What's the term that describes snow that doesn't melt, then compresses over many years into ice, and slowly moves across land?
And the answer is: A glacier.
A glacier is a huge mass of ice that moves slowly over land, under its own weight. Sometimes referred to as "rivers of ice," glaciers form where snow accumulates over many years, often over centuries.
Glaciers are so powerful, they quite literally move the earth around. Alpine glaciers, one of two major glacier types, form on mountainsides and can create or deepen valleys by pushing dirt or rocks out of the way. These glaciers are found on every continent except Australia, though there are many in New Zealand.
Ice sheets, unlike alpine glaciers, are not limited to mountainous regions. They form broad domes and spread out from their center to all directions. Often called continental glaciers, this glacial variation covers most of Antartica and some of Greenland.
Have you heard of an ice flow? Learn about the difference between a glacier and an ice flow in this article from Encyclopedia Britannica.
Pulled by gravity and the sheer weight of ice, glaciers move very slowly, usually only a few centimeters a day. Over time, they are able to pick up rocks, dirt, clay and other sediments, sometimes carrying boulders the size of houses. These forces of ice have been the means of creating countless lakes, valleys and mountains around the world. Much of the fertile soil in the Great Plains of North America was formed from layers of till left by ancient ice sheets.
Check out the video below to learn more about glaciers: