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How did faulting create the mountain ranges and basins of the Basin and Range Province?
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North American Desert
Physical features of western North America.
The Basin and Range Province was shaped by large-scale crustal extension, a process that began over 40 million years ago and accelerated significantly about 15 million years ago. This extension caused the Earth's crust to lengthen, leading to the formation of normal faults.123
Through this faulting, the crust was broken into a series of blocks that were either uplifted or dropped downward. This created a characteristic horst and graben topography:42
- Horsts: These are blocks of crust that were relatively uplifted between normal faults, forming the mountain ranges that trend roughly north-south.43
- Grabens: These are blocks that dropped downward between normal faults, forming the flat, sediment-filled basins that separate the ranges.423
Over time, these features have been further modified by erosion and the accumulation of alluvial debris within the basins. This tectonic process remains active today, with basins continuing to deepen and mountain ranges increasing in height.41