Plate Tectonic

Question 1

Who put forward the theory of continental drift?

Answer 1

Alfred Wegner (pre WWII)

Question 2

What were some of the evidences in support of the continental drift theory Pre WWII?

Answer 2

Visual Observations (continental borders seemed to line up) Geographical composition seemed to match on opposite sides of the world (fossils, rocks, mountains, etc.)

Question 3

What were some of the evidences in support of the continental drift theory Post WWII?

Answer 3

Seismic technology was greatly advanced during the second world war.
If we spot location of earthquakes on the global map, over certain time interval (e.g. 5
years), it seems they form well-defined lines,

Location of earthquakes define a global pattern where the PLATES
are the pieces, not the continents!

Question 4

why is the sea floor spreading process important?

Answer 4

was a pivoting point in development
of this theory that changed the Wegner’s Continental Drift
theory to the plate tectonics theory.

Question 5

Explain the two types of crust that earth has

Answer 5

Continental Crust (Continental plate)
Very thick (10-70km)
buoyant (floats easily on Magma)

Oceanic Crust (Oceanic plate)
thin (~7 km)
dense (tends to sink)

Question 6

What is a convergent boundary?

Answer 6

Two plates pushing toward each other (–> <–)
ex. boundary between the eurasian and indian plate, causing the himalaya mountain range to form

Question 7

What is a divergent boundary?

Answer 7

Two plates pushing apart from each other (<– –>)
ex. the boundary between the african plate and arabian plate in the red sea

Question 8

What is a transform boundary?

Answer 8

Two plates sliding past one another
ex. the boundary between the pacific plate and the australian plate crossing new zealand

Question 9

Name some examples of convergent boundaries

Answer 9

1. Continental - oceanic
2. Oceanic - oceanic
3. continental - continental

Question 10

Name some examples of divergent boundaries

Answer 10

4. oceanic - oceanic
5. continental - continental
6. continental - oceanic

Question 11

Name some examples of transform boundaries

Answer 11

7. continental - continental
8. continental - oceanic
9. oceanic - oceanic

Question 12

what happens when an oceanic plate collides with a continental plate

Answer 12

oceanic goes sinks under the continental as it is heavier

Question 13

what happens when an oceanic plate collides with a oceanic plate

Answer 13

one oceanic plate sinks under and one goes over, subduction zone is still created

Question 14

what happens when an continental plate collides with a continental plate

Answer 14

no subduction process happens, instead, they collide
head-to-head and push hugely on one another for millions of years, forming highest elevated
mountainous regions

Question 15

what is a seismograph?

Answer 15

Seismographs are instruments that record seismic waves, usually
installed few kilometers below the surface of ground

Question 16

what is the difference between P and S waves

Answer 16

P-Waves: direction of wave propagation is in the same direction as compression and
expansion of the rocks.

S-Waves: direction of wave propagation is perpendicular to the direction of rocks
motion.

Question 17

which wave travels faster

Answer 17

When an earthquake happens, both P-wave and S-wave are generated at the same
time.
But P-waves travel at higher speed than S-waves (about 1.7 times faster)