Travel Reference
In-Depth Information
But heat isn't everything. Essential to Yellowstone's thermal features is the addition of
water, falling onto the park as rain or, more commonly, snow. This surface water may seep
down as deep as 2 miles over long periods of time before it drains through the side chan-
nels of geysers, hot springs and underground aquifers. The next time you watch a geyser,
remember that the water spurting out may have fallen as snow or rain up to 500 years ago.
With the plumbing of Yellowstone's geothermal features constantly in flux, what seem
like permanent features are mere blips on the geologic timescale. Geysers suddenly erupt,
or dry up; hot springs gradually appear, or explode so violently that they destroy them-
selves.
Scientists are only beginning to fathom these
complex underground systems, but it's clear
that this is a threatened landscape unless the
broader region is safeguarded thoughtfully.
Through conservation, Yellowstone protects
about half of the world's geysers, but in areas
like Iceland and New Zealand, where geo-
thermal features have been developed as energy sources, geysers and geothermal activity
may be altered or cease altogether.
Oil, gas, and groundwater development near the
park and drilling in Island Park, Idaho, and Corwin
Springs, Montana, have the potential to alter the
natural function of geothermal systems in the park.
Geysers
Only a handful of Yellowstone's thermal features are active geysers (from the Icelandic
geysir,
meaning 'to gush or rage'), but these still comprise about 50% of the global total,
making the park a globally significant resource.
How do geysers form? First, snowmelt trickles down into hot rock where it is super-
heated. The heated water begins to rise, creating convection currents. The earth acts like a
giant pressure cooker, keeping the water liquid even though it reaches temperatures of
over 400°F. As the water rises, it dissolves silica trapped in the surrounding rhyolite rock
base. At the surface this silica is deposited as the mineral sinter (geyserite), creating the
familiar ash-colored landscape of Yellowstone's thermal basins.
What gives geysers their 'oomph' is the sinter seal that junks up the escape valves in
geyser chambers. This temporary blockage causes an intense buildup of gas until the seal
breaks and releases the accumulated pressure. As the superheated water rushes toward the
surface, water pressure drops and the water expands more than 1500 times in a violent
chain reaction as it flashes into steam and explodes into the sky. Geysers require walls of
hard rock like rhyolite, which is part of the reason why Yellowstone's geysers are concen-
trated in the southwest of the park.
