Tectonic Hazards

Question 1

Describe the makeup of the Earths?

Answer 1

The Earths mantle is semi-molten 5000oc
The centre of the Earth= the core= inner core 5500oc and outer core
Outside this there’s the mantle, the layer within the mantle, but below the lithosphere (crust)= ASENOSPEHRE

Question 2

What’s the theory of Plate Reactions?

Answer 2

The lithosphere is divided into lots of slabs called tectonic plates

Question 3

Compare oceanic and continental crust?

Answer 3

OCEANIC- thinner and more dense

• (6-10km)
• Basaltic Rock
• Goes under (subducts) under continental plates
• Younger than continental- 3.0p (density)

CONTINENTAL- thicker and less dense

• (30-70km)
• Granitic Rock
• Doesn’t subduct
• Older than oceanic- 2.6p (density)

Question 4

What takes place at Constructive margins?

Answer 4

VOLCANOES, EARTHQUAKES, OCEAN RIDGE, RIFT VALLEY
-two plates move apart and “diverge”
-the mantle is under pressure from plates above and when plates pull apart magma rises (less dense than plate above)
When pressure builds a plate can crack causing a fault line and making an EARTHQUAKE

Question 5

What specific landforms can be found at constructive plates?

Answer 5

OCEAN RIDGE- plates diverge UNDERWATER
eg: Mid Atlantic Ridge- a mostly underwater mountain range

RIFT VALLEY- plates diverge and causes the continental crust between two parallel faults to drop eg: East African Rift Valley

Question 6

Exam point Answer of what happens at CONSTRUCTIVE margins?

Answer 6

• plates diverge
• convection currents diverge and gap is created between the plates
• magma (less dense) rises up to fill the gaps created
• rift valleys can be created if plates pull apart and the land drops to create a valley eg: East African Rift System

Question 7

What takes place at Destructive margins?

Answer 7

VOLCANOES, EARTHQUAKES, DEEP SEA TRENCH, ISLAND ARCS, FOLD MOUNTAINS- plates converge

Oceanic- continental= more dense oceanic is forced under continental= deep sea trench at destructive subduction boundaries

Oceanic- oceanic= the more dense of the two is forced under the other, volcanic eruptions that take place underwater create ISLAND ARCS eg: Marina Islands

Continental- continental= FOLD MOUNTAINS- made up of sediments that have accumulated on continental crust

Question 8

Exam point Answer of what happens at Destructive Plates?

Answer 8

• oceanic plate (denser) subsides beneath continental crust
• crust is DETSTROYED as one plate moves under another at the SUBDUCTION zone
• rocks catch against each other as plates aren’t smooth
• pressure builds until the plates can’t take the stress- they SLIP past each other causing the ground to shake

Question 9

What takes place at Conservative margins?

Answer 9

ONLY EARTHQUAKES
When two plates are moving past eachother- the two plates get locked together in places and pressure builds up eg: Pacific Plate moving past North American Plate
= San Andreas Fault in California

Question 10

Exam point Answer of what happens at Conservative Plates?

Answer 10

• Plates slide past each other horizontally
• Crust is neither created or detroyed
• The plates are made of rock that has jagged edges so they snag and PRESSURE AND FRICTION builds up
• The plates SLIP past each other= EARTHQUAKES

Question 11

When did Plato theorise the earths structure consisted of multiple spheres?

Answer 11

2000 YEARS AGO

Question 12

What specific shape is the Earth?

Answer 12

A geoid- it bulges at the equator and is flatter at the plates.

Question 13

What is continental crust also known as?

Answer 13

Sial Crust

Question 14

What is oceanic crust also known as?

Answer 14

Sima

Question 15

What does the lithosphere consist of?

Answer 15

The crust and upper mantle. It is the zone that tectonic plates are formed.(Rigid)

Question 16

What does the asthenosphere consist of?

Answer 16

Lies directly below the Lithosphere and includes the rest of the mantle where rocks are much softer. (Plastic)

Question 17

What is the Moho discontinuity?

Answer 17

The boundary between the crust and mantle.

Question 18

Which tectonic theory did Alfred Wegner propose?

Answer 18

A German Meteorologist

Proposed the theory of “continental drift”

Question 19

What evidence is there of the continental drift theory?

Answer 19

• Coal has been found in Antarctica= unlikely to have formed as needs tropical climates and dense vegetation
• Upper carboniferous glaciation found in the southern hemisphere

Question 20

What did the CONTINENTAL DRIFT theory evolve into and differences?

Answer 20

PLATE TECTONIC THEORY
-seismometers monitored the ground shaking and found that earthquakes occurred on specific plates than equally over the earth

• states the crust is broken up into 20 sections
• explains why the earth’s crusts are moving

CONTINENTAL DRIFT

• hypothesised all modern day continents had been previously clumped together in a “supercontinent” called PANGEA
• Wegner stated that over millions of the years Pangea had drifted apart
• Reconfiguration= a “Pangea Proximia”

Question 21

What is intra plate volcanism?

Answer 21

Plate activity AWAY from the plate boundary.

Question 22

What happens when two continental plates at a destructive margin (convergent) collide?

Answer 22

Creates fold mountains as subduction doesn’t occur, land bulges upwards.
Folding of layers of lithosphere.

eg: Himalayas

Question 23

What happens when two destructive plates at a destructive margin (convergent) meet?

Answer 23

The faster, more sense plate subducts under the other.

Question 24

How to hot-spots (intra-plate volcanism) form?

Answer 24

=STATIONARY action away from a plate boundary
Form due to concentrated spots of radioactive decay in the core

Concentrated spots of radioactive decay heat the lower mantle= MAGMA PLUME forms= rises vertically.

Question 25

Define “magma-plume”?

What do magma plumes cause?

Answer 25

A vertical column of extra-hot magma that rises from the mantle.

They cause intense volcanic activity away from plate margins.

Question 26

How was Hawaii formed?

Answer 26

-Magma plume forms which cause extreme volcanic activity away from the plate margin
-Volcanoes form above the magma plume
-The magma plume stays stationary over time but the crust moves about it
-Volcanic activity deceases at specific parts of the crust where it moves away
-New volcanoes form above the magma plume/ hotspot
=CHAIN of volcanoes= HAWAII

Question 26

How was Hawaii formed?

Answer 26

-Magma plume forms which cause extreme volcanic activity away from the plate margin
-Volcanoes form above the magma plume
-The magma plume stays stationary over time but the crust moves about it
-Volcanic activity deceases at specific parts of the crust where it moves away
-New volcanoes form above the magma plume/ hotspot
=CHAIN of volcanoes= HAWAII

Question 27

What are the two main types of plate movement?

Answer 27

FOLDING-Two plates come together and push against each other
Ripples at the surface form
High points of ripples= anticlines
Low points of ripples= synclines

FAULTING- Usually parallel in a “fault zone”

• DIPSLIPS (vertically up and down)
• STRIKE SLIPS (horizontally left to right)
  eg: San Andreas Fault- Pacific and NA plate.

Question 28

What can marine erosion and subsidence cause to happen to volcanic hotspots?

Answer 28

Marine erosion and subsidence can reduce these hotspot volcanoes to seamounts, which may form coral atolls overtime.