Please enable JavaScript.
Coggle requires JavaScript to display documents.
The Theory of Plate Tectonics 7.3 Notes - Coggle Diagram
The Theory of Plate Tectonics 7.3 Notes
The Plate Tectonics Theory
The theory of plate tectonics was created in the 1960s.
The theory states that Earth´s surface is made of rigid slabs of rock, or plates, that move with respect to each other.
Each plate moves over Earth´s hot and semi-plastic mantle.
Plate Boundaries
Divergent Plate Boundaries
Forms where two plates separate.
They pull continents apart and form rift valleys.
An example is the the East African Rift.
Transform Plate Boundaries
Forms when two plates slide past each other.
Earthquakes are caused by this type of plate boundary as the stress that builds up from where the plates get stuck becomes too great and the rocks break.
An example is the San Andreas Fault in California.
Convergent Plate Boundaries
Forms when two plates collide. The denser plate sinks below the more buoyant plate in a process called subduction.
When an oceanic plate and a continental plate collide a deep ocean trench is formed.
A line of volcanoes are formed when to oceanic plates collide.
When 2 continental plates collide mountains are formed.
Evidence for Plate Tectonics
When the theory was first proposed the proper technology to prove it had not yet been created.
Now a days scientists use satellites called GPS to measure how fast continents move.
Plate Motion
Convection Currents
Convection currents are the circulation of material caused by differences in temperature and density.
When materials are heated they become less dense and it rises upward and comes in contact with Earth's crust. Thermal energy is transferred from the hot mantle to Earth's crust, forming a convection current.
Forces Causing Plate Motion
Basal Drag
- Convection currents in the mantle produced by a force that causes motion called basal drag.
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.
Slab Pull
- As a slab, sinks it pulls on the rest of the plate with a force called slab pull.
It is now known that continents move because the asthenosphere moves underneath the lithosphere
A Theory in Progress
The investigation that Wegener began nearly a century ago is still being revised.
Unanswered questions:
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 dominate plate motion?
What will scientists investigate next?
Tectonic Plates
There are seven major plates.
The hot, plastic texture of the lithosphere is what allows the Earth's plates to move.
The Pacific Plate is the largest plate.
The Juan de Fuca Plate is one of the smallest plates.