moraine

One could do worse than simply to quote Joseph Le Conte, from A Journal of Ramblings through the High Sierra of California, published in 1875. Le Conte, the first professor of geology at the University of California, was on a hiking and exploring trip in Yosemite with John Muir when he made the following notes: “On the surface, and about the foot of glaciers, are always found immense piles of heterogeneous debris consisting of rock fragments of all sizes, mixed with earth. These are called moraines. On the surface, the most usual form and place is a long heap, often twenty to fifty feet high, along each side, next to the bounding cliffs. These are called lateral moraines. They are ruins of the crumbling cliffs on each side, drawn out into a continuous line by the motion of the glacier. If glaciers are without tributaries, these lateral moraines are all the debris on their surface; but if glaciers have tributaries, then the two interior lateral moraines of the tributaries are carried down the middle of the glacier, as a medial moraine. There is a medial moraine for every tributary. In complicated glaciers, therefore, the whole surface may be nearly covered with debris. All these materials, whether lateral or medial, are borne slowly onward by the motion of the glacier, and finally deposited at its foot, in the form of a huge, irregularly crescentic pile of debris known as the terminal moraine.” We might add to this the term ground moraine, which refers to a thinner veneer of glacial till laid down over a broad area. Spectacular nested lateral and end moraines extend out from the eastern front of the Sierra Nevada at Lee Vining Canyon. Lakes are found occupying the valleys behind many of these landforms. Kettle Moraine State Forest, northwest of Milwaukee, Wisconsin, is also the site of numerous moraines. On the other side of the country, Cape Cod owes its shape to the terminal moraine there, though some of the cape’s outlines have been modified by waves.

Robert Hass