Why Are Some Locations More At Risk From Tectonic Hazards

Question 1

Divergent/ constructive plate boundary

Answer 1

Oceanic oceanic plates move apart due to slab pull, where the weight of 1 end of the plate is pulled by gravity into the earth’s mantle which causes magma to rise which eventually leads to the formation of a mid-ocean ridge. Sea floor spreading where the new crust pushes the older crust away from the ridge continuously expands the ocean basin

Magma is basaltic, less viscus
VEI-is lower but volcanic eruptions are effusive
Runnier lava creates shield/flat volcanoes

Question 2

Convergent/destructive

Answer 2

Slab pull is forcing the subduction of the oceanic plate which is denser and heavier underneath continental plate, heat from the magma,friction and pressure from the plates can build up in the Benioff zone forming fold mountains e.g. Andes mt. Lava is andestic, more viscus

VEI= is higher but less frequent
Earthquakes are larger on moment magnitude scale

Question 3

Convergent-collision

Answer 3

2 continental plates.g. Indian subcontinent plate and Eurasian plate form fold mountains like the Alps and Himalayans , little magma as the 2 plates are pushing upwards rather than being subducted

EQ= large powerfulhard to predict

Question 4

Conservative -transform

Answer 4

Oceanic and continental as they move alongside at different speeds forming fault lines e.g. Andreas fault line
EQ=large

Question 5

Hotspots formation

Answer 5

Mantle plum underneath the crust of the earth form large magma chambers as the plates move over them which leads to chains of volcanic islands e.g. Hawaii

Question 6

Intraplate EQ

Answer 6

Found at quite a distance from plate boundaries. Occurs at old fault lines which have now moved away because they are no longer on a plate boundary. The faults r reactivated by contemporary stress e.g. the new Madrid seismic zone

Question 7

How do we know that these plates move?

Answer 7

It is originally thought that convection currents by heat in earths core and mantle magma lead to pate sat above the magma being forced into different directions.
Now thought that the gravity is leading to slab pull, subduction and lead to sea floor spreading which is backed by paleomagnetism, where the magnetic field changes every 400,000 yrs. according to Wagner, he found that the rocks in Greenland and the UK have the same paleomagnetusm and were once joined (Pangea)

Moreover, fossils of the mesosauras who was a freshwater reptile could not have crossed oceans, therefore all the continents were once connected as started to move away due to slab pull