A Plain of Volcanoes
The shallow arc of Idaho's Snake River Plain spans southern Idaho, gently
rising from west to east. Current theories suggest that the plain marks the
path of continental movement over a deep hotspot now lying beneath the
Yellowstone Plateau. As the continent drifted southwestward over millions of
years, colderas-super-volcanoes 10-40 miles (15 - 64 km) wide-erupted
over the hotspot.
In the past 17 million years, there have been about a dozen catastrphic
eruptions releasing huge volumes of rhyolitic magma and ash. Between these
super-eruptions were long periods when more fluid basaltic lava flowed from
more than 8,000 shield volcanoes and numerous lava cones. Remnants of
these dot the Eastern Snake River Plain today. Layer upon layer of basalt
flows extend 3,000 - 6,000 fet (1,000 - 2,000 m) below the surface,
completely covering the rhyolite “basement.”
Sinking Rivers And
A Flowing Aquifier
Streams that flow here are indirect
tribulations to the Snake River. The
aptly named Lost River flows to an
area north of here known as “the
sinks” where it soaks into the
ground, becoming part of an aquifer
the volume of Lake Erie. The aquifer
flows through pores and fractures in
the rock hundreds of feet beneath
the surface, eventually emerging
from springs along the Snake River
Canyon at Thousand Springs about
100 miles (160 km) to the southwest.
[Picture Captions]
Big Southern Butte
Big Southern Butte, rising
2,500 feet (760 m) above
the Eastern Snake River Plain,
is a prominent reminder of
the region's volcanism. About
300,000 years ago, the butte
intruded through surrounding
layers of basalt, rising to an
elevation of 7,560 feet
(2,300 m). It is one of the
largest composite rhyolite
domes in the world.
Ancinet calderas are evidence of the North American
Continental's mvement over the Yellowstone hotspot.
When Yellowstone Caldera erupted 640,000 years ago,
it released about 240 cubic miles (1,000 km) of material,
covering half of North America in 6 feet (2 m) of debris.
Niagara Spings is located at
Thousnd Springs State Park
near Hagerman, Idaho.
