1. The Earth and its oceans - 1.2. Plate tectonics Flashcards
What causes the crust to move?
Convection currents (caused by radioactive decay of atoms in the Earth core heating the mantle)
What are the large pieces of crust called?
Tectonic plates
What has caused the crust to break into tectonic plates?
Convection currents creating tension in the crust
What is Pangea?
A supercontinent - all continents were once joined together
What happened to Pangea?
Most of the continents have slowly drifted apart from each other over time
Name the three types of tectonic plate boundaries
divergent, convergent and transform
What is a divergent plate boundary?
When 2 tectonic plates move away from each other
What happens in the gap between the plates in a divergent plate boundary?
The magma rises and fills the gap
What is the difference between magma and lava?
Magma is the molten rock in the mantle. It is called lava once it gets to the upper surface of the crust.
What is an earthquake?
Sudden movement of tectonic plates
If molten lava is suddenly released to the surface and cools unevenly around a divergent plate boundary, what happens?
Uneven mountain ranges are formed wither side of the divergent plates
Where do most divergent boundaries occur?
In the ocean between continents
Name 3 features associated with divergent plate boundaries?
Earthquakes, volcanoes and mid-ocean ridges
How are volcanoes formed?
When plates move apart (divergent plate boundary), allowing magma to rise up and escape as lava
What is a mid-ocean ridge?
An extensive mountain range formed deep in the ocean, extending for hundreds of miles either side of parting plates (divergent plate boundary)
How are hydrothermal vents formed?
Cold sea water seeps into cracks in the sea floor and is superheated by the magma beneath
What is a convergent plate boundary?
When 2 tectonic plates move towards each other and the plates collide
What happens when both sections of converging tectonic plates are continental crust?
Fold mountains are created
Give an example of fold mountains
The Himalayan mountain range
The Alps
What happens when a section of continental crust converges with a section of oceanic crust?
The denser oceanic crust undergoes subduction - it goes underneath the continental crust
Name 4 features associated with convergent plate boundaries?
Earthquakes (sudden movement of plates),
Tsunamis (caused by earthquakes),
Volcanoes (when an oceanic plate subducts and melts)
Ocean trenches
What is a transform plate boundary?
When tension between 2 plates sliding against each other means they suddenly slip, causing an earthquake
What is a tsunami?
An extremely large volume of seawater is displaced (such as when 2 plates move suddenly)
What effect does the huge amount of energy transferred through the moving water in a tsunami wave have?
It moves rocks and sediments on the sea floor, destroying habitats
Name a natural defence against tidal action and tsunamis
Coral reefs
What are the impacts of a tsunami?
Damage to coral reefs
Damage to coastal seagrass beds and mangroves
Damage to oceanic floor habitats
Damage to human communities along the coastline
Loss of life
Impact on costal economies
Farmland flooding
