plate tectonics

Question 1

What is the earths structure

Answer 1

Core
Mantle
Crust
Lithosphere

Question 2

What elements are in the crust

Answer 2

Silicon, oxygen, aluminium, pottasium

Question 3

How thick is the crust below the ocean

Answer 3

6-10km

Question 4

How thick is the crust below land

Answer 4

30-40km

Question 5

How thick is the lithosphere

Answer 5

60-70km

Question 6

What are the two types of crust

Answer 6

Continental and oceanic

Question 7

Which type of crust is denser

Answer 7

Oceanic

Question 8

What is the composition of continental crust

Answer 8

Mainly granite, silicon,aluminium and oxygen

Question 9

What is the composition of oceanic crust

Answer 9

Basalt, silicon,magnesium and oxygen

Question 10

How do the plates move

Answer 10

Convection currents which push and pull the plates

Question 11

What was Alfred wegeners theory of tectonic

Answer 11

That tectonic plates have evolved from pangea, 300 million years ago

Question 12

How is sea floor spreads evidenced

Answer 12

Examination of the oceanic crust either side of the mid Atlantic ridge (alternating polarity of magnetic rock)

Question 13

What create thermal convection currents

Answer 13

Hot spots in the mantle

Question 14

Biological evidence for continental drift

Answer 14

-Fossil remains of mesosaurus in Brazil and South Africa
-fossil brachiopods found in Indian limestone and Australia
-fossil remains of plant which existed when coal was being formed found in India and Antarctica (coal only forms in tropical conditions)

Question 15

Evidence for continental drift- climatology

Answer 15

Evidence of glaciation found in South America and India

Question 16

Evidence for continental drift- geology

Answer 16

Rocks of similar age,formation and structure found in Brazil and South Africa
Coal sandstone and limestone could not have been formed in Britain with its current climate

Question 17

Palaeomagnetism

Answer 17

In underwater eruptions basaltic lava cools
Rock aligns with earths magnetic field
This is reversed every 400,000 years
Bands of rock facing different poles are formed

Question 18

Constructive margins occurs where

Answer 18

Two plates move away from eachother

Question 19

What do constructive boundaries form

Answer 19

Rift valleys
Mid oceanic ridges

Question 20

Volcanic activity at constructive boundaries

Answer 20

Gentle slides
Basaltic lava
Gentle eruptions
Frequent
Effusive

Question 21

Transform faults

Answer 21

Occur at right angles to boundary as new crust is formed
Friction and earthquakes )shallow focused)

Question 22

Rift valleys

Answer 22

-form when plates move apart on continental areas
-areas of crust drop down parrallel faults
-forms an upstanding block known as a horst
-in east african rift valley it is said to be an emergent plate boundary and forming a new ocean

Question 23

Example of rift valley

Answer 23

East African rift valley
Extends for 5000km from Mozambique to the Red Sea and Jordan
Width varies from 10-50km

Question 24

Conservative plate margins occur when

Answer 24

Two plates move past eachother

Question 25

What hazards occur at conservative margins

Answer 25

Earthquakes only

Question 26

Example of conservative margin

Answer 26

San Andreas fault in california

Question 27

Destructive margins occur when

Answer 27

Two plates move towards each other and the heavier plate sinks beneath the lighter plate

Question 28

Example of destructive margin

Answer 28

Andes, west coast of South America Nazca plate subducts under South American plate Molten magma rises forming explosive volcanoes

Question 29

What are island arcs and how are they formed

Answer 29

- subducting plate becomes hot -pressure and friction melts the plate -rises to the surface as a pluton of magma -composite volcano islands are formed

Question 30

Where are fold mountains formed

Answer 30

-Destructive continental and continental boundaries -there is no subduction -edges and sediments are forced upwards -there is no volcanic activity -indo-australian plate travelling nirthwards into eurasian -formed the himalayas

Question 31

How do fold mountains form

Answer 31

Lower density continental courts collide Plate edges forced upwards No subduction so no volcanic activity e.g. the Himalayas

Question 32

Hotspots

Answer 32

Areas on the crust of volcanic activity that are not related to hazards

Question 33

What do hot magma plumes do

Answer 33

Burn through weaker parts of the crust and states in the same plates as the plate moves

Question 34

Hawaiian chain of volcanic islands facts and figures

Answer 34

60° bend in the shape of the islands 3,700 miles long Travelling NW Are getting eroded Up to 5 million years old

Question 35

What does Tuzo Wilson say creates magma plumes

Answer 35

Static radioactive elements

Question 36

What does Foulger 2003 suggest forms hotspots

Answer 36

Weakness in tectonic plates Faults in the crust allow plume of magma through

Question 37

What is a mantle plume

Answer 37

A pocket of magma which has melted through the asthenosphere from the core due to static radioactivity

Question 38

What is the most common rock type formed by the eruption of Hawaiian volcanoes

Answer 38

Basaltic rock (low silica and low gas content)

Question 39

ocean ridges

Answer 39

longest continuois uplifted features when plates move apart in oceanic areas space is filled with basaltic lava, cools and forms magnetic rock volcanic acitivity - submarine volcanoes

Question 40

deep sea trenches

Answer 40

where oceanic and continental plates move denser plate subducts nazca under south american formed peru-chile trench

Question 41

island arcs

Answer 41

during subduction the descending plate enters hotter surroundings generated by frcition begins to melt the plate material is less dense and rise towards surface as plutons of magma eventually reach surface and form compositive explosive volcanoes

Question 42

Sea floor spreading theory

Answer 42

After discovery of mid Atlantic ridge Altenratating polarity of the rocks - iron/magnetic particles in erupted lava Poles reverse every 400,000 years Results in magnetic stripes that are aligned to the poles Oceanic crust gets older with the distance from the ridge

Question 43

Ridge push / gravitational sliding

Answer 43

Constructive boundaries Upwelling of hot material at ocean ridges - creates buoyancy effect Plates experience force that acts away from the ridge Gravity acting down the slope of the ridge

Question 44

Slab pull

Answer 44

Destructive boundaries Downward gravitational force on the cold dense decending plate Pills the whole oceanic plate down as a result of negative buoyancy Frictional resistance - gives rise to shallow and deep earthquakes