Last week I received an email in which the writer was very concerned about the volcanoes that were appearing in Wisconsin. She asked my what I knew and how much of a danger these volcanoes posed. There hasn’t been an active volcano in Wisconsin for almost 2 billion years. Having one appear in an area that no longer has the underlying geology to support one would indeed be concerning. More about that in a minute, but first the good news. The volcano of which this individual heard about posed no immediate danger to state residents. It was an ice volcano.
Ice volcanoes, also known as snow volcanoes or cryovolcanoes if you have a more scientifically oriented vocabulary, occur with relative frequency on Lake Michigan and in Green Bay, where the most recent sitings were located. They also appear in the other Great Lakes and on other bodies of water which are capable of forming ice.
Ice volcanoes form when ice gathers near the shore of the lake. Water continues to flow under the ice and is pushed up into cracks and crevices in the ice by waves. The pushed up water freezes on the surface of the ice. This results in a cone shape forming around the gap in the ice. When water is pushed through this hole, the cone spews water, just like a volcano would spew molten lava. Ice volcanoes can form and disappear in relatively short periods of time. If conditions are favorable, they can continue to grow taller.
The major danger from an ice volcano would occur to someone climbing on them, as the ice might collapse. Otherwise, they are one of the many interesting weather related phenomena that the Great Lakes give to us.
Volcanoes in Wisconsin
What we normally think of as a volcano is a mountain or hill, typically conical, having a crater or vent through which lava, rock fragments, hot vapor, and gas are being or have been erupted from the earth’s crust. As has been state, Wisconsin has not had an active volcano in almost 2 billion years. At this time, volcanoes were common in the central part of the state.
Since volcanoes were common, Wisconsin has undergone a number of major geologic upheavals. Several hundred million years ago, Wisconsin was covered by a shallow sea. After that, parts of the Wisconsin were covered by glaciers. These events, along with the movement of tectonic plates have left Wisconsin without any volcanoes.
The Closest Active Volcanoes
The closest active volcanoes to Greendale, Wisconsin are Mount Shishaldin, Alaska which is 3,352 miles from here and Kilauea, Hawaii which is 4,271 miles distant. In addition to these areas, the map below shows other volcanically active areas. The closest one to Wisconsin is Yellowstone. Currently, none of these present any danger at all to those of us in Wisconsin.
See the USGS Hazards Program page for an updated version of this map.
Acknowledgements: Wisconsin Department of Natural Resources, United States Geological Survey.