Travel Reference
In-Depth Information
Hot spots may be fixed, but as the earth's crust moves over them, it forms a line of pro-
gressively newer volcanoes. The North American plate moves southwest one inch per
year. Its contact with the Yellowstone hot spot has burned a chain of volcanoes across the
West from southeastern Oregon (where it was active 16 million years ago) to northern
Wyoming (where it was last active 600,000 years ago). After a few million years, it will
slide over to North Dakota.
The Yellowstone region has been sitting atop this hot spot for about two million years,
with massive supervolcanic eruptions occurring roughly every 650,000 years. The last
three have been centered on Island Park, Henry's Fork and Yellowstone.
What do these eruptions entail? The most recent explosion formed the 1000-sq-mile
Yellowstone caldera at the center of the park 600,000 years ago. The explosion spat out
magma and clouds of 1800°F liquid ash at supersonic speeds, vaporizing all in its path
and suffocating the land in blisteringly hot ash flows. Billowing ash traveled thousands of
square miles in minutes, landing as far away as the Gulf of Mexico. The crater roof and
floor then imploded and dropped thousands of feet, creating a smoldering volcanic pit 48
miles by 27 miles wide. Ash circling the globe caused a volcanic winter by reducing the
amount of solar heat reaching the earth.
Visitors may be surprised that Yellowstone
is not more mountainous; the reason quite
simply is that the mountains were either blown
away by the explosion or sank into the caldera.
Since the explosion, at least 30 subsequent
lava flows, dating from 150,000 to 70,000
years ago, have filled in and obscured the cal-
dera, and forests have reclaimed the area,
though you can still make out the caldera in
numerous places. Turnouts on the road south
of Dunraven Pass provide excellent views of its northern part, and much of the caldera's
outline can be seen from the summit of Mt Washburn (
Click here
)
.
VOLCANOES
The Yellowstone Volcano Observatory, created in
partnership with the United States Geological Sur-
vey (USGS), monitors volcanic and earthquake un-
rest in the park. See their work at
ht-
Yellowstone's Thermal Features
Fueled by its underground furnace, Yellowstone is a bubbling cauldron of over 10,000
geothermal features - more than all other geothermal areas on the planet combined.
Maybe it isn't all that surprising. Magma, the earth's molten rock, is just 3 to 5 miles un-
derground, closer to the surface here than anywhere else on earth. The average heat flow
from the region is 40 times the global average.
