A glacier is a mass of accumulated snow and ice that originates in a mountain range and takes hundreds to thousands of years to form. The frozen water moves over the land, carving and transforming the landscape. According to the National Snow and Ice Data Center, glacial till is the rock and soil material that has been carried by a glacier as it moves and is left behind when the glacier melts or retreats.
Glacial till is a heterogeneous mixture of everything the glacier has picked up along the way. Geologist Michael Pidwirny of the University of British Columbia Okanagan says that the elements in glacial till can range in size from tiny particles of clay to huge boulders.
Moraines are mounded deposits of glacial till left behind in the landscape. According to Pidwirny, lateral moraines form when material comes from the outer edges of a glacier, while a medial moraine is the deposit left when two glaciers flow together and their lateral moraines are deposited between them. Terminal moraine is the deposit of glacial till that marks the farthest point of the glacier's advance after it retreats.
A till plain forms when a huge sheet of ice detaches from a glacier and melts in place, leaving behind its load of unsorted gravel, mud and rock spread over a wide area. According to the National Snow and Ice Reference Center, glacial till can form the basis for good farmland.