Plate tectonics - Booklet 1 Flashcards
What are the 4 types of plate boundaries
1- Constructive (divergent) (move apart)
2- Destructive (convergent) (smash)
3- Transform (conservative) (slide past)
4- Collision (continent to continent)
What are 2 examples of intra-plates
Mount nyragongo and Hawaii
Describe the earth’s internal structure
LAMOE (lithosphere, asthenosphere, mantle, outer and inner core)
Explain how convection currents cause tectonic movement
Radio-active decay (thermonuclear fission) generates hear which causes the asthenosphere to behave in a semi-molten manner; thus allowing less dense material to rise upwards to the lithosphere where it causes frictional drag.
How did Alfred Wegener contribute the development for the tectonic theory
In 1912, Alfred used evidence to suggest that a super continent existed 250 million years ago called Pangaea; The first piece of evidence Alfred used was fossil correlation, remains of the small legged reptile (mesosaurus) were found on the coast of SE Brazil and the coast of west Africa..
Mountain correlation: Alfred suggested that the mountain ranges in Europe would have been connected to the ones in NA
Coal is a by product of plants being compressed under mass amounts of pressure, coal remains have been found in Antartica (where plants can’t grow)
Explain what happens at an oceanic plate when it meets a continental and what features are left behind
- The oceanic plate undergoes a process known as subduction, where it is being forced under a continental plate; leaving behind ocean trenches.
- The continental crust gets buckled and uplifted, leading to the formation of fold mountain chains
- As the oceanic plate sinks, it experiences mass amounts of pressure in the form of friction; which causes faulting and fracturing, ultimately leading to a huge amount of energy released.
What happens when two oceanic plates meet
The slightly denser one will subduct under the other, creating an ocean trench; as the descendant plate melts and releases magma that rises up to the surface, chains of volcanic islands form
Explain what happens at a divergent plate and what features are left behind
Plates move apart due to the rising magma in the asthenosphere, this leads to the plate to either split apart or thin; creating rift valleys
What are the land forms associated with mid ocean ridges
- Transform faults
- Pillow lavas
- Volcanic islands
- Hydro thermal vents
Explain the formation of pillow lavas
When molten lava makes its way up to the sea floor, it quickly is cooled by the sea water, crust is formed around the lump; pressure builds up until lava breaks through the new crust and the process repeats
What are the 2 main types of seismic waves (compare them)
P and S waves
- P is faster
- P can move through solid rocks and fluids
- P is least damaging
What are some primary effects of an earthquake
Mass energy release, which results in crustal fracturing and ground shaking.
Aftershocks occur after the earth read-adjusts the fault line
Define liquefaction
Is aka the main secondary effect of earthquakes, this process takes place when waterlogged/saturated sediment near the surface loses its strength in response to strong ground shaking
Identity and compare the 2 types of lava that can be possibly emitted from a volcano
- Basaltic (effusive i.e thin and runny) and Andesitic (explosive i.e slow and viscous)
- Temperature: B=1000~1200C / A=800~1000C
- Main minerals: low silica (50%) vs intermediate (60%)
- Gas content: B= 0.5~2% (low) / A= 3~4%
- Basaltic is very dangerous because it can travel considerable distance and at very high speeds
Define pyroclastic flows
Is high density mix of hot lava block and gas, rising up to extreme temperatures (700C) and travel down a volcano at very high speeds (80KM/h)
