Yellowstone is roughly the size of Connecticut.
Yellowstone National Park was established in 1872 as the world’s first national park. Located in Wyoming, Montana and Idaho, Yellowstone covers 2,221,766 acres, making it roughly the size of Connecticut. Yellowstone is famous for its geysers, wildlife and natural scenery. Yellowstone has a wealth of geological features that scientists find interesting and educational.
Geysers, Hot Springs and Fumaroles
Yellowstone is famous throughout the world for its geysers–especially Old Faithful. Because of the volcanic activity under the area, Yellowstone has more than 300 geysers and many of them change their activity regularly. Fumaroles are similar to geysers, except they emit steam instead of water. Fumaroles can be so forceful that they cause the ground to shake and make a sound like thunder. Hot springs are the same as geysers, except they don’t erupt. Visitors are able to relax in some of the hot springs, but many of the Yellowstone hot springs are boiling hot and should be avoided.
Paleozoic and Mesozoic Development
The Yellowstone basement complex of rock was created during the Precambrian period and is composed of gneiss and schist. The middle and late Cambrian periods are when the huge amounts of limestone, shale and sandstone began to form, and they continued to develop all the way into the late Mesozoic era. During the Mississippian and Permian epochs, some dolomite was formed, but it was rare and sparsely distributed. Northwestern Yellowstone began seeing its first basalt lava flows during the late Cretaceous period.
The Tertiary period of the Cenozoic era began to see massive volcanic rock deposits all over Yellowstone. It was during this period that the Absaroka Volcanic Supergroup was formed. The famous fossil trees at Yellowstone’s Specimen Ridge were formed during this time and the rock formations from this period are primarily andesites and volcaniclastics. The rocks from this era are the most accessible and visible, making it the most important era for lay geologists.
Huckleberry Ridge, Mesa Falls and Lava Creek Tuffs
Yellowstone is the home of three massive eruptions that helped to shape the geology of most of the western United States. The first, Huckleberry Ridge, happened 2.1 million years ago and was 2,400 times larger than the 1980 Mount St. Helens eruption. Remnants from this explosion can be found as far away as California, the Gulf of Mexico and Saskatchewan, Canada. The second, Mesa Falls, happened 1.3 million years ago and was relatively small in comparison. The third, Lava Creek, began 1.2 million years ago and had three eruptive pulses–150,000, 110,000 and 70,000 years ago. The rock produced from Lava Creek covers about 240 cubic miles.
Glacial and Surficial Activity
The top layer of rock in Yellowstone was deposited by glaciers, hydrothermal explosions, hot springs, cemented ice and detritus. Much of what was deposited is sediments and a large amount of basalt and rhyolite. Hot spring and hydrothermal activity is responsible for dissolving Paleozoic and Mesozoic limestone deposits and redistributing the rock back to the surface. Geyserite (hydrous silicon dioxide) is a rock that is similar to opal and is constantly forming because of the underground volcanic activity in Yellowstone. In the Mammoth Springs area of Yellowstone, travertine can be found and is still forming.