Tectonic Processes Flashcards
What are three pieces of evidence of continental drift?
- jigsaw fit
- fossil remains of freshwater reptile in South America and Africa
- Coal in Antarctica (couldn’t form there at current latitude)
explain mantle convection
radioactive decay in the inner core causes magma in lower mantle to rise into the asthenosphere. it cools and sinks in a circular motion causing a convection current.
What is paleomagnetism?
the study of the earth’s magnetic field
What is seafloor spreading?
magma is forced up from the asthenosphere, forcing apart the crust and hardens to form new crust
How does paleomagnetism prove seafloor spreading?
the change in direction of the earth’s magnetic field every 400,000 years matches the change in the direction of the minerals inside the rock (cooled lava). hence new rock formed at the same time on both sides
What is subduction and what does it prove the earth is not doing?
two plates collide, the denser subducts and melts. hence showing the earth is not expanding
What is slab pull?
crust pulls apart and subducts due to the weight of the magma
what are the two different types of waves?
Body waves and surface waves
what are body waves and what are the two types of body waves?
body waves move through the earth’s ‘body’.
- P waves
- S waves
what are surface waves and what are the two types of surface waves?
move through the surface/ crust only
- Love waves
- Rayleigh waves
what are the four characteristics of P waves?
- fastest wave
- first to reach surface
- travel through solids and liquids
- compress/ expand crust
what are the four characteristics of S waves?
- 60% speed of p waves
- travel through solids
- move crust up/ down
- more damaging than p waves
what are the three characteristics of Love waves?
- fastest surface wave
- move crust side to side
- most damaging
what are the two characteristics of Rayleigh waves?
- travel with rolling motions
2. move crust up/ down
what are the two theories to explain intraplate earthquakes?
- stress builds along ancient faults causing them to become active
- crust that was once weighted down by glaciers is slowly rebounding from mantle
what are the two primary effects of earthquakes?
- ground shaking
2. crustal fracturing
what are the four secondary effects of earthquakes?
- Tsunami
- Liquefaction
- Fire
- Landslide/ avalanches
what are the four primary effects of volcanoes?
- lava flows
- pyroclastic flow
- tephra
- gas eruptions
what are the two secondary effects of volcanoes?
- Jokulhlaup
2. Lahars
explain effects of ground shaking
infrastructure collapse, killing/ injuring those nearby
explain effects of crustal fracturing?
crust cracks at surface
explain liquefaction
surface rocks lose strength and become more like liquid. the ground loses the ability to support weight
explain how earthquakes cause a fire
underground power/ gas pipes are severed
explain how earthquakes cause landslides or avalanches
shaking puts pressure on slopes causing them to fail
what is lava flow?
liquid rock expelled from the crown or flank of a volcano
what is pyroclastic flow?
dense masses of gases and lava fragments flow down the sides at high speed
explain jokulhlaup
water/ ices released from a glacier by heat from lava
what are lahars
volcanic mudflow caused when ash mixes with some kind of water
what is tephra?
the ash which is projected to a great height, falling to cover land and property
what are gas eruptions?
poisonous sulphur dioxide/ monoxide released before, during and after eruptions. CO2 and water vapour are the most common gases coming from a volcano.
Explain how Tsuanmis forms
- displacement of a large area of the sea floor caused by uplift fault blocks or crust rebounding causes a water column to rise
- the wave radiates in all directions from the source
- as the water shallows the waves slow down and increase in heigh due to friction
- wave energy is crowded into a smaller volume of water
