Historical Geology - Plate Tectonics

Question 1

What is continental drift?

Answer 1

Continents have moved horizontally over Earth’s surface.

Question 2

Describe early evidence for continental drift.

Answer 2

• Shorelines of the continents fit together like pieces of a puzzle.
• similar fossil plants and animals occurred on widely separated land masses.
• Living animals locations.

Question 3

How many major plates are there?

Answer 3

8

Question 4

What is mantle convection (convection in the mantle)?

Answer 4

It is like the circular motion that occurs when heating a thick fluid.
The heated fluid rises to the surface, spreads out and begins to cool (oceanic crust), and then sinks back down (subducted) to the bottom of the pot (deep sea trench) where it gets reheated and rises again. This motion results in a convection cell.

Question 5

Who proposed the idea of mantle convection?

Answer 5

Harry Hess in 1962

Question 6

What is the Continental crust made of?

Answer 6

Felsic rocks (less dense than Mafic rocks). Rich in Si and Al

Question 7

What is Oceanic crust made of?

Answer 7

Mafic rocks (more dense than Felsic). Rich in Mg and Fe

Question 8

What are the three kinds of Plate tectonic Boundaries?

Answer 8

1. Divergent Plate Boundary
2. Convergent Plate Boundary
3. Transform Faults

Question 9

What are the three kinds of Plate tectonic Boundaries?

Answer 9

1. Divergent Plate Boundary - two plates pulling apart from each other eg. mid-oceanic ridge
2. Convergent Plate Boundary - where plates collide eg mountain chains
3. Transform Faults - occurs where plates slide past one another eg San Andreas Fault

Question 10

What is a fault? Name the kinds of faults and describe each.

Answer 10

Movement along a rock fracture or crack.

1. Normal fault - block above the fault drops down
2. Reverse fault - block above the fault rises
3. Strike-slip fault - slide side by side

Question 11

When is a Graben formed?

Answer 11

when a block of crust sinks between faults.

Question 12

What is the Horst?

Answer 12

The horst is the block that stays in the same place when the crust sinks.

Question 13

What is a hydrothermal vent? Where do they occur?

Answer 13

A fissure in a planet’s surface from which geothermally heated water emerge. they occur at mid-oceanic ridges and are sites of unusual ecosystems (sulphur-based) (reverse fault)

Question 14

What is a Deep Sea Trench?

Answer 14

Where a plate gets subducted beneath another plate and into the mantle.

Question 15

What is a hot spot?

Answer 15

Small localized areal of the crust with very high heat flow. Formed by a mantle plume.