Download Basin and Range Oquirrh mountains Salt flat Formation of basin and

Basin and Range
 Oquirrh mountains
 Salt flat
 Formation of basin and range province
o Compression, then stretching
o Normal faults and basin fill
 Salt lake valley the deepest basin – the valley is built atop over a mile of
sediments!
G.K. Gilbert Geologic Park
 The geologic park is named after a famous geologist
o American geologists, lived from 1843-1918
o Wrote about the geology of the Henry Mtns and named them, last
discovered and mapped moutain range in the continental US
o Discovered existence of Lake Bonneville and named it
o Wrote treatise on glaciation, worked in part with John Muir
 Kids read more at signs
Wasatch Fault
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Fault scarps v ancient shorelines
o Both along the east side of valley
o Shorelines form level terraces, fault scarps are more irregular
Bonneville shorelines
o Terraces at different levels tell us the lake varied in depth
o Lots of deposited gravels (see gravel pit)
Fault line
o The 240-mile-long fault is sectioned into 10 segments averaging 25
miles in length. Each segment can rupture independently. The
Wasatch fault has the dubious distinction of being one of the longest
and most active normal faults in the world.
o 1-in-7 chance of being hit by a magnitude-7.0 earthquake sometime in
the next 50 years
o Great Basin pulling away from us at a rate of ~.5 inches per year.
o the Salt Lake City segment of the fault has been expanding an
estimated 1.2 millimeters a year recently
o is it all bad?! No – the Wasatch fault was/is (still rising today)
instrumental in the creation of the Wasatch mountains. The reason
SLC is possible is because the mtns provide this otherwise dry, saline
valley with a fresh water supply.
o Also awesome scenery and recreation
o Regional restlessness in nearby Yellowstone National Park where a
concentrated plume of heat from deep within the earth is burning
through to the surface (called a hotspot ). As the North American plate
slowly moves southwestward over this stationary hotspot, a trail of
volcanic features is left in its wake (the Snake River Plain in southern
Idaho). Increased earthquake activity occurs in a U-shaped area
where the crust bulges and cracks as it encounters the hotspot. Faults
within the U-shape area surrounding the hotspot tend to be the most
active in the region. The Wasatch fault is the largest and most active of
these faults.
o complex zone of deformation comprised of many parallel faults.
Therefore "Wasatch fault zone."
o A single earthquake can produce scarps ranging from fractions of
inches to 20 feet high
 some scarps are over 100 feet high and represent multiple
surface-faulting earthquakes. The fault scarp along Wasatch
Boulevard just north of Little Cottonwood Creek in Salt Lake
County, is about 130 feet high.
Downtown
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Alta Club
o SE corner of E. S. Temple and State St.
o sandstone quarried about 5 miles northeast of Colton in Utah County.
This gray sandstone is part of the Eocene-age Colton Formation and is
composed of sediments deposited in a deltaic river system.
LDS temple
o Originally had a foundation of sandstone
 Foundation was laid, but buried to hide it during the Utah War
in 1857 to hide it from federal troops
 When they unburied the foundation, they found the sandstone
had cracked, so decided to change the material to quartz
monozite
 Very similar to granite (intrusive, igneous)
 Only diff is ratio of minerals that make up the rock (less
quartz)
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204 North State Street and state office of tourism
o nugget sandstone made into foundation and steps at the 205 N. State
St house built in 1890 and also the original SLC town hall, built 1864
(now office of tourism)
 nugget sandstone is what is left from one of the largest
dunefields ever to exist on planet earth!
 The sandstone for the town hall was quarried from Red Butte
canyon
Capitol Bldg
o Also quartz monzonite
 Eight hundred railroad carloads of rock from the Little
Cottonwood stock in Little Cottonwood Canyon, Salt Lake
County were used for the exterior.
 Many more interesting rocks represented inside