Travel Reference
In-Depth Information
The thermal features in Yellowstone are an indication of the region's volcanic past,
present, and future, and as such they are in constant states of change. Small but daily earth-
quakes cause shifts in activity and temperature. The travertine
Mammoth Terraces
are lit-
erally growing and changing on a daily basis to the point that the boardwalks have had to
be altered to protect visitors from different flows of searing hot water.
YELLOWSTONE'S SUPERVOLCANO
It's always interesting to watch visitors' expressions when you tell them that in Yel-
lowstone National Park they are standing atop one of the world's largest active super-
volcanos . . . and that it is overdue for an apocalyptic eruption. While these facts are
true, the reality is much less threatening. Indeed there have been three phenomenal
eruptions over the course of the last two million years, and the patterns do indicate
that the volcano is overdue to erupt. But scientists agree that the chances of a massive
eruption in the next 1,000 or even 10,000 years are very slight. For the time being,
anyway, the supervolcano that gives rise to Yellowstone's extraordinary geothermal
features is all bark and no bite—thankfully.
The first supervolcanic eruption 2.1 million years ago was 6,000 times more
powerful than the 1980 eruption of Mount St. Helens, spouting rock and ash in every
direction from Texas to Canada, Missouri to California. The eruption emptied the
magma chamber located just underneath the park and caused a massive sinking of
the earth, known as a caldera, within the confines of what is now the park. Small
lava flows filled in the perimeter of the Huckleberry Ridge Caldera over the course
of hundreds of thousands of years.
The second major, but smaller, eruption occurred 1.3 million years ago and cre-
ated the Henry's Fork Caldera. The most recent massive eruption took place roughly
640,000 years ago and created the Yellowstone Caldera, which is 30 by 45 miles in
size. The perimeter of the Yellowstone Caldera is still visible in places throughout
the park. Hike up Mount Washburn on Dunraven Pass between Canyon and Tower,
look south, and you will see the vast caldera formed by the most recent eruption. The
caldera rim is also visible at Gibbon Falls, Lewis Falls, and Lake Butte. As you drive
between Mammoth and Gardiner, look at Mount Everts to the east and you will see
layers of ash from the various eruptions.
