Submitted by @askceil

During the last ice age over ten thousand years ago, huge glaciers in the Sierra Nevada carved out many lakes in the land surrounding Lake Tahoe. Glaciers moved down the V-shaped canyons on Lake Tahoe’s western side, scouring away rock and creating broad U-shaped valleys. These elongated depressions – Fallen Leaf Lake, Emerald Bay, Cascade Lake and others – filled with snowmelt water.

As glaciers carved their way through the earth surface then melted, they left behind deposits of soil, rock, and gravel. These ridges of debris are called moraines, a French word meaning “rubble heap.” The long ridge directly across Fallen Leaf Lake from Angora Lookout is a lateral, or side, moraine. It was formed by the debris the glacier deposited as it moved down the Glen Alpine Valley. Angora Lookout stands on a medial moraine, formed as two lateral moraines merged under the enormous pressures of two adjacent glaciers. One glacier came down Glen Alpine Valley, the other down Tahoe Valley.

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[inset photo caption] Lateral Moraine

[inset painting caption] Huge glaciers moved down the V-shaped canyons of the Sierra Nevada, carving away rock and creating broad U-shaped valleys.