What causes crustal extension?
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.
Where do we see crustal extension?
Crustal Extension. Image at right shows in the upper half the NE-SW trending mountain ranges and valleys of the basin and range province, whereas map at left shows the names of features and indicates location in SE California. The ranges and valleys in the lower half of the picture (Death Valley, Panamint Range, etc.)
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.
What is plate tectonics extension?
Extensional tectonics is concerned with the structures formed by, and the tectonic processes associated with, the stretching of a planetary body’s crust or lithosphere.
What is continental extension?
Extension of overthickened continental crust is commonly characterized by an early core complex stage of extension followed by a later stage of crustal-scale rigid block faulting.
What is extension geology?
n. 1. a gap or space made by cleaving or splitting; fissure. 2. ( Geological Science) geology a long narrow zone of faulting resulting from tensional stress in the earth’s crust.
In which 2 places do divergent boundaries occur?
Divergent boundaries are occur in oceans and lower mantle.
Where are most divergent boundaries located?
mid-ocean oceanic ridges
Most divergent boundaries are located along mid-ocean oceanic ridges (although some are on land). The mid-ocean ridge system is a giant undersea mountain range, and is the largest geological feature on Earth; at 65,000 km long and about 1000 km wide, it covers 23% of Earth’s surface (Figure 4.5. 1).
What happens at a continental rift zone?
Continental Rift: Topography, Earthquakes, and Volcanism Ripping a tectonic plate apart elevates the region and causes earthquakes, volcanic eruptions and the formation of long mountain ranges separated by broad valleys (basins). Only shallow earthquakes occur beneath the Basin and Range Province and Rio Grande Rift.
What are continental rifts formed by?
Rifting can be caused when hot material from a mantle plume reaches the base of a continental plate and causes the overlying lithosphere to heat up. In addition to this the uwards movement of the plume against the base of the plate results in extensional forces, which can cause rifting.
What is extension theory?
Extension Theory can be defined as studying extensions of maps from topological spaces to metric simplicial complexes or CW complexes. It is shown that several concepts of set-theoretic topology can be naturally introduced using ideas of Extension Theory.
Why is block faulting with extension?
Tilted block faulting, also called rotational block faulting, is a mode of structural evolution in extensional tectonic events, a result of tectonic plates stretching apart. When the upper lithospheric crust experiences extensional pressures, the brittle crust fractures, creating detachment faults.
How does McKenzie’s model of continental extension work?
McKenzie’s model of extension assumes instantaneous rifting (i.e. duration of rifting = 0) which produces an initial subsidence (S i ) and passive upwelling of hot asthenosphere that results in a thermal perturbation. As this thermal anomaly decays thermal subsidence occurs.
Which is the best model for extensional tectonics?
There are largely two main models when considering extensional tectonics, both offering quite different proposals. The McKenzie model incorporates pure shear, while the Wernicke model is based upon a simple shear regime.
Which is a secondary process in continental extension?
3.3 Introduction to models of continental extension Passive rifting: Tensional stresses in the continental lithosphere cause it to fail, allowing hot mantle rocks to penetrate the lithosphere. Crustal doming and volcanic activity are only secondary processes.
What does the flexural cantilever model take into account?
The flexural cantilever model takes into account that with tectonic extension there would be several large faults all producing flexure, and that there would be areas of overlapping deformation.