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The Theory of Plate Tectonics - Coggle Diagram
The Theory of Plate Tectonics
Key Concepts/Essential Questions
What is the theory of plate tectonics? The theory of plate tectonics states that Earth's surface is made of rigid slabs of rock, or plates, that move with respect to each other.This theory suggested that Earth's surface is divided into large plates of rigid rock.
What are the three types of plate boundaries? The three types of plate boundaries are Divergent Plate boundaries, Transform Plate boundaries, and Convergent Plate boundaries.
Why do tectonic plates move? Tectonic plates move because the heat from radioactive processes within the planet's interior causes the plates to move.
Vocabulary
Plate Tectonics: A theory that states that Earth's surface is made of rigid slabs of plates that move with respect to each other.
Lithosphere: The cold and rigid outermost rock layer.
Divergent plate boundary: Forms where two plates separate.
Transform plate boundary: Forms where two plates slide past eachother.
Convergent plate boundary: Form where two plates collide.
Subduction: The process in which the denser plate sinks below the more buoyant plate.
Convection: The circulation of material caused by differences in temperature and density.
Ridge push: A force which results when magma rises at a mid-ocean ridge and pushes oceanic plates in two different directions away from the ridge.
Slab pull: A force that causes a dense oceanic plate to sink beneath a more buoyant plate along a subduction zone, pulling the rest of the plate that trails behind it.
Theory
The theory of plate tectonics which was proposed in the late 1960's states that Earth's surface is made of rigid slabs of rock, or plates, that move with respect to each other.
This theory suggested that Earth's surface is divided into large plates of rigid rock. Each plate moves over Earth's hot and semi-plastic mantle.
Geologists use the word tectonic to describe the forces that shape Earth's surface and the rock structures that form as a result.
The pacific plate is the largest plate, and the Juan de Fuca is one of the smallest.
Earth's tectonic plates are large pieces of lithosphere.
The asthenosphere enables Earth's plate to move because the hotter, plastic mantle material beneath them can flow.
Plate Boundaries
Types of Plate Boundaries
Transform Plate Boundaries: Forms where two plates slide past each other, and a fault system is produced. This system can result in a rapid release of energy as earthquakes.
Example: San Andreas Fault
Convergent Plate Boundaries: Form where two plates collide.The denser the plate sinks below the more buoyant plate in a process called subduction. When an oceanic plate and a continental plate collide, the denser the oceanic plate subducts under the edge of the continent. When two continental plates collide, neither plate is subducted, and mountains such as Himalayas in souther Asia form from uplifted rock.
Divergent Plate Boundaries: Forms where two plates separate, and they are most common in mid-ocean ridges. When the sea floor spreads at a mid-ocean ridge , lava erupts, cools, and forms new oceanic crust.
Example: Mid Atlantic Ridge
There are 3 main types of plate boundaries; Divergent, Transform, and Convergent.
Evidence for Plate Tectonics
Continents move apart or come together at speeds of a few centimeters per year (length of a small paperclip).
In the past, the technology used to measure how fast the continents move was not available, but now it is.
A network of satellites called the Global Positioning System (GPS) orbiting Earth, monitors plate motion.
By keeping track of the distance between these satellites and Earth, it is possible to locate and determine how fast a tectonic plate moves.
This theory also provides an explanation for why earthquakes and volcanoes in certain places.
When plates separate, collide, or slide past each other rapidly along a plate boundary it can result in earthquakes.
Volcanoes form where plates separate along a mid-ocean ridge or a continental rift or collide along a subduction zone.
Mountains can form where two continents collide.
Plate Motion
Plate tectonic activity is related to convection in the mantle, as the the lithospheric plates move over the asthenosphere.
Forces that cause Plate Motion:
Basal Drag: Convection currents in the mantle produce a force that causes motion called basal drag. Convection currents in the asthenosphere circulate and drag the lithosphere.
Ridge Push: Rising mantle material at mid-ocean ridges creates the potential for plates to move away from the ridge with a force called ridge push. Ridge push moves lithosphere in opposite directions away from the mid-ocean ridge.
Slab Pull: When tectonic plates collide, the denser plate will sink into the mantle along a subduction zone. This plate is called a slab. As a slab sinks, it pulls on the rest of the plate with a force called slab pull.
However, scientists are still uncertain about which force has the greatest influence on plate motion.
A Theory in Progress
Plate tectonics has become the unifying theory of geology as it explains the connection between continetal drift, the occurrence of earthquakes, volcanoes, mountains, and the formation and destruction of crust along plate boundaries.
However the theory of Wegener is still being revised, and several unanswered questions remain.
Questions Unanswered:
Why is Earth the only planet in the solar system that has plate tectonic activity?
Why do some earthquakes and volcanoes occur far away from plate boundaries?
What forces dominates plate motion?
What will scientists investigate next?