There is no glacial evidence for continental movement in North America, because there was no ice covering the continent million years ago. North America may have been nearer the equator where warm temperatures prevented ice sheet formation. Mid-ocean ridges or spreading centers are fault lines where two tectonic plates are moving away from each other.
Mid-ocean ridges are the largest continuous geological features on Earth. They are tens of thousands of kilometers long, running through and connecting most of the ocean basins. Oceanographic data reveal that seafloor spreading is slowly widening the Atlantic ocean basin, the Red Sea, and the Gulf of California Fig. The gradual process of seafloor spreading slowly pushes tectonic plates apart while generating new rock from cooled magma. Ocean floor rocks close to a mid-ocean ridge are not only younger than distant rocks, they also display consistent bands of magnetism based on their age Fig.
Geomagnetic reversal allows scientists to study the movement of ocean floors over time. Paleomagnetism is the study of magnetism in ancient rocks. In other words, the particles will point in the direction of the magnetic field present as the rock was cooling. Seafloor spreading gradually pushes tectonic plates apart at mid-ocean ridges.
When this happens, the opposite edge of these plates push against other tectonic plates. Subduction occurs when two tectonic plates meet and one moves underneath the other Fig. Oceanic crust is primarily composed of basalt, which makes it slightly denser than continental crust, which is composed primarily of granite. Because it is denser, when oceanic crust and continental crust meet, the oceanic crust slides below the continental crust.
This collision of oceanic crust on one plate with the continental crust of a second plate can result in the formation of volcanoes Fig. As the oceanic crust enters the mantle, pressure breaks the crustal rock, heat from friction melts it, and a pool of magma develops. This thick magma, called andesite lava, consists of a mixture of basalt from the oceanic crust and granite from the continental crust. Forced by tremendous pressure, it eventually flows along weaker crustal channels toward the surface.
The magma periodically breaks through the crust to form great, violently explosive composite volcanoes —steep-sided, cone-shaped mountains like those in the Andes at the margin of the South American Plate Fig. Continental collision occurs when two plates carrying continents collide.
Because continental crusts are composed of the same low-density material, one does not sink under the other. During collision, the crust moves upward, and the crustal material folds, buckles, and breaks Fig. The Himalayan Mountains were formed by the collision between Indian and Eurasian tectonic plates. Ocean trenches are steep depressions in the seafloor formed at subduction zones where one plate moves downward beneath another Fig. These trenches are deep up to The deepest ocean trench is the Mariana Trench just east of Guam.
It is located at the subduction zone where the Pacific plate plunges underneath the edge of the Filipino plate. How far can seismic waves reach? Why do P-waves travel faster than S-waves? Why is the interior of the Earth hot? What is the magnetic field of the Earth? Earthquakes and Faults Why do tectonic plates move? Brief history of the plate tectonics theory Before colliding with Asia, where was India? What is an earthquake? What is the highest magnitude an earthquake can reach?
What are the biggest historical earthquakes? Why do earthquakes happen in clusters? Where are earthquakes expected in the world, especially in Asia? What is a supercontinent? Are all the faults on Earth active? How can human activities cause climate change? Why do urbanisation and deforestation make flooding more likely? Earthquake Hazards Is Singapore threatened by earthquakes? Can we predict earthquakes? This causes it to sink into the mantle at subduction zones, pulling slabs of lithosphere apart at divergent boundaries and resulting in sea floor spreading or rifting.
As the lithosphere formed at divergent plate margins is hot, and less dense than the surrounding area it rises to form oceanic ridges. The newly-formed plates slide sideways off these high areas, pushing the plate in front of them resulting in a ridge-push mechanism. How plate movement operates is being revised all the time as scientists unearth new evidence, however, the detail still remains highly controversial.
We call this process subduction. The rest of the tectonic plate gets dragged along with the oceanic lithosphere, and this causes the plates to move.
Convection is another driving force behind the plate tectonics. Sometimes, these hot rocks that move to the surface can cause the crust to weaken, and new rifts and ocean basins are created. These cells were actually the reason why supercontinents were broken up throughout our history.
Tectonic plates are 62 miles thick and are made up of the continental crust and the oceanic crust. Slab pull is the most relevant force that affects the movement of tectonic plates. The heat makes the solid rocks move upwards while the colder rocks move downwards.
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