Welcome to the Grand Canyon of the Yellowstone. To navigate this
tour of canyon features, simply click 'Next Stop' at the bottom of each
page. If you prefer you may select features from the 'List of Stops'
or from the 'Interactive Map'.
About 600,000 years ago, huge volcanic eruptions occurred in Yellowstone,
emptying a large underground magma chamber. Volcanic debris spread for thousands of square
miles in a matter of minutes. The roof of this chamber collapsed, forming a giant
smoldering pit. This caldera was 30 miles (45 km) across, 45 miles (75 km) long, and
several thousand feet deep. Eventually the caldera was filled with lava.
One of these lava flows was the Canyon Rhyolite flow, approximately
590,000 years ago which came from the east and ended just west of the present canyon. A
thermal basin developed in this lava flow, altering and weakening the rhyolite lava by
action of the hot steam and gases. Steam rises from vents in the canyon today and the
multi-hued rocks of the canyon walls are also evidence of hydrothermally altered rhyolite.
Other lava flows blocked rivers and streams forming lakes that overflowed
and cut through the various hard and soft rhyolites, creating the canyon. Later the canyon
was blocked three different times by glaciers. Each time these glaciers formed lakes,
which filled with sand and gravel. Floods from the melting glaciers at the end of each
glacial period recarved the canyon, deepened it, and removed most of the sand and gravel.
The present appearance of the canyon dates from about 10,000 years ago
when the last glaciers melted. Since that time, erosional forces (water, wind,
earthquakes, and other natural forces) have continued to sculpt the canyon.
Grand Canyon of the Yellowstone Tour
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