Each year, more than three million visitors travel to Yellowstone National Park to admire its splendor, including numerous thermal pools, thousands of steaming geysers, fumaroles, and bubbling mudpots. However, this beauty masks one of the largest and most destructive forces on our planet – a major volcanic system of Yellowstone supervolcano. Hidden under the ground, this powerful volcanic, hydrothermal, and tectonic force–from Yellowstone volcanoes activity to earthquakes, erosion, and glaciers–continually re-shapes the dynamic landscape of this beautiful America’s first national park. The evidence for this underground activity includes thousands of earthquakes per year (up to magnitude 3.3, but in most cases, these earthquakes are too small to be felt), subsidence and uplift of the ground surface, as well as persistent hydrothermal activity. Eventually, it is very likely that these changes can culminate in another volcanic eruption or a large earthquake, both of which have frequently occurred in the geologic past of Yellowstone National Park.
To assess the potential hazards from volcanic eruptions and future earthquakes, scientists from the University of Utah and the US Geological Survey are working together to provide the most up-to-date reports on Yellowstone volcanoes activity.
Yellowstone Caldera
The Yellowstone Plateau is situated between the Northern and Middle Rocky Mountains and lies in the middle of one of the largest volcanic fields on our planet, dating back to 2.5 million years ago. The major eruptions of Yellowstone volcanoes were very voluminous. However they resulted in superficial expressions of magma and in several places affected high crustal levels. Since 2.5 million years ago, the total amount of magma erupted from the Yellowstone volcanoes approaches to 6,000 cubic kilometers.
With so much magma erupted from the volcanoes, enormous calderas associated with a very subtle morphology were produced. The youngest of three nested calderas is the Yellowstone caldera, one of the largest and most active calderas on Earth. It is an elliptical depression in about 80 kilometers in length and 50 kilometers in widths and occupies much of Yellowstone National Park.
The two older calderas form a part of a circular basin at the west edge of the Yellowstone Plateau and are called Island Park.
Yellowstone Caldera features world’s most spectacular geysers, bubbling mudpots and boiling geysers that have made Yellowstone National Park so famous. Even the Grand Canyon owes its existence to the tremendous forces of Yellowstone volcanoes that affected the region during the past 2 million years. Although the latest eruptions were nearly 70,000 years ago, such immense hydrothermal activity indicates that magma is very close to the surface at the Yellowstone caldera, which means that the crust is still restless. According to surveys, in the center of the caldera area rose up to 86 centimeters between 1923 and 1984 and then it slightly subsided between 1985 and 1989. Scientists hesitate about the cause of this surface instability and presume that it is related to the withdrawal or addition of magma beneath the caldera surface. Furthermore, Yellowstone National Park and the areas west to the park are historically considered to be the most seismically active regions in the Rocky Mountains. Beneath the entire caldera small earthquakes are common, but most are felt in the area close to Hebgen Lake, where a magnitude 7.5 earthquake occurred in 1959.
Volcanic History Overview
The Yellowstone Plateau was shaped through three volcanic cycles that span 2 million years, including some of the largest known eruptions in the world. About 2.1 million years ago, an eruption of more than 2,450 cubic kilometers Huckleberry Ridge Tuff created a 75 kilometer-long caldera known as Island Park. The second eruption of the Mesa Falls Tuff occurred around 1.3 million years ago and developed the Henrys Fork caldera, which is about 16 kilometer-wide. Subsequently, the volcanic activity turned to the present Yellowstone Plateau and in 640,000 years ago culminated with the eruption of more than 1,000 cubic kilometers of Lava Creek Tuff, which formed the present Yellowstone caldera, 45 kilometers-wide and 85 kilometers-long. Between 150,000 and 70,000 years ago, voluminous rhyolitic lava flows (more than 1,000 cubic meters) were erupted. Since the late Pleistocene, there were no magmatic eruptions. However, near Yellowstone Lake large eruptions occurred during the Holocene. The magmatic heat powering the past eruptions still fuels the park’s geysers, fumaroles, hot springs, and mudpots. And the spectacular Grand Canyon provides a glimpse on our planet’s interior: the boundaries of lava flows are highlighted with magnificent waterfalls. Rugged mountains reward both eye and spirit.