Plate tectonics revolutionized the field of geology, which is the theory that pieces of Earth’s lithosphere, called plates, moves about slowly on top of the atmosphere.Theory of the plate tectonics explain the formation and movement of Earth’s plates.
The Mid-Ocean Ridge
A chain of underwater mountains are called mid-ocean ridge. It forms the world's longest mountain chain.
Scientists discovered a deep valley running the length of its crest and that the rocks of the ocean floor were youngest near the mid-ocean ridge.
Formation of Oceanic Crust
Sea-floor spreading is the process by which new oceanic crust is created at mid - ocean ridge as older crust moves away. Mid - ocean ridge is a huge crack in the crust where magma is pulled upward. As they move, magma from the mantle wells up and solidifies to form new oceanic crust.
Plate Boundaries
There dozen major tectonic plates on the earth. Most major plates contain both continental and oceanic crust.
There are 3 types of plate boundaries - divergent boundaries, convergent boundaries, and transform boundaries and each move in a different way. As the plates move apart, collide, or slide past each other, they cause changes in the Earth’s surface.
Plates are moving 0.1 ~ 10 centimetres per year measured by GPS.
The Mid-Ocean Ridge
A chain of underwater mountains are called mid-ocean ridge. It forms the world's longest mountain chain.
Scientists discovered a deep valley running the length of its crest and that the rocks of the ocean floor were youngest near the mid-ocean ridge.
Formation of Oceanic Crust
Sea-floor spreading is the process by which new oceanic crust is created at mid - ocean ridge as older crust moves away. Mid - ocean ridge is a huge crack in the crust where magma is pulled upward. As they move, magma from the mantle wells up and solidifies to form new oceanic crust.
Plate Boundaries
There dozen major tectonic plates on the earth. Most major plates contain both continental and oceanic crust.
There are 3 types of plate boundaries - divergent boundaries, convergent boundaries, and transform boundaries and each move in a different way. As the plates move apart, collide, or slide past each other, they cause changes in the Earth’s surface.
Plates are moving 0.1 ~ 10 centimetres per year measured by GPS.
Continental drift
Continental Drift
Process of plate tectonics were not fully understood until 1960. The early explorers began to discover the shapes of the continents, mapmakers noticed how well the shapes of North and South America fit together with Europe and Africa. Later on, geologists discovered fossils of species of land-based plants and animals on continents separated by large oceans.
In 1912 a German scientist, Wegener hypothesized that the continents were once joined in a single supercontinent, which the broke into pieces that moved part. Wegener called this ancient supercontinent, Pangaea which means “all land”. According to Wegener’s hypothesis the continents move slowly across Earth’s surface in process called continental drift.This explains why the continents seem to fit together.
Process of plate tectonics were not fully understood until 1960. The early explorers began to discover the shapes of the continents, mapmakers noticed how well the shapes of North and South America fit together with Europe and Africa. Later on, geologists discovered fossils of species of land-based plants and animals on continents separated by large oceans.
In 1912 a German scientist, Wegener hypothesized that the continents were once joined in a single supercontinent, which the broke into pieces that moved part. Wegener called this ancient supercontinent, Pangaea which means “all land”. According to Wegener’s hypothesis the continents move slowly across Earth’s surface in process called continental drift.This explains why the continents seem to fit together.
Subduction of Oceanic Plates
When Sea-floor spreading occurs, old oceanic plates sink into mate in the process of subduction. Subduction occurs near the edges of oceanic plates in regions called subduction zones. Plate sinks through a subduction zone, it bends forming a depression in the ocean floor called trench. Subduction occurs because as an oceanic plate moves away from the mid-ocean ridge, it gradually cools and becomes more dense which the gravity pulls the dense edges into the mantle, destroying the ocean floor.
Sea - flooring spreading and subduction together act like a giant conveyor belt. Sea-floor spreading creates new oceanic crust at mid-ocean ridges. Subduction destroys old oceanic crust at subduction zones. Over time, these processes change the size and shape of oceans.
Evidence for Sea-floor Spreading
Scientist found patterns of parallel magnetic “stripes” that were identical on the two side. Stripes exist because the earth’s magnetic field had reversed itself many times and caused rock crystals to line up in a certain way before the rock fully solidified. The stripes showed that new ocean floor was being added to both sides of the mid-ocean ridge at the same rate.
The Theory of Plate Tectonics
The evidence of sea - flooring spreading provided what was missing from Wegener’s hypothesis, the way for the pieces of crust moves.
According to the theory the Earth’s plates are constantly moving, each with different rate and direction.
Convection currents form in the mantle as hot rock rises at mid-ocean ridge, cools and spreads out horizontally as ocean lithosphere, and then sinks back into the mantle at subduction zones. Plate motions are visible part of the process of mantle convection. The heat that drives convection in the mantle comes from 2 sources. One is from the gradual cooling of the interior and other is from the decay of radioactive isotopes that are distributed throughout the mantle.
When Sea-floor spreading occurs, old oceanic plates sink into mate in the process of subduction. Subduction occurs near the edges of oceanic plates in regions called subduction zones. Plate sinks through a subduction zone, it bends forming a depression in the ocean floor called trench. Subduction occurs because as an oceanic plate moves away from the mid-ocean ridge, it gradually cools and becomes more dense which the gravity pulls the dense edges into the mantle, destroying the ocean floor.
Sea - flooring spreading and subduction together act like a giant conveyor belt. Sea-floor spreading creates new oceanic crust at mid-ocean ridges. Subduction destroys old oceanic crust at subduction zones. Over time, these processes change the size and shape of oceans.
Evidence for Sea-floor Spreading
Scientist found patterns of parallel magnetic “stripes” that were identical on the two side. Stripes exist because the earth’s magnetic field had reversed itself many times and caused rock crystals to line up in a certain way before the rock fully solidified. The stripes showed that new ocean floor was being added to both sides of the mid-ocean ridge at the same rate.
The Theory of Plate Tectonics
The evidence of sea - flooring spreading provided what was missing from Wegener’s hypothesis, the way for the pieces of crust moves.
According to the theory the Earth’s plates are constantly moving, each with different rate and direction.
Convection currents form in the mantle as hot rock rises at mid-ocean ridge, cools and spreads out horizontally as ocean lithosphere, and then sinks back into the mantle at subduction zones. Plate motions are visible part of the process of mantle convection. The heat that drives convection in the mantle comes from 2 sources. One is from the gradual cooling of the interior and other is from the decay of radioactive isotopes that are distributed throughout the mantle.
Divergent boundary
Plate moves away from each other along divergent boundary. When plates move apart, magma rises from the mantle to fill the gap and cools to form new rock at the edge of the plate.
Convergent boundary
Plates come together or collide at convergent boundary. When oceanic crusts slides under the less dense continental crust, the denser oceanic crust slides under the less dense continental crust.
Transform boundary
In a Transform boundary, plates slide past each other moving opposite direction.
Mountain Building
Geologist found that most mountains form along plate boundaries and some mountains form when two plates with continental crust at their edges collide. Mountains may form when oceanic plates collide with a continental plate
Plate moves away from each other along divergent boundary. When plates move apart, magma rises from the mantle to fill the gap and cools to form new rock at the edge of the plate.
Convergent boundary
Plates come together or collide at convergent boundary. When oceanic crusts slides under the less dense continental crust, the denser oceanic crust slides under the less dense continental crust.
Transform boundary
In a Transform boundary, plates slide past each other moving opposite direction.
Mountain Building
Geologist found that most mountains form along plate boundaries and some mountains form when two plates with continental crust at their edges collide. Mountains may form when oceanic plates collide with a continental plate