Upper Mesa Falls is a waterfall

Waterfall

A waterfall is a place where flowing water rapidly drops in elevation as it flows over a steep region or a cliff.-Formation:Waterfalls are commonly formed when a river is young. At these times the channel is often narrow and deep. When the river courses over resistant bedrock, erosion happens...

 on the Henrys Fork in the Caribou-Targhee National Forest

Caribou-Targhee National Forest

Caribou-Targhee National Forest is located in the states of Idaho and Wyoming, with a small section in Utah in the United States. The forest is broken into several separate sections and extends over . To the east the forest borders Yellowstone National Park, Grand Teton National Park and...

. Upstream from Lower Mesa Falls

Lower Mesa Falls

Lower Mesa Falls is a 65-foot-high waterfall on the Henrys Fork in Caribou-Targhee National Forest. It is downstream of Upper Mesa Falls....

, it is roughly 16 miles away from Ashton, Idaho

Ashton, Idaho

Ashton is a city in Fremont County, Idaho, United States. It is part of the Rexburg, Idaho Micropolitan Statistical Area. The population was 1,129 at the 2000 census. The district is noted for seed potato production and bills itself as the world's largest seed potato growing area.-Geography and...

.

Upper Mesa Falls is roughly 114 feet high and 200 feet wide.

Formation

Mesa Falls Tuff

Tuff

Tuff is a type of rock consisting of consolidated volcanic ash ejected from vents during a volcanic eruption. Tuff is sometimes called tufa, particularly when used as construction material, although tufa also refers to a quite different rock. Rock that contains greater than 50% tuff is considered...

, which is the rock over which Upper Mesa Falls cascades, was formed 1.3 million years ago. A cycle of rhyolitic

Rhyolite

This page is about a volcanic rock. For the ghost town see Rhyolite, Nevada, and for the satellite system, see Rhyolite/Aquacade.Rhyolite is an igneous, volcanic rock, of felsic composition . It may have any texture from glassy to aphanitic to porphyritic...

 volcanism from the Henrys Fork caldera

Caldera

A caldera is a cauldron-like volcanic feature usually formed by the collapse of land following a volcanic eruption, such as the one at Yellowstone National Park in the US. They are sometimes confused with volcanic craters...

 deposited a thick layer of rock and ash across the area. This layer compressed and hardened over time.

Between 200,000 and 600,000 years ago, the river eroded a wide canyon which was subsequently partly filled with basalt

Basalt

Basalt is a common extrusive volcanic rock. It is usually grey to black and fine-grained due to rapid cooling of lava at the surface of a planet. It may be porphyritic containing larger crystals in a fine matrix, or vesicular, or frothy scoria. Unweathered basalt is black or grey...

lava flows. The Henrys Fork of the Snake River then carved the channel through the basalt; which is the inner canyon seen today.

External links

• Mesa Falls Recreation Area (USDA Forest Service - Caribou-Targhee National Forest)