Shelf Ice

Shelf ice can form to look like small mounds along the shore. NEVER step onto shelf ice.

Thad Donovan

Avoid Tragedy: Stay Off Ice

 

Shelf ice lines the shore at West Beach.

Thad Donovan

Fatal Attraction

The shorelines of each Great Lake are distinctive and stunning, but Lake Michigan stands out as the deadliest of the five Great Lakes. The lake is unmistakably dangerous in the winter as frigid temperatures attempt to freeze the shore.

Though shelf ice is gorgeous to observe and may appear solid, shelf ice is inherently unstable. In many places shelf ice cannot support a person’s weight. Sudden shifting and breaking of the ice make it especially hazardous. Never step onto shelf ice.

 

This graphic demonstrates how a hidden hole in shelf ice mounds can lead to the icy waters of the lake beneath, with little chance of climbing out.

Tom Gil

What is Shelf Ice?

Although shelf ice appears solid, it provides only a false sense of security. Shelf ice forms when breaking waves and spray freeze in frigid air temperatures, creating irregularly patterned ice full of cracks, crevices, and holes. Shelf ice is an unstable formation that builds from the beach out to the lake, without freezing to the lake bottom. Due to the nature of its structure and fluctuating temperatures above and below freezing, shelf ice is unpredictable and unsafe to step on.

Shelf ice is not a continuous sheet. Thinned or weakened areas may be hidden, and the ice can collapse like a trapdoor leading to a plunge into icy waters. Entering the water, your body goes into shock, and the nature of the ice makes it difficult to remove yourself. Hypothermia begins in a matter of minutes. Wave action and fragile ice obstructs rescue potential. Death is likely.

 

Snow and ice blur the end of the beach and the beginning of Lake Michigan.

Thad Donovan

Viewing Shelf Ice Safely

Although climbing and stepping onto shelf ice is forbidden, visitors can still experience this Arctic-like enchantment by viewing from a safe distance. Once covered in snow and ice, even frequent lakeshore visitors can have trouble determining where the beach ends and where the lake begins. To be safe, view the shelf ice from the base of the first sand dune or further inland. Only view shelf ice from solid ground, and never attempt to climb it.

 

Fragments of ice are pushed and fused together by Lake Michigan's currents and waves.

Thad Donovan

How Shelf Ice Forms

In winter, Lake Michigan's temperature drops. Ice begins to form on the lake's surface and along its edges. Currents and wave action carry floating ice to the shore at Indiana Dunes National Park, and if temperatures are low enough, the ice begins to crash together, stack up and grow.

This crusty layer thickens, but never freezes to the lake's bottom. Because of this, wave action and currents continue beneath the surface, making the ice unreliable.

 

Lake Michigan's ice sculptures can take many forms.

Thad Donovan

Ice in Motion

Lake Michigan brings continual change to the shores of Indiana Dunes. Currents and waves, as well as inconsistent temperatures mean that the shelf ice's conditions are always shifting.

Waves can crumble shelf ice, breaking off hunks and sweeping them down the coast. Waves can also thicken the shelf ice by adding a thin layer of water onto the ice's surface and freezing it. Large waves can also smash floating pieces of ice onto the shelf. Spray from waves can create dazzling ice sculptures.

As our climate continues to warm on a global scale, ice on Lake Michigan is as ephemeral as ever. Warm temperatures can come in early spring, but are also increasingly showing up throughout winter. Temperatures above freezing weaken and melt the ice. The amount of ice on our shore is trending down in the past few decades. Shelf ice is an important protective barrier for the beaches and dunes. The rigid structure blocks the brunt of the force of Lake Michigan's waves, protecting the shoreline from erosion.

 

Ice mounds or volcanoes can disorient visitors that mistake them for dunes.

Thad Donovan

Mounds and Ice Volcanoes

The forces of Lake Michigan and fluctuating temperature results in ice formations along the lakefront that come in an endless variety of shapes.

If wave action breaks a hole into a layer of shelf ice, the formation of an ice volcano or mound can begin. Waves continue to rhythmically push water through the hole and onto the shelf ice's surface. The water continues to freeze and eventually builds up a mound that can reach upwards of 20 feet above the surface of the lake. These hollow shoots can be hidden and are just another reason why shelf ice can be fatal. Never attempt to climb an ice mound or ice volcano on shelf ice.

 

Additional Resources

For more information on how to safely visit in cold weather, check out these Winter Hiking Tips.

Visit our Winter Activities page for more information on things to do while visiting Indiana Dunes National Park in winter.

Visit our general Safety page for more safety information.

Visit NOAA's Great Lakes Ice Cover page for up-to-date information on Great Lakes Ice Cover.