Wikipedia:Today's featured article/December 6, 2004

The geology of the Zion and Kolob canyons area includes nine known exposed formations, all visible in Zion National Park in Utah, United States, and representing about 150 million years of mostly Mesozoic-aged sedimentation. Part of the Grand Staircase, the formations exposed in the Zion and Kolob area were deposited in several different environments that range from warm shallow seas, streams, and lakes to large deserts and dry near-shore environments. Subsequent uplift of the Colorado Plateaus exposed these sediments to erosion by swifter streams that preferentially cut through weaker rocks and jointed formations. Much later, lava flows and cinder cones covered parts of the Zion area. Zion National Park is situated on an elevated plateau that consists of sedimentary formations that dip very gently to the east. This means that the oldest strata are exposed along the Virgin River in the Zion Canyon part of the park and the youngest are exposed in the Kolob Canyons section. The plateau is bounded on the east by the Sevier Fault Zone, and on the west by the Hurricane Fault Zone. Weathering and erosion along north-trending faults and fractures influence the pattern of landscape features associated with canyons in this stream-incised plateau region. (more...)

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