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Glacial horns, or pyramidal peaks, are formed when cirques, that are adjacent to one another, carve back into the headwall of the mountainside and form steep arétes. These peaks take on a pyramid shape. Probably one of the best known horns is the Matterhorn in the Swiss Alps. |
Ice tears and rips apart the rock as it moves over the surface of the mountain. Horns are formed as ice-filled cirques on opposite sides of the mountain grind back into the mountain, creating steep sided walls known as arétes. Points, or horns form on the ridges above and around the cirque ends.
Through thousands of years of multiple advances and retreats of the ice,
up and down the mountainside, rock is plucked up from the ground surfaces
and with it, scours other surfaces as the ice moves the material down the
slope. This scouring action leaves trails or scratches called striations
on the more resistant base rock. The direction of these scratches show the
direction of the ice flow.
As the rock is ground up, it takes on a fine, flour like consistency. Rock
flour loads the streams flowing out from under the glacier and ultimately
finds its way into local major drainages. In some cases these tributaries
take on a deep green, cloudy-like color. Between glacial periods during
some warming, this fine material can also be deposited on out wash plains
at the base of the glaciers. With the winds, it can be blown and deposited
(sometimes as dunes) miles away from the source if conditions are right.
This type of soil, known as Löess (pronounced lers), is extremely fertile.
Löess deposits are found throughout central Europe, in Northern China,
and in the Black Earth belt of the Ukraine. Extensive dunes are also found
in southeastern Washington State, in the Palouse growing region and through
the Midwest U.S.