A Geologic History of Cache Valley

Rocks in nearby areas tell us that 50 million years ago, after the dinosaurs went extinct, a great mountain range lifted up. This early mountain range eroded away until today we find only a few places where it is still visible. Point of the Mountain, between Salt Lake City and Provo is one remnant. Another is at the base of the Oquirrh Mountains near Tooele.

Jump ahead 30 million years. 20 million years ago, another geologic force shook the western part of the North American continent. Geologists call this "Basin and Range faulting". This resulted in most of the mountains that we see around Utah and Idaho today.

As the mountains pushed up higher and higher, parts slid down in great landslides. One such landslide is a great "toe" of a hill just north of Smith and Edwards between Brigham City and Ogden. Other land slides resulted in some of the foothills around Cache Valley.

About 100,000 years ago the earth cooled and snow and ice spread south from the arctic. The mountains around the land that would become Cache Valley were covered by a great icecap. Tongues of glacier ice reshaped many of the mountains. Tony Grove lake is the remains of a glacier-shaped valley. as you approach Tony Grove Lake there is a "field" with large rocks. Such rocks are called glacier erratics, meaning they are moved from their origin and carried from a few feet to several miles.

Valleys are formed as glacier ice or water flows through the land. When a valley is formed by glaciers, it is U-shaped. When running water forms a valley, it is V-shaped. Many of the mountains around Cache Valley show U-shaped valleys (washes) near the summit leading to V-shaped washes further down the mountain.

This is a glacier valley on the south side of Logan Canyon, across from the Wind Caves. Notice the U-shaped valley.

As the icecaps and glaciers melted, Cache Valley became a lake. Eventually the lake covered most of Utah and parts of Idaho and Nevada. The lake is today called Lake Bonneville. Salt Lake is a small remnant of that once great lake.

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