Winter travel may require crossing frozen or partially frozen lakes, streams or ponds. Traveling over ice requires constant vigilance and decision making. Check ice conditions frequently.
If your adventure includes travel on ice, carry an ax, portable drill or ice pick to test the thickness. If a single blow reaches water, stay off the ice.
- In the cold winter months, four inches of ice is generally safe for ski, dog team. If you are on a snowmachine, you will need five to six inches of ice for safe travel.
- More than a foot of ice is necessary for any kind of travel in the spring, as rotting conditions set in making ice conditions less stable.
- Clear, black ice can be thin or thick. Estimate thickness by the depth of cracks or bubbles in the ice.
- If you hear running water or your footsteps sound hollow, STAY OFF! You are on a thin ice shelf above water.
What causes weak ice?
- Moving water—movement erodes ice. Be cautious wherever water could be moving under the ice—at the junction of two rivers, near outlets and inlets of lakes, and around beaver lodges and the spill point of beaver dams.
- Groundwater seepage—the movement of warm, seeping water near lake edges and springs can weaken ice.
- Decomposition areas—warming and the release of methane bubbles can create open holes or bubbles under thin ice. These conditions are typical in swamps or marshes.
- Wet Overflow—although frozen overflow thickens the ice, it is not as strong as pure frozen water. Ice crystals in overflow are jumbled, pure water crystals are perfectly aligned.
- Spring rotting—patchy snowmelt, moving water, and dark objects on the ice speed up melting. Be careful along bank and shore edges.
- Sea ice—salt in its crystalline structure makes sea ice weaker than fresh water ice. Watch out for open leads, holes, and pressure ridges.
- Warm winds
- Pressure cracks
If you are in doubt about ice thickness or stability, stay off the ice.
(photo by Irene Lindquist)