Tectonic

Question 1

What 2 different crusts makes up the earths crust

Answer 1

Oceanic - thinner and denser 6-10km thick;lines the ocean floor=basaltic

Continental-older,thicker 45-50km, it is less dense ; makes up the world land masses =granitic

Question 2

What is the mantle

Answer 2

Sits below the crust and is the widest layer.

The upper part is sold (lithosphere ) and the lower part is semi-molten and is split into the asthenosphere and mesosphere

Question 3

What is the outer core

Answer 3

Semi molten and consists of iron and nickel 4500-6000 degrees

Question 4

What is the inner core

Answer 4

Layer is solid and made of iron.
Its the hottest layer at 6000º

Question 5

Plate tectonic theory

MANTLE CONVECTION

Answer 5

Earths core temperature (6000º)increases due to radioactive decay
Causes hot magma to rise up towards the crust
Once it hits the crust its forced to cool and sink back down to the core
Which forms currents as they flow below the LITHOSPHERE, carrying the plates with them

However, this theory was discredited due to limited evidence of convection currents and their existence

Question 6

Plate tectonic theory
RIDGE PUSH AND SLAB PULL

Answer 6

Ridge push- magma rises as the plates move apart,magma cools to form new plate material.
As it cools it becomes denser and slides down the ridge which causes other plates to move away from each other

Slab pull-the denser plate( the new oceanic lithosphere)sinks back into the mantle under the influence of gravity and pulls the rest of the plate along behind it into the wadati-benioff sundiction zone.

Question 7

Explain Alfred Wegeners theory

Answer 7

A German meteorologist came up with the theory of continental drift that states that the continents gradually began to drift apart 300 million yrs ago and were all connected together before.

Question 8

What fossil did Wegener have to prove tat the continents were connected together before

Answer 8

Mesosaurus

Question 9

What rock and mountain evidence did Wegener have

Answer 9

Minerals in the rocks in Greenland and the UK were in line with the same magnetic field

Question 10

Why was Wegeners theory dismissed

Answer 10

At the time there was no explanation of how the continents moved

Question 11

Explain how the North Atlantic ridge demonstrates his theory (paleomagnetism)

Answer 11

The North Atlantic ridge demonstrates this theory as it proposes the idea of paleomagnetism;whereby the magmatic field of the earth changes every 400000 yrs whcih becomes synonymous with wegeners discovery of the minerals of rock in Greenland and the UK.

Question 12

What is subduction

Answer 12

Tectonic plate is forced under the mantle

Question 13

Why is the inner core made of solid,nickel

Answer 13

Due to the intense pressure and heat

Question 14

What plate is the most common?

Answer 14

Constructive margin
E.g. the indo Australian plate is moving away from Antarctica

Question 15

Explain the reasons why volcanoes are more likely along some plate boundaries?

Answer 15

Due to tectonic activity

1.convergent plate boundary(oceanic and continental )=subduction occurs due to differences in density.
High pressure and temperature creates magma (hydration melting) causes eruptions
Typically form volcanic arcs e.g. pacific ring of fire e.g. Andes mountains South America

2.divergent/constructiveplate boundary (2 oceanic plates)-move apart creating a gap which allows magma from the mantle to rise and fill the gap causing little pressure =magam from mantle rises creating new crust.expansion of seafloor causes effusive eruption

Question 16

2 characteristic of volcanic hotspots

Answer 16

1.hotspots-high heat and low pressure at the base of the lithosphere facilitates melting of rock which melts forming magma which rises thru cracks to form volcanoes

2.weak spots in crust-magma forces its way upward and may ultimately break through weak areas in crust