The majority of Mt. Everts is made of
Cretaceous era sediments. The
Cretaceous Interior Seaway deposited sediments across North America from 120 to 70 million years ago. The first of these deposits in the Yellowstone region was the
Telegraph Creek formation (100 mya) and is predominantly shale. The Eagle formation (75 mya) is dominated by sandstone and was deposited in shallower water along deltas and beaches. The Everts formation (70 mya) is dominated by sandstone and has coal seams from plant debris that collected in swampy areas. There are no rocks on Mt. Everts from 65 to 2.1 million years ago. The absence of rocks is called an unconformity. During this period few or no rocks were deposited, and erosion carried away any sediments that were deposited. The eruption of the Yellowstone hot spot 2.1 million years ago deposited the Huckleberry Ridge
tuff on the southern part of Mt. Everts. It is the youngest rock on the mountain. The tuff was made by multiple eruptions around 2.1 million years ago. Ash fall from the earliest part of the eruption was deposited first and can be seen as a thin strip of white rock eight feet tall. This air fall ash was so hot that it baked the sedimentary rocks it covered. The sedimentary rocks turned a darker shade of red because the heat caused red iron oxide minerals to form. Next,
pyroclastic flows moved through the region, sometimes at speeds of hundreds of miles per hour, depositing the bulk of the Huckleberry Ridge tuff. The tuff was originally deposited evenly across the area when the region was lower than surrounding hills. Deposits from streams just beneath the Huckleberry Ridge tuff show that this area was at a low elevation just before the eruption. A combination of thermal bulging and erosion caused Mt. Everts to rise 1600 feet in the last 2.1 million years. This is called
topographic inversion, because the lower areas become the higher areas. Thermal bulging related to the Yellowstone hot spot caused the bulk of the uplift. Erosion of surrounding areas also deepened nearby canyons because the tuff is harder, and therefore more resistant to erosion, than the other rocks. ==Gallery==