How Do Convection Currents Help Form Underwater Mountains

Earth’s Tectonic Plates

USGS)

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The world’southward crust is broken into separate pieces chosen
tectonic plates
(Fig. 7.14). Recall that the chaff is the solid, rocky, outer vanquish of the planet. It is composed of two distinctly different types of material: the less-dense continental crust and the more-dense oceanic chaff. Both types of crust balance atop solid, upper mantle material. The upper mantle, in turn, floats on a denser layer of lower mantle that is much similar thick molten tar.

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Each tectonic plate is complimentary-floating and can move independently. Earthquakes and volcanoes are the direct result of the movement of tectonic plates at error lines. The term
fault is used to describe the boundary betwixt tectonic plates. Near of the earthquakes and volcanoes around the Pacific bounding main basin—a pattern known as the “ring of fire”—are due to the movement of tectonic plates in this region. Other observable results of brusque-term plate motion include the gradual widening of the Not bad Rift lakes in eastern Africa and the rising of the Himalayan Mountain range. The movement of plates can be described in 4 general patterns:

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World’s solid crust acts as a rut insulator for the hot interior of the planet.
Magma
is the molten rock below the crust, in the mantle. Tremendous heat and force per unit area within the earth cause the hot magma to flow in convection currents. These currents cause the motility of the tectonic plates that make upwards the earth’s chaff.

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The globe has changed in many ways since it first formed 4.v billion years ago. The locations of World’s major landmasses today are very different from their locations in the past (Fig. seven.18). They accept gradually moved over the form of hundreds of millions of years—alternately combining into supercontinents and pulling autonomously in a process known as
continental drift. The supercontinent of Pangaea formed as the landmasses gradually combined roughly between 300 and 100 mya. The planet’s landmasses somewhen moved to their current positions and will proceed to move into the future.

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Plate tectonics
is the scientific theory explaining the movement of the earth’s chaff. It is widely accepted by scientists today. Recall that both continental landmasses and the body of water floor are part of the earth’s crust, and that the crust is broken into individual pieces chosen tectonic plates (Fig. seven.14). The move of these tectonic plates is likely caused by convection currents in the molten rock in Earth’southward drapery below the chaff. Earthquakes and volcanoes are the short-term results of this tectonic movement. The long-term result of plate tectonics is the movement of entire continents over millions of years (Fig. 7.18). The presence of the same blazon of fossils on continents that are now widely separated is testify that continents take moved over geological history.

Evidence for the Movement of Continents

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Prove for continental drift is likewise plant in the types of rocks on continents. There are belts of rock in Africa and South America that friction match when the ends of the continents are joined. Mountains of comparable age and structure are found in the northeastern part of North America (Appalachian Mountains) and across the British Isles into Norway (Caledonian Mountains). These landmasses tin be reassembled so that the mountains form a continuous concatenation.

Paleoclimatologists (paleo
= ancient;
climate
= long term temperature and weather patterns) study prove of prehistoric climates. Evidence from glacial striations in rocks, the deep grooves in the land left past the motion of glaciers, shows that 300 mya in that location were large sheets of ice covering parts of Southward America, Africa, India, and Australia. These striations indicate that the direction of glacial move in Africa was toward the Atlantic body of water basin and in South America was from the Atlantic ocean basin. This evidence suggests that South America and Africa were once connected, and that glaciers moved across Africa and Due south America. There is no glacial show for continental movement in Due north America, because there was no ice covering the continent 300 million years ago. North America may have been nearer the equator where warm temperatures prevented ice canvas formation.

Seafloor Spreading at Mid-Ocean Ridges

Convection currents drive the movement of Earth’southward rigid tectonic plates in the planet’due south fluid molten mantle. In places where convection currents rise up towards the crust’due south surface, tectonic plates movement away from each other in a process known as
seafloor spreading
(Fig. 7.21). Hot magma rises to the crust’southward surface, cracks develop in the ocean floor, and the magma pushes up and out to form mid-ocean ridges.
Mid-ocean ridges
or spreading centers are error lines where two tectonic plates are moving away from each other.

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Mid-bounding main ridges are the largest continuous geological features on Earth. They are tens of thousands of kilometers long, running through and connecting near 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. 7.22).