1.2a drift theory

Question 1

What is Plate Tectonics

Answer 1

Refers to a set of concepts and theories explaining formation and distribution of Earth’s major structural features, seismic and volcanic events

Question 2

What Helps to Explain Plate Tectonics

Answer 2

1. Continental drift
2. Sea-floor spreading
3. Paleo-magnetism
4. Convection currents and other
   movement processes

Question 3

Earth’s Structure

Answer 3

Crust

Lithosphere

Asthenosphere

Mantle

Outer Core

Inner Core

Question 4

Crust Structure and Composition

Answer 4

approx.0-100km thick

200-400*C

Question 5

Lithosphere Structure and Composition

Answer 5

Part of crust and uppermost solid mantle

Question 6

Asthenosphere Structure and Composition

Answer 6

Part of lower crust and upper liquid plastic mantle

Question 7

Mantle Structure and Composition

Answer 7

Made from silicon and oxygen

approx.3,000km

1000-5000*C

Question 8

Outer Core Structure and Composition

Answer 8

Liquid iron and nickel

approx.5,000km

4000-6000*C

Question 9

Inner Core Structure and Composition

Answer 9

Solid iron and nickel

approx.6000km

6000C-7000C

Question 10

Continental Drift Theory Origins

Answer 10

Alfred Wegener: German geophysicist.

1912 published ‘The Origin of Continents andOceans’, which outlined his theory ofContinental Drift.

Approximately 300million years ago single continent existed which he named Pangaea.

Question 11

Continental Drift Theory Evidence

Answer 11

1. Geological evidence
   Appalachian mountains in north-east USA geologically related to Caledonian mountains of north-west Scotland
2. Biological evidence
   remains of the reptile Mesosaurus being found in southern Africa and South America – It would not have evolved identically in two different locations

Question 12

Problem with Continental Drift Theory

Answer 12

Does explain how continents drift

Question 14

Sea Floor Spreading Theory Evidence

Answer 14

Studied age of rocks on Atlantic seabed finding youngest in the middle of ocean in Iceland and oldest nearest USA and Europe.

Evidence Atlantic sea floor was spreading outwards from centre at approximately 5cm a year.

Question 15

Sea Floor Spreading Theory Origins

Answer 15

1962,
Harry Hess, US geologist, outlined theory that could explain how continents could drift. This theory later became known as ‘Sea Floor Spreading’.

Question 16

What is Palaeomagnetism

Answer 16

study of the history of changes in Earth’s magnetic field (polarity).

Every 400,000 years or so the Earth’s magnetic field switches polarity causing magnetic north and south poles to switch.

Question 17

Palaeomagnetism Evidence

Answer 17

when material from mantle rises up through ocean ridges it cools

preserves record of Earth’s magnetic field as magnetic iron in basaltic lava aligned with north pole when it cools.

when polarity switches, so too will the lava’s orientation.

Backs up Hess Sea Floor Spreading Theory

Question 18

Convection Currents in the Mantle Origin and Evidence

Answer 18

mantle is heated from hot spots in earth’s core created by increased radioactive decay

powerful enough to cause a frictional drag on earth’s lithosphere so plates move very slowly over geologic time spans.