WASATCH RANGE

Have you ever seen the dramatic mountain range just east of Salt Lake City, Utah? That's the Wasatch Range.

     The Wasatch Range is a classic example of fault-block mountains, which form by movement along faults in the Earth's crust.

     These mountains lie on the eastern edge of the Basin and Range Province, a geologically active region that Earth's forces are stretching east-west. This stretching, or extension, causes the Earth's crust to crack (fault) and break into blocks, some of which tilt and move—creating mountain ranges (uplifted blocks) and valleys (down-dropped blocks or basins). Most of the Basin and Range Province mountains, including the Wasatch Range, formed this way.

     Salt Lake Valley, where Salt Lake City is, and the Wasatch Mountains were once part of the same "piece" of Earth. But the stretching of the Earth's crust in the area caused a crack — or more precisely, a fault, which we call the Wasatch fault.

     As you know, cracks (faults) have two sides. The west side of the Wasatch fault is the crustal block where Salt Lake City sits today, and that crustal block sank, while the block on the east uplifted relative to the western block. The sunken western block became what we now refer to as Salt Lake Valley, and the uplifted eastern block became the Wasatch Mountains. Of course, wind, water, and ice sculpted the mountains into today's stunning vista.

     The Wasatch fault runs right along the base of the mountains, and you can see it in some places as a fault scarp or steep escarpment between 20 and 130 feet tall. It developed from both crustal blocks' incremental, frictional movements — the Wasatch block moving up and the Salt Lake Valley block moving down.