Tectonics

Question 1

The crust

Answer 1

Added to by sedimentation and dead sea creatures. As no metals are involved it is able to ‘float’ on the mantle.

Question 2

Why is the core metal?

Answer 2

As the Earth cooled, denser materials like iron and nickel sank. It’s kept solid by the pressure of all the layers.

Question 3

Description of constructive margin

Answer 3

-Core heats magma, rises to asthenosphere
-Cannot break through so moves parallel
-Plates are dragged apart
-Ridge push as plates are pushed up in the middle and their weight pushes them apart
-Slab pull where the other end of the plate is on a destructive margin
-Mid Atlantic ridge

Question 4

Paleomagnetism

Answer 4

Study of magnetic rock to record history of the magnetic field

Question 5

Continental drift (pangea) and evidence for

Answer 5

Alfred Wegner 1915
-Jigsaw fit
-Geology that seems to be the same across continents
-Fossil evidence

Question 6

Crust characteristics

Answer 6

400 C
Less dense
Granite & basalt
Solid

Question 7

Mantle characteristics

Answer 7

870 C
Less to medium density
Upper=olivine Lower=magnesium silicate
Liquid & solid

Question 8

Outer core characteristics

Answer 8

4400-6100 C
Dense
Iron & sulphur
Liquid

Question 9

Inner core

Answer 9

7000 C
Very dense
Iron & Nickel
Solid

Question 10

Effusive

Answer 10

Runny

Question 11

Description of destructive margin

Answer 11

-Oceanic plate is subducted (slab pull)
-Fold mountains, as plate concertinas
-Melted rock & gas in subduction zone
-Great pressure so magma rises to make volcanoes, these are explosive
-Many shallow and deep EQs with benioff zone going deep
-Nazca and SA plates

Question 12

Description of continental collision margin

Answer 12

-Neither subducts so no volcanoes
-Crumple upwards to make fold mountains
-EQs mainly on boundary and are very violent, also intra-plate as plates deform
-The Alps (African and Eurasian)

Question 13

Description of transform margin

Answer 13

-Plates move parallel
-No subduction so no volcanoes
-Many shallow EQs
-Elastic rebound
-San Andreas Fault

Question 14

Elastic rebound

Answer 14

Plates get stuck at the margin so start to bend. Snap back to original shape in new locations.

Question 15

Formation of island chains

Answer 15

-Hotspot in oceanic plate
-Outpouring of basalt makes land
-Plate moves so creates island in new spot
-Hawaii

Question 16

Causes of intra-plate EQs

Answer 16

-Old weaknesses from previous collisions
-Climate change causing isostatic rebound
(New Madrid fault line)
-Rising sea levels adding weight to crust

Question 17

Viscosity

Answer 17

Low=runny High=thick
More silica = Higher viscosity

Question 18

Basaltic lava

Answer 18

Low viscosity
Where lava is heated by core and low in gas
Low magnitude eruptions
Constructive margins

Question 19

Effusive

Answer 19

Lava runs down the volcano

Question 20

Rhyolitic lava

Answer 20

High viscosity
Where subduction adds silica, gas and water to the magma
Magma has difficulty making it to the surface but creates very explosive eruptions when it does
Ash clouds, pyroclastic flows, volcanic bombs and lahars
Destrucive margins

Question 21

Earthquakes

Answer 21

Focus- Origin point
Epicentre- Point on surface above focus
Seismic waves- Transmit energy from eq

Question 22

EQ wave types

Answer 22

P - Compression, less damaging, fastest
S - Vertical amplitude, slower
L - Side to side, most damaging, at surface

Question 23

Liquefaction

Answer 23

Water saturated material becomes loose and water surrounds all grains.
Christchurch, New Zealand

Question 24

Primary impacts of a volcano

Answer 24

Lava flow
Pyroclastic flow
Gas eruptions
Ash cloud

Question 25

Secondary impacts of a volcano

Answer 25

Lahars
Landslides
Jokulhlaup
Acid rain

Question 26

Pyroclastic flow

Answer 26

Formed from collapse of eruption column; lava dome or lava flow. Fluidized by water vapour and gases. Montserrat 1997

Question 27

Lahar

Answer 27

A slurry of mud, water and volcanic debris, formed when a pyroclastic flow melts snow/ice or there is heavy rainfall.