Emerald Robinson: Hi! I am Emerald Robinson and in this What Is video we are going to investigate a very unique formation of ice called a glacier. A glacier is defined as a slowly moving river of ice, but not all masses of ice are glaciers. To qualify to be a glacier ice must be at least 600 of a square mile in size and over 164 feet thick. Earth's largest glacier is eastern Antarctica's Lambert Glacier which is about 60 miles wide over 250 miles and 8000 feet thick.
Glaciers form in places where snow accumulates over a long period of time. As the snow gets deeper the resulting weight and pressure turns the bottom layers of snow into ice. This high pressure combined with the force of gravity causes the glacier to move. Although most glaciers move very slowly, some move as fast as 100 feet per day. Glaciers exist on every continent and play a major role in shaping the face of a earth through erosion. Water from the bottom layer of the glaciers seeps into cracks in the earth where it freezes and expands loosening rocks and boulders from the earth surface. These rocks are dragged along the glacier's path. The earth beneath the glacier becomes smooth as smaller rocks and debris become frozen in the glacier's lower layers, acting like sandpaper. Glaciers carve lakes and valleys or natural dams and create river beds. The water that melts from a glacier surface is the largest source of fresh water on the planet. Although glacier melt also called retreat as a normal part of the water cycle, scientists have noted that glacier are retreating faster and further than ever and point to this as evidence of global warming.