What is plate tectonic theory?

Last Update: May 30, 2022

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Plate tectonics is a scientific theory describing the large-scale motion of the plates making up Earth's lithosphere since tectonic processes began on Earth between 3.3 and 3.5 billion years ago. The model builds on the concept of continental drift, an idea developed during the first decades of the 20th century.

What is the theory of plate tectonics?

The theory of plate tectonics states that the Earth's solid outer crust, the lithosphere, is separated into plates that move over the asthenosphere, the molten upper portion of the mantle. ... Each type of plate boundary generates distinct geologic processes and landforms.

Why is plate tectonic a theory?

Plate tectonics is a scientific theory that explains how major landforms are created as a result of Earth's subterranean movements. The theory, which solidified in the 1960s, transformed the earth sciences by explaining many phenomena, including mountain building events, volcanoes, and earthquakes.

What is plate tectonics theory class 9?

Plate tectonics is the theory that Earth's outer shell is divided into several plates that glide over the mantle, the rocky inner layer above the core. The plates act like a hard and rigid shell compared to Earth's mantle. This strong outer layer is called the lithosphere.

What is a tectonic plate simple definition?

A tectonic plate (also called lithospheric plate) is a massive, irregularly shaped slab of solid rock, generally composed of both continental and oceanic lithosphere. ... Continental crust is composed of granitic rocks which are made up of relatively lightweight minerals such as quartz and feldspar.

Plate Tectonics Theory Lesson

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How tectonic plates are formed?

Continual diving of crust into mantle is sufficient to explain formation of plate boundaries. ... The plates — interlocking slabs of crust that float on Earth's viscous upper mantle — were created by a process similar to the subduction seen today when one plate dives below another, the report says.

How many tectonic plates are there?

how many tectonic plates are there? There are major, minor and micro tectonic plates. There are seven major plates: African, Antarctic, Eurasian, Indo-Australian, North American, Pacific and South American.

What are the 3 theories of plate tectonics?

The three types of plate boundaries are divergent, convergent, and transform. They are described in the following three concepts. Most geological activity takes place at plate boundaries.

What are the three types of tectonic plates Class 9?

Tectonic Plates and Plate Boundaries
  • There are three main types of plate boundaries:
  • Convergent boundaries: where two plates are colliding.
  • Divergent boundaries – where two plates are moving apart.
  • Transform boundaries – where plates slide passed each other.


Who gave the theory of plate tectonics?

Alfred Wegener in Greenland. Plate tectonics is the theory that Earth's land masses are in constant motion. The realization that Earth's land masses move was first proposed by Alfred Wegener, which he called continental drift.

What are the basic assumptions of the plate tectonic theory?

Plate tectonic theory is based on several assumptions about tectonic processes: 1) that new material is generated by sea-floor spreading at the mid-ocean ridges, which once formed become part of a plate, 2) that surface area is conserved, therefore plate material must be destroyed through another process, and 3) motion ...

What are the 3 causes of plate movement?

Mantle dynamics, gravity, and Earth's rotation taken altogether causes the plate movements. However, convectional currents are the general thought for the motion.

How do plate tectonics affect humans?

Plate tectonics affects humans in several important ways. What would Earth be like without plate tectonics? We'd have many fewer earthquakes and much less volcanism, fewer mountains, and probably no deep-sea trenches. ... In other words, the Earth would be a much different place.


What are the 2 theories behind why tectonic plates move?

Why do plates move? One explanation for plate movements is slab pull. Plates are extremely heavy so gravity acts upon them, pulling them apart. Alternatively, as shown in the diagram, convection currents under the Earth's crust transfer heat, which rises through the surface and cools back down in a circular motion.

What are the 4 types of plate tectonics?

What are the major plate tectonic boundaries?
  • Divergent: extensional; the plates move apart. Spreading ridges, basin-range.
  • Convergent: compressional; plates move toward each other. Includes: Subduction zones and mountain building.
  • Transform: shearing; plates slide past each other. Strike-slip motion.

What is the difference between plate tectonics and tectonic plates?

Tectonic plates are pieces of Earth's crust and uppermost mantle, together referred to as the lithosphere. ... Whereas Plate tectonics is a scientific theory describing the large-scale motion of seven large plates and the movements of a larger number of smaller plates of the Earth's lithosphere.

What are the two main types of tectonic plates?

The two types of tectonic plates are continental and oceanic tectonic plates.


What are the two major tectonic plates?

There are two main types of tectonic plates: oceanic and continental.

How fast do tectonic plates move?

They can move at rates of up to four inches (10 centimeters) per year, but most move much slower than that. Different parts of a plate move at different speeds. The plates move in different directions, colliding, moving away from, and sliding past one another. Most plates are made of both oceanic and continental crust.

What happens when tectonic plates move?

When the plates move they collide or spread apart allowing the very hot molten material called lava to escape from the mantle. When collisions occur they produce mountains, deep underwater valleys called trenches, and volcanoes. ... The Earth is producing "new" crust where two plates are diverging or spreading apart.

What causes the Earth's tectonic plates to move?

The heat from radioactive processes within the planet's interior causes the plates to move, sometimes toward and sometimes away from each other. This movement is called plate motion, or tectonic shift.


Which plate do we live on?

We live on a layer of Earth known as the lithosphere which is a collection of rigid slabs that are shifting and sliding into each other. These slabs are called tectonic plates and fit together like pieces to a puzzle.

How thick are tectonic plates?

Plates are on average 125km thick, reaching maximum thickness below mountain ranges. Oceanic plates (50-100km) are thinner than the continental plates (up to 200km) and even thinner at the ocean ridges where the temperatures are higher.

How are tectonic plates destroyed?

Magma rises into and through the other plate, solidifying into granite, the rock that makes up the continents. Thus, at convergent boundaries, continental crust is created and oceanic crust is destroyed. Two plates sliding past each other forms a transform plate boundary.

Can we see tectonic plates?

Iceland sits on the Eurasian and North American tectonic plates. It is the only place in the world where you can see those two tectonic plates and the Mid-Atlantic Ridge above ground.