During What Time Did The Western U.S. Experience A Large Amount Of Crustal Extension?

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What causes crustal extension?

When the pressure from the Farallon Plate went away the huge Andes-like mountain range collapsed of its own weight and spread out to the west starting about 17 million years ago. This spreading is called crustal extension. Crustal extension caused massive blocks of crust to settle.

What caused Basin and Range extension?

The basins (valleys) and ranges (mountains) are being created by ongoing tension in the region pulling in an east-west direction. Over most of the last 30 million years movement of hot mantle beneath the region caused the surface to dome up and then partially collapse under its own weight as it pulled apart.

What faults are in the Basin and Range Province?

The Basin and Range Province includes much of western North America. In the United States it is bordered on the west by the eastern fault scarp of the Sierra Nevada and spans over 500 miles (800 km) to its eastern border marked by the Wasatch Fault the Colorado Plateau and the Rio Grande Rift.

Why is the Basin and Range crust thin?

Crustal extension causes the thinning and deformation of the upper crust in an orientation perpendicular to the direction of extension. … Extension causes the plate to stretch fracture and thin. Mountains rise and valleys drop over a long period of time creating what we see as basin and range topography.

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Where does extensional deformation occur?

Continental Rifting

Continental Rifting occurs where continental crust is undergoing extensional deformation. This results in thinning of the lithosphere and upwelling of the asthenosphere which results in uplift.

Where does crustal divergence extension occur?

Divergent plate boundaries are zones where plates split into two or more smaller plates that move apart and the dominant stress field is extension. To accommodate the separation dominantly normal faults and even open fissures form where crustal rocks undergo stretching rupture and lengthening.

When was the Basin and Range formed?

However the majority of the extension occurred around 20 ±10 million years ago. The extensional provinces in the northern part of the Basin and Range started generally earlier while the southern portion (especially south of 40° north latitude) mostly started later around 30 million years ago.

How long is the San Andreas Fault?

San Andreas Fault/Length
The entire San Andreas fault system is more than 800 miles long and extends to depths of at least 10 miles within the Earth. In detail the fault is a complex zone of crushed and broken rock from a few hundred feet to a mile wide.Nov 30 2016

How much extension has occurred in the Basin and Range?

In the Basin and Range the crust has been stretched by up to 100% of its original width. As a result of this extension the average crustal thickness of the Basin and Range region is 30 – 35 kilometers (19 – 22 miles) compared with a worldwide average of around 40 kilometers (25 miles).

Why does the Basin and Range Province in western North America have north south trending mountain ranges separated by desert valleys?

Active earthquakes active faults. accommodate the stress/strain of extension. … Along these roughly north-south-trending faults mountains were uplifted and valleys down-dropped producing the distinctive alternating pattern of linear mountain ranges and valleys of the Basin and Range province.

When was San Andreas fault formed?

about 30 million years ago
The San Andreas Fault was born about 30 million years ago in California when the Pacific Plate and the North America plate first met. Before then another oceanic plate the Farallon plate was disappearing beneath North America at a subduction zone another type of plate boundary.Mar 10 2015

What is the climate of the basin and range?

Temperature: Summer temperatures in the Southern Basin and Range often measure 100 degrees F or more. Winter temperatures are mild with few nights falling below freezing. … Geology: The basin and range topography of the southern portion of the Southwest results in heavy erosion and accumulation of alluvial sediments.

Is Death Valley in basin and range?

With its exposed terrain and extreme changes in elevation Death Valley is one of the best places to witness basin and range topography and there’s no better vista than from Dante’s View a 1 600-meter-high overlook perched atop the Black Mountains in the Amargosa Range.

When was Death Valley formed?

It is apparent that there has not always been a valley here. Death Valley’s oldest rocks formed at least 1.7 billion years ago are so severely altered that their history is almost undecipherable.

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What do we mean by alternating mountains and valleys?

Stress and Mountain Building

Subduction of oceanic lithosphere at convergent plate boundaries also builds mountain ranges. When tensional stresses pull crust apart it breaks into blocks that slide up and drop down along normal faults. The result is alternating mountains and valleys known as a basin-and-range.

How are extensional basins formed?

When a strike-slip fault is offset along strike such as to create a gap e.g. a left-stepping bend on a sinistral fault a zone of extension or transtension is generated. Such bends are known as releasing bends or extensional stepovers and often form pull-apart basins or rhombochasms.

What are extensional basins?

Extensional basins such as the passive margin basins on both sides of Atlantic Ocean Continental and Oceanic basins in the Aegean Region and mainly continental basins of the Basins and Ranges contain very valuable earth resources such as oil and gas precious metals and borate mineral.

What extensional means?

1 : of relating to or marked by extension specifically : denotative. 2 : concerned with objective reality. Other Words from extensional Example Sentences Learn More About extensional.

What is an extensional plate boundary?

Three main types of plate boundaries: Divergent: extensional the plates move apart. Spreading ridges basin-range. Convergent: compressional plates move toward each other.

What extensional tectonic process will form mountains?

When plates collide or undergo subduction (that is – ride one over another) the plates tend to buckle and fold forming mountains. Most of the major continental mountain ranges are associated with thrusting and folding or orogenesis.

What type of fault would most likely be found in an extensional environment?

An extensional fault is a fault caused by stretching of the Earth’s crust. Stretching reduces the thickness and horizontally extends portions of the crust and/or lithosphere. In most cases such a fault is also a normal fault but may create a shallower dip usually associated with a thrust fault.

Which geographical region is located west of the Great Plains and east of the Basin and range?

The Interior Lowlands are located west of the Appalachian Mountains and east of the Great Plains. There are rolling flatlands with many rivers broad river valleys and grassy hills.

Where is the Basin and range region?

The Basin and Range province is familiar to anyone lucky enough to venture across it. Steep climbs up mountain ranges alternated with long treks across flat basins. This pattern extends from eastern California to central Utah and from southern Idaho to the state of Sonora in Mexico.

How large is the Basin and range?

The basins are generally 4 000–5 000 feet (1 200–1 500 m) above sea level and the mountain ranges rise 3 000–5 000 feet above the level of the basins. Joshua tree (Yucca brevifolia) in the Basin and Range Province Nevada U.S. The northern half of the province is called the Great Basin (q. v.).

When was the last time San Andreas Fault moved?

There are only two large known historic earthquakes on the San Andreas Fault in southern CA the most recent in 1857 and before that one in 1812. With about 45 years between the historic earthquakes but about 160 years since the last one it is clear that the fault does not behave like a clock with a regular beat.

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Is California going to sink?

No California is not going to fall into the ocean. California is firmly planted on the top of the earth’s crust in a location where it spans two tectonic plates. … The strike-slip earthquakes on the San Andreas Fault are a result of this plate motion.

Can the San Andreas Fault cause a 9.0 earthquake?

The San Andreas fault is not long and deep enough to have a magnitude 9 or larger earthquake as depicted in the movie. … Computer models show that the San Andreas fault is capable of producing earthquakes up to about magnitude 8.3.

What causes basin and range topography quizlet?

What causes basin and range topography? Tension and faulting on large rock masses.

How do you describe the range and basin?

In geology a basin is defined as a bounded area where the rock within the boundaries dips inward toward the center. By contrast a range is a single line of mountains or hills forming a connected chain of land higher than the surrounding area.

What is the Basin and Range for kids?

The Basin and Range Province is a vast geographic region in the west United States and northwest Mexico. It has narrow faulted mountain chains and flat arid valleys or basins. … There are many ecoregions but the lower part is mostly desert.

What is a basin in the West Region?

The Great Basin broadly speaking is a geographic area between the Sierra Nevada mountains on the west the Rocky Mountains on the East the Snake River on the North and the Sonoran/Mojave Deserts to the south.

Is the Basin and Range province volcanically active?

Large volume volcanic eruptions in the Basin and Range Province include Basin and Range eruptions in California Idaho Colorado New Mexico Texas Arizona Nevada Wyoming and Oregon as well as those of the Long Valley Caldera geological province and the Yellowstone hotspot.

Which American state is entirely made up of Basin and Range Desert?

Nevada is the only state to be characterized entirely by basin and range topography which comprises narrow alternating north-south trending mountain ranges and intervening basin valleys. This topography makes Nevada the most mountainous state in the country (NPS 2015).

What is the dip of San Andreas Fault?

The earthquake hypocenter occurred at a depth of 11 miles (18 km) located approximately 4 miles west of the surface trace of the San Andreas Fault (the fault plane dips at an angle of about 75 degrees to the west).

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