Tectonics Flashcards
(39 cards)
What occurs at divergent plate boundaries?
Plates move away from each other, forming new crust as magma rises.
Causes volcanoes, earthquakes,mid ocean ridges,rift valleys
What occurs as convergent destructive plate boundaries?
Two plates (at least one oceanic) move towards each other and the denser plate is forced beneath the other plate, in subduction.
What occurs at convergent collision plate margins?
Two continental plates move towards each other and collide, which causes huge pressure.
What occurs at transform plate boundaries?
Plates slide past each other, causing enormous friction which leads to earthquakes.
Where are tectonic hazards usually located?
At plate boundaries, however there are some anomalies like Hawaii.
What is the ring of fire?
An area of high tectonic and seismic activity around the Pacific Ocean .
What is mantle convection?
When plates move due to convection currents, which is when magma moves in circles
What is slab pull?
When oceanic crust becomes denser and cools, it sinks into the mantle causing a pull on the plate.
What is the Continental Drift theory?
- created by Alfred Wegner in 1915
- stated that continents fit together like puzzle pieces and were originally joined into a supercontinent named Pangea
-His evidence was that an ice sheet had advanced from India
What is the Seafloor Spreading theory?
-created by Henry Hess in 1962
-said ocean ridges mark where magma rises, and as magma came out, the ocean floor was pushed away from each other other
What is the Paleomagnetism theory?
-created by Vine and Matthew’s in 1963
-discovered that the earths magnetic field has changes many times
-at ridges, there were patterns of rock that alternate in polarity
-this meant that the rock was created at different times
What is the Walti-Benioff Zone theory?
-created by Walti and Benioff in 1949
-the zone where oceanic plate sinks at a subduction zone
-concluded after observing earthquakes at the South American subduction zone
What is the convection current theory?
-created by Arthur Holmes in 1919
-he proposed that in the mantle, there are convection currents that reshape the earths surface
-the upward movement at convection currents may lift the earths crust
What is the contraction theory?
-created by Beaumont and Seuss in 1800s
-believed after earth formed, the surface cooled and wrinkled
-proposed that mountain ranges like the Himalayas were forced upwards by wrinkling
What are the reasons why some places suffer more from earthquakes than others?
-Earthquake magnitude
-tectonic distribution
-population density
-infrastructure vulnerability
-extent of preparations
-levels of development
-nature of bedrock
How is population density linked to earthquake suffering?
The more densely an area is populated, means more people are living there, so there will be more death and injury.
How is type of rock linked to earthquake suffering?
Some types of rock are ‘liquified’ when shaken, which causes instability of building foundations and damage to infrastructure.
How are magnitude and depth linked to earthquake suffering?
The stronger an earthquake, the more serious the damage can be. Shallow earthquakes usually cause more damage because the focus is closer to the earths surface.
How does the extent of earthquake preparedness link to earthquake suffering?
Areas that are more prepared for earthquakes like CA and Japan usually have regular drills and emergency services practise their responses. In poorer countries, less money is likely to be spent on preparation, so the damage is often much more significant.
What are the 3 types of wave?
P waves, S waves and L waves
What are P (primary) waves?
-the first type of of wave to arrive
-vibrations caused by compressions
-travel at 8km/s
What are S (secondary) waves?
-the second type of wave to hit
-only travel through solids
-shake the ground violently
What are L (love) waves?
-last type of wave
-have a high amplitude so cause significant damage
What secondary hazards do earthquakes cause?
Soil liquefaction, landslides and tsunamis
