The Theory Of Plate Tectonics by Kayla Donnell

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The Theory Of Plate Tectonics

Published on Nov 19, 2015

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A Canadian scientist named J. Tuzla Wilson observed cracks in the continents similar to those on the ocean floor. According to Wilson the llithosphere is broken into separate sections called plates.

Photo by Keith M Avery

Wilson combined what geologist knew about sea-floor spreading, Earth's plates, and continental drift into a single theory, a scientific theory. The theory of plate tectonics.

Photo by WorldIslandInfo.com

The theory of plate tectonics states that pieces of Earth's lithosphere are in slow, constant motion, driven by convection currents in the mantle.

Geologist think that movement of convection currents in the mantle is the major force that causes plate motion.
As the plates move, they collide, pull apart, or grind past each other.

Photo by NASA: 2Explore

Plate boundaries extend deep into the lithosphere. Faults—breaks in Earth's crust where rocks have slipped past each other—form along these boundaries. Scientists have used instruments on satellites to measure plate motion very precisely.

Photo by Miguel Vera

The place where two plates move apart, or diverge, is called a divergent boundary. Most occur along the mid-ocean ridges where sea-floor spreading occurs. They also occur on land. When it develops on land, two of Earth's plates slide apart.

A deep valley called a Rift Valley forms along the divergent boundary.

Convergent boundaries
The place where two plates come together, or converge, is called a convergent boundary. When two plates converge, the result is called a collision. Where two plates carrying oceanic crust meets at a trench, the plate that is more dense sinks under the other plate.

When two plates carrying continental crust collide, subduction does not take place. Neither piece of crust is dense enough to sink very far into the mantle. Instead the collision squeezes the crust into mighty mountain ranges.

A transform boundary is a place where two plates slip past each other, moving in opposite directions. Earthquakes often occur along transform boundaries, but crust is neither created nor destroyed.

The movement of Earth's plates has greatly changed Earth's surface. Pangea itself formed when Earth's land masses drifted together about 260'million years ago. About 225 million years ago, Pangea began to break part.

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Kayla Donnell