Plate tectonics

Question 1

Crust

Plate tectonics

Answer 1

0-70km thick and has the coolest/least dense rocks. Divided into two types:

1) continental crust- old, permanent and less dense. 10-70km thick
2) oceanic crust- younger, created and destroyed 6-10km thick and denser than continental

Question 2

Mantle

Plate tectonics

Answer 2

2,900km thick
Most of mantle (asthenosphere) is semi molten containing oxygen and silicon. Temperatures reach 5000C and create convection currents

Question 3

Core

Plate tectonics

Answer 3

Hottest part with temperatures exceeding 5000C
Outer part- liquid
Inner part- solid made from iron and nickel

Question 4

Mohorovicic boundary (MOHO)
(Plate tectonics)

Answer 4

It is a marked discontinuity which separates the crust and mantle

Question 5

Lithosphere and asthenosphere

Plate tectonics

Answer 5

Lithosphere is the crust and part of the mantle which float on soft material known as asthenosphere

Question 6

Heat in the core- primordial heat

Plate tectonics

Answer 6

This was left over form the earths formation

Question 7

Heat in the core- radiogenic heat

Plate tectonics

Answer 7

This is produced by the radioactive decay of isotopes e.g uranium -238

Question 8

Plate tectonic theory pt 1

Early earths crust/ super continent

Answer 8

Earths outer shell has over 16 plates and is constantly in motion. Movement is only few cm per year, but after moving continuously for hundreds of millions of years today’s world looks a lot different. 300 mil years ago scientists believe there was a ‘super-continent’ named Pangaea

Question 9

Plate tectonic theory pt 2

Francis Bacon and Alfred Wegener

Answer 9

Francis bacon was one of the first to recognise that continents could be fitted together, to form a single super continent. In 20th century the idea developed into process of continental drift.
Alfred wegener realised that the continents of the world fitted together like a jigsaw puzzle and Pangaea broke up and drifted apart

Question 10

Plate tectonic theory pt 3

Evidence

Answer 10

Breaking up of the super continent lead to the continents of the world and there is numerous evidence to support this theory:

1) rare fossils found in rocks 1000’s km apart
2) glaciations which affected different areas become contiguous if they are fitted back together
3) mountain ranges and foot belts are all consistent within this reconstructed super continents

Question 11

Plate tectonic theory pt 4

Magnetic orientation

Answer 11

As volcanic rock cools, it adopts magnetic orientation, which reflects that of the earths magnetic field. At times the field reverses so rocks formed at different times show opposite magnetic orientations. Taking a transact across the sea floor, geologists found that iron in the rock aligns, also that the floor was formed at different times and that the patterns either side of the mid Atlantic ridge are identical

Question 12

Plate tectonic theory pt 5

Answer 12

Rocks relating to each magnet phase could be traced linearly along the ocean floor, like a band parallel to mid ocean ridge. Comparisons of the sequences on the land and ocean floor enable rocks either side of the ridge to be measured and dared. It was found that further away from the ridge the older they are. As crust at ridge spilt and the ocean floor moves apart, new rocks are being created in the gap