Pressure Ridge Spotted on Mississippi River

A law enforcement officer at Frontenac State Park snapped a recent picture of a pressure ridge on the Mississippi River. The Goodhue County Sheriff's Office described it on Facebook as "beautiful yet dangerous."

If you are one to venture out on the ice Monday, be very careful.

How do pressure ridges form?

According to the Minnesota Department of Natural Resources, pressure or "ice ridges" are caused by the pushing action of a lake’s ice sheet against the shore. Cracks form in the ice because of different contraction rates at the top and bottom of the ice sheet. This is especially true in years that the ice sheet lacks an insulating snow cover. Ice cracks also develop because the edges of the ice sheet are sometimes firmly attached to the shore.

When water rises in the cracks and freezes, the ice sheet expands slightly. Rising air temperatures warm the ice, leading to additional expansion, which exerts a tremendous thrust against the shore. Alternate warming and cooling of the ice sheet leads to additional pushing action, causing the ice to creep shoreward and scrape, gouge, and push soil and rock into mounds (called “ice ridges”, “ice pushes”, or “ramparts”).

Image via Goodhue County Sheriff's Office