Plate boundaries Flashcards
What is plate tectonics?
Theory developed to explain the large scale movements of rock in the Earth’s crust
What is the lithosphere?
Earth’s surface layer, made of the crust and upper mantle, broken into sections with an average depth of 100km
What is the asthenosphere?
The liquid part of the mantle, that allows some movement of the lithosphere
What are divergent/constructive boundaries?
Plates moving away from each other
Fresh basaltic magma rises to the surface and cools creating rock
Forms lava flows and shiel volcanoes
Can cause small earthquakes, landslides and tsunamis
Can be:
- Oceanic crust from ocean crust
- Continental crust from continental crust
What are convergent/destructive boundaries?
Plates moving towards each other
Oceanic crust is subducted below the less dense continental crust and is pushed into hot mantle and melts while also causing an ocean trench and high friction causes strong earthquakes
The subducted plate causes the magma to rise up through the crust resulting in violent composite volcanoes
Can be:
- Oceanic crust to ocean crust
- Oceanic crust to continental crust
- Continental crust to continental crust
What are conservative or transform boundaries?
Two plates slide along each other
The friction causes highly destructive earthquakes and possible landslides, tsunamis and avalanches
Can be:
- Between oceanic, continental or a mixture of plates
What is an example of a constructive/divergent boundary?
Mid Atlantic Ridge
What is an example of a destructive/convergent boundary?
Andes Mountains
What is an example of a conservative boundary?
San Andreas Fault
What is a collision zone?
Two continental crusts collide
They are of equal density so no subduction occurs
Instead they form collision zones of fold mountains
Can cause strong earthquakes, landslides and avalanches
What is an example of a collision zone?
Himalayas Mountains
What is a hotspot?
Areas of volcanic activity unrelated to tectonic activity
- Hot magma plumes from the mantle rise and burn through weaker parts of the crust forming volcanoes and islands
What is the theory of continental drift?
At one point all continents were one supercontinent called Pangea
Over time very slowly tectonic plates move in different directions creating the world we know today
What are convection currents?
Due to radioactivity in the inner core heat rises through the outer core and mantle
The semi molten rock in the mantle is heated and becomes less dense than its surroundings and rises
When this reaches the crust it spreads moving large slabs of crust
This causes tectonic movement
What are Earth’s layers (bottom to top)?
- Inner core
- Outer core
- Lower mantle
- Upper mantle (the asthenosphere)
- Lithosphere (crust and upper mantle)
- Oceanic and continental crust
What are the properties of the inner core?
A solid ball of iron because it’s under a lot of pressure of all the other layers above it, contains radioactive elements as well and is about 5200 degrees Celsius
What are the properties of the outer core?
Molten (liquid) because it’s under less pressure and is also iron. About 4500 degrees Celsius
What are the properties of the lithosphere?
Cool and brittle solid rock
What are the properties of the crust?
Crust is split into slabs (tectonic plates)
- Oceanic crust is dense and thin
- Continental crust is less dense and thick
What are the types of plate boundaries?
- Constructive/divergent
- Destructive/convergent
- Collision zone
- Conservative
Where do shield volcanoes occur?
At constructive/divergent plates and hotspots
Where do composite volcanoes occur?
Convergent/destructive plate boundaries
