available nutrients were depleted as dead microbes and fine sediments settled to the bottom of the lakes 

Click for larger imageWater samples reveal the tremendous quantity of dissolved organics that leached into blast zone lakes following the eruption. The dark-colored beaker at left is from a nutrient-rich, hot spring that flowed from volcanic deposits. The center beaker is from Coldwater Lake soon after the eruption while the right beaker is from the lake one year later. The difference in clarity between the center and right beakers shows how quickly the water cleared as nutrients were processed by microbial activity and diluted by incoming rain and snow melt.  (Cliff Dahm, Univ. of New Mexico, 1981)  

 

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Are there fish in Spirit Lake?

Yes. In 1993, the Washington Dept. of Fisheries and Wildlife (WDFW) found the first salmonid fish, a rainbow trout, in Spirit Lake. It was 8 inches long and weighed 0.25 pounds. Genetic analysis was performed to attempt to determine the origin (source population) for this fish. Genetic testing indicated that the fish did not appear to be related to modern hatchery strains. However, given the limited sampling data and low resolution of testing, it is impossible to pinpoint the origin of post-eruption fish in Spirit Lake. 

A second fish was located in Spirit Lake in 1994. This fish was 18 inches long and weighed 2.75 pounds. Genetic analyses are being completed on this second fish and the results will be compared to those done on the specimen found in 1993. 

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Since 1980, biologists have periodically surveyed blast zone lakes to determine how fish populations responded to the 1980 eruption. Biologists set gill nets or fish by hook and line for pre-determined intervals to develop estimates of population levels and size distribution of fish in Monument lakes.
(J. Nieland, USDA Forest Service, 1981)


 

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How did the fish get to Spirit Lake?

It is clear that fish could not have survived in the lake following the debris avalanche and the several months when supply of oxygen in the lake was depleted by microbial activity (for more information see lakes explanation above). How fish returned to Spirit Lake remains a mystery. It is likely that fish were illegally stocked by an angler. Colonization would only have been possible after the biological recovery of Spirit Lake following the eruption (influx of fresh water, processing of excess nutrients by bacteria and return of oxygen to its surface waters). The total number of fish in the lake is unknown at this time. Further studies are being planned to assess both of these questions. 

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What is the future of fishing and other recreation at Spirit Lake?

The Monument's Fish and Wildlife Plan guides the management of fish and wildlife by the Forest Service and the Washington Dept. of Fisheries and Wildlife within the 110,000-acre National Volcanic Monument. Even though the Monument Act specifically allows opportunities for recreational fishing, it was determined that representative lakes within the blast zone (including Spirit Lake) would be set aside for scientific research and would not be stocked with fish. "These recommendations recognize the value of managing for a recreational fishery on some lakes, while allowing others to remain undisturbed so that natural recovery processes may continue unimpeded with the option for research studies (Page 41, Monument Fish and Wildlife Plan, 1989)." 

The Washington State Wildlife Commission has closed Spirit Lake to fishing consistent with the Monuments Fish and Wildlife Plan. The Commission recognizes the importance of Spirit Lake and its surroundings as a unique natural laboratory for research and for the enjoyment of future generations. This will allow future Monument visitors to witness the natural recovery process unimpeded by human activity.

The Spirit Lake basin and valley of North Fork of the Toutle River west to Monument boundary (Class I Research Area) is closed to public access, except on developed trails. At this time, the only trail access to Spirit Lake is to the northeastern shore of the lake via the Harmony Falls Trail located off Forest Road 99. Spirit Lake is listed as closed for fishing in the Washington Department of Fish and Wildlife regulation pamphlet. Monument policy clearly indicates that access to the Spirit Lake basin (and rest of the Class I Research Area) will be on developed trails only. This will help protect opportunities for long-term research and allow our future visitors to have the opportunity to observe natures own recovery processes at work in Spirit Lake.

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A biologist displays a cutthroat trout at a high mountain lake north of Mount St. Helens. This is one of a number of lakes in the volcanic blast zone that are readily accessible by road or trail and are available for recreational fishing.
(S. Lanigan, USDA Forest Service, 1991) 

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What have scientists learned from their studies of microbial activity in steam fumaroles and thermal springs around the volcano?

Click for larger imageThe 900-foot tall lava dome that formed in the crater between 1980 and 1986 still retains a considerable amount of heat today. Erosion from flooding and seasonal run-off has cut deep gullies in the crater floor. Where the groundwater beneath the dome is exposed hot, mineral rich thermal springs occur. These thermal areas provide a special habitat for bacteria and other microbial life.  (Tim Lichen, 1990) 

The high nutrient, low oxygen conditions that existed at extreme temperatures following the eruption and still persist in steam fumaroles and thermal springs draining the deposits were similar to the conditions that existed during the early stages of the evolution of life on earth. Microbiologists have repeatedly sampled steam fumaroles and thermal springs to study primitive bacteria (Archaebacter spp.) that occur only in volcanic areas and in very high temperature vents deep on the ocean floor.

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Arrows point to a cross-sectional view of archaebacter as seen through a powerful electron microscope. Archaen bacteria are only found in high temperature, high pressure thermal springs and are thought to have been among the earliest life forms on earth.
(Cliff Dahm, Univ. of New Mexico, 1981)

Mount St. Helens is a particularly good place to study evolutionary processes because microbiologists have been able to study these populations from inception and track their evolution along temperature and chemical gradients that occur at increasing distances from thermal sources. These gradients may approximate the same changing conditions (cooling, oxygenation and dilution of nutrient concentrations) that existed in the wake of widespread volcanism millions of years ago. Scientists working at Mount St. Helens are able to study microbial responses simultaneously along gradients that approximate changes that occurred over very long time scales during the early stages of the development of life on earth.

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Primitive bacteria like archaebacter can be found in the high-temperature, nutrient-rich thermal springs in the crater. Mats of thermophilic algae and filamentous bacteria can also be found growing in the warm streams that flow from the crater floor. Scientists who sample these systems must contend with a variety of hazards ranging from potentially pathogenic bacteria to near constant rock fall from the unstable gullies and crater walls.  (Tim Lichen, 1990)


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Recovery

What efforts were successful in aiding the recovery processes?  

The first thing to point out in answering this question is that there is a very important difference between areas within the boundaries of the legislated National Volcanic Monument and adjacent lands designated for commodity production. Within the legislated Monument 110,000 acres are managed by the USDA Forest Service for research, recreation and most importantly to ensure that natural processes and features continue to develop substantially unimpeded by human activity. To examine successes and/or failures in aiding recovery process, one has to look outside of the legislated National Volcanic Monument in the managed landscape.

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In 1982 Congress established the 110,000-acre Mount St. Helens National Volcanic Monument on the Gifford Pinchot National Forest (red at center is volcanic crater and Monument boundary is outlined in blue). The Monument is dedicated to the protection of the unique natural features created by the 1980 eruption for the benefit of future generations.  (USDA Forest Service, 1982)  

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Were any trees replanted after the eruption? 

Probably the biggest single factor aiding forest recovery on managed lands has been tree planting. The Forest Service salvaged 200 million board feet of blown down and standing dead timber from 10,000 acres. To date nearly 10 million trees have been planted to reforest more than 14,000 acres of National Forest land. The survival of planted trees has been very good because forest managers used the best planting techniques and planting stock available. Survival of planted trees has generally exceeded 70 percent. Trees planted 10 miles northeast of the volcano in the Clearwater valley are growing well and many plantations are ready for pre-commercial thinning.

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The Clearwater Valley is a portion of the volcanic blast zone that is located outside the Congressionally set-aside Monument, in an area designated for multiple-use management. This 1981 photograph shows what the area looked like after the eruption.  (USDA Forest Service, 1981)

 

Click for larger imageWith the exception of designated research plots, wildlife trees and streamside protection zones the blown down and standing dead trees in the Clearwater Valley were removed as part of a massive timber salvage and recovery operation. The green color in this 1987 photograph is from the more than four million trees that the Forest Service replanted in the Clearwater Valley following the eruption. Today the trees in these plantations have been pre-commercially thinned and many trees are over 20 feet tall.  (USDA Forest Service, 1987) 

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Were there any recovery efforts that were not a complete success?

As far as judging the success of recovery efforts, its difficult to say that something was a mistake, because hindsight provides clarity of vision that didn't exist at the time of the emergency response. At the time aerial seeding was approved no one knew that the roots of surviving native plants were waiting to re-sprout from the apparently lifeless ash deposits. If managers were faced with the same situation today, probably the single biggest difference would be that less resources and effort would be dedicated to erosion control seeding. Today, erosion control seeding is generally applied on a much more restricted basis and whenever possible native plant species are used. 

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Erosion 

Why was erosion important to the recovery of vegetation on the Monument?

Erosion played a very important positive role in the recovery of native plants at Mount St. Helens and, ultimately, the long-term stabilization of blast zone hillslopes. From the standpoint of ecosystem recovery at St. Helens, erosion should be viewed as a positive process. The erosion that occurred during the first winter broke up the overlying ash and enabled many native plants to re-sprout and survive. In many areas where thick ash deposits prevented re-sprouting plant recovery was restricted to erosion gullies on steep slopes. These early plant survivors provided a good seedbed (shade and litter) and thus paved the way for the recovery of plant life in the blast zone.

The positive influence of erosion on vegetation recovery is a key lesson learned for managers of Cascade Volcanoes. Where eruptions bury existing vegetation and ash deposits are comparatively thin (less than 10 inches) it is very likely that the surviving native vegetation will be the most dominant force in stabilizing the hillslopes. In these cases it is unlikely that introduction of non-native grass species will be a cost effective means of revegetation.

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Erosion gullies formed quickly as runoff from the first fall rains began to cut through the fresh ash deposits.
(F. Swanson, USDA Forest Service, 1980)

 

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Same view as preceding picture. Following the first winter erosion gullies had cut down through the ash exposing the pre-eruption soil surface. The roots of plants that were lucky enough to have been exposed in gullies were able to re-sprout and survive.   (F. Swanson, USDA Forest Service, 1981)

 

Click for larger imageFour years after the eruption willows and other plants are seen growing from the same erosion gully. In this way, erosion can be viewed as a positive process that helped to contribute to the survival of native plants that have contributed to the revegetation and eventual stabilization of blast zone hillslopes.
(F. Swanson, USDA Forest Service, 1984) 

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Science 

What is the role of science in the National Volcanic Monument?

When Mount St. Helens erupted in 1980, an outstanding scientific opportunity was created, as a result, scientists from across the country and throughout the world came to Mount St. Helens to observe geologic and biological processes first hand. The importance of Mount St. Helens as a national resource for scientific study and public appreciation of volcanic features and processes was recognized and, in 1982, Congress established the Mount St. Helens National Volcanic Monument (NVM) on the Gifford Pinchot National Forest. In the 25 years since the eruption, research has been an important source of basic information for land managers and for visitors who come to learn about the geology and biology of the area.

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The Monument is an important laboratory for both geologic research and long-term studies of how nature responds to infrequent, large-scale disturbances.
(U.S. Geologic Survey, 1980)

 

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The Monument Science program is responsible for promoting the continuation of long-term studies at the volcano. In order to ensure that natural processes and features are protected we periodically assesses the status of vegetation in and around popular trails and visitor facilities. Such baseline monitoring provides an indication of how well the Monument is meeting its fundamental preservation objectives.  (P. Frenzen, USDA Forest Service, 1994) 

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What is the position of Monument Scientist?

The Monument Scientist serves as the primary liaison between the Forest Service and scientists engaged in research at St. Helens. The job of the Monument Scientist and staff is to document research that has been conducted such that baseline research sites and information from long-term studies are documented for the benefit of current and future generations.

Another important task is to disseminate information about baseline studies to the scientific community to promote additional opportunities for research in the Monument. Our objective is to make scientists in the region aware of the tremendous baseline data available, opportunities for continuing existing research and the establishment of new studies.   

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What is the status of research in Mount St. Helens?

The overall level of research at Mount St. Helens is declining as we move away from the period immediately following the May 18, 1980 eruption. As time goes on it appears there are fewer investigators actively engaged in research at the volcano. This is true both in the geologic and the biologic sciences although the U. S. Geological Survey continues to maintain a substantial presence at Mount St. Helens. The USGS is involved in a constant monitoring of the volcano as a means of assessing potential hazards related to volcanic activity and downstream flooding. 

Research in the Biological Sciences tends to be confined to the efforts of a few dedicated investigators who are continuing studies that were established during the first few years following the eruption. In many cases these investigators are continuing their research at St. Helens in a bootleg fashion, in some cases temporarily diverting their efforts from other studies to gather additional data from permanent research installations at the volcano. 

The 2004/2005 eruptive activity and growth of a new lava dome has generated significant renewed interest in research at Mount St. Helens.  Efforts are underway to link opportunities associated with long-term data sets and discoveries made over the past 25 years with the next generation of scientists.  It is truly an exciting time at Mount St. Helens! 

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04/25/00 

 





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