![]() ![]() Large landslides occurred and the remains of these slides (huge chunks of basalt and andesite) mantle the slopes of Boulder and Thousand Lakes Mountains. Many of the boulders are angular in shape, whereas rocks rolled by streams become rounded. Recent studies show that the glaciers were small and the streams lacked the power to move boulders nine feet or more in diameter such as those found around Fruita. Geologists long thought the boulders had moved from Boulder Mountain in Ice-Age glaciers and streams that carried the rocks down valley. They originated in the high basalt and andesite cliffs that edge Boulder Mountain and the Thousand Lakes Mountain plateaus west of the park. The boulders are striking among the tilted red and white bands of sandstone and shale that form the Waterpocket Fold. In the Fremont River Valley they cover Johnson Mesa above the campground and scatter the hillsides of Fruita. Large black boulders are strewn along several valleys that cross Capitol Reef National Park. They are newcomers to the park landscape, and continue to move through waterways during flash floods. Black boulders are an indication of geology in action.
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