Where are Ophiolites formed?
Where are Ophiolites formed?
Ophiolites may have formed either at divergent plate boundaries (mid-oceanic ridges) or convergent plate boundaries (supra-subduction zones; i.e. island arcs and marginal basins). They are called MOR and SSZ types, respectively.
Where do Ophiolites form and what tectonic environment do they represent?
… ultramafic rocks are known as ophiolites. Many geologists believe that ophiolites formed at oceanic ridges were emplaced by tectonic forces at convergent plate boundaries and then became exposed in highly deformed orogenic (mountain) belts.
How did the Troodos ophiolite form?
Troodos formed at the bottom of the Tethys Ocean during the Cretaceous around 92 Myrs ago. These deposits form at spreading ridges deep on the seafloor through the interaction of super-heated seawater with igneous rocks deep within the oceanic crust.
What rocks form at subduction zones?
Subducting slabs are composed of basaltic crust topped with pelagic sediments; however, the pelagic sediments may be accreted onto the forearc-hanging wall and not subducted. Most metamorphic phase transitions that occur within the subducting slab are prompted by the dehydration of hydrous mineral phases.
Which type of earthquake tends to be the most damaging for humans?
Shallow quakes generally tend to be more damaging than deeper quakes. Seismic waves from deep quakes have to travel farther to the surface, losing energy along the way.
What are P and S-waves?
P-waves are compression waves that apply a force in the direction of propagation. On the other hand, S-waves are shear waves, which means that the motion of the medium is perpendicular to the direction of propagation of the wave. The energy is thus less easily transmitted through the medium, and S-waves are slower.
In what country was the largest earthquake ever recorded?
What happens to P and S waves as they travel inside Earth?
The speed of P waves and S waves increases as they travel deeper into the Earth’s mantle . They travel through the Earth in curved paths, but they change direction suddenly when they pass through the boundary between substances in different states.
Why can both P and S waves travel through the mantle?
Figure 19.2a: P-waves generally bend outward as they travel through the mantle due to the increased density of mantle rocks with depth. The bending of seismic waves is called refraction. 6. Figure 19.2b: S-waves do not travel through the outer core, creating an even bigger shadow zone for S-waves.
What proves the existence of the boundary between the crust and the mantle?
The Moho is the boundary between the crust and the mantle in the earth. This is a depth where seismic waves change velocity and there is also a change in chemical composition. Also termed the Mohorovicic’ discontinuity after the Croatian seismologist Andrija Mohorovicic’ (1857-1936) who discovered it.
What are the approximate velocities of P & S waves at the bottom of the mantle?
Compression waves and shear waves travel very quickly through geological materials. As shown in Figure 9.5, typical P-wave velocities are between 0.5 km/s and 2.5 km/s in unconsolidated sediments, and between 3.0 km/s and 6.5 km/s in solid crustal rocks.
Do S waves travel through the mantle?
S-waves can travel only through solids, because only solids have rigidity. Because the earth’s mantle becomes more rigid as its depth below the asthenosphere increases, S-waves travel faster as they go deeper in the mantle.
Why do S waves not travel through liquid?
S-waves cannot travel through liquids. When they reach the surface they cause horizontal shaking. Liquids don’t have any shear strength and so a shear wave cannot propagate through a liquid. Think of a solid material, like a rock.