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The Grand Canyon of the Yellowstone and the Lower Falls.
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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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