🟠✅Natural Hazards - Plate Theory

Question 1

Constructive plate boundary

Answer 1

Divergent, moving apart

Gaps created so magma rises and forms new crust / volcanoes

Transform fault lines

Rift valleys - Red Sea (African + Arabian)
Ridge system - Mid Atlantic Ridge (Eurasian + N.American)

Question 2

Conservative plate boundary

Answer 2

Plates sliding past each other

Frequent earthquakes, plates stick together and friction and energy build up. When the plates unstick from each other large amounts of energy is released.

Fault lines - San Andres Fault (Pacific + N.American)

Question 3

Destruction plate boundary

Answer 3

Subduction zone - Oceanic + continental OR oceanic + oceanic

The plate converge and the heavier oceanic plate subducts under the less dense oceanic/continental plate

The oceanic plate can melt and can form volcanoes

Ocean trenches, V-shaped depressions (Pacific under Philippine = Mariana Trench)
Island arcs

Question 4

Collisional plate boundary

Answer 4

2 continental converging plates

The 2 continental crusts collide and the crust crumples and uplifts creating fold mountains

Fold mountains - Himalayas (Eurasian + Indian)

Question 5

Earths structure

Answer 5

Crust
Mantle
Outer core
Inner core

Question 6

Describe the Crust (location / thickness / characteristics / density / materials)

Answer 6

Outer layer

6-70km

Thin / hard and rigid. Separated into oceanic and continental plates

Lightest

Granite and basalt

Question 7

Describe the Mantle (location / thickness / characteristics / density / materials)

Answer 7

2nd layer

2900km

Hot and semi molten / convection currents / lithosphere (soils rock)

Light

Magnesium / lead / aluminium / silicon

Question 8

Describe the Outer Core (location / thickness / characteristics / density / materials)

Answer 8

3rd layer

2300km

Liquid

Dense

Mainly iron and nickle

Question 9

Describe the Inner Core (location / thickness / characteristics / density / materials)

Answer 9

Centeral

1200km

Highest pressure

Densest

Solid - iron and Nickle

Question 10

Continental crust

Answer 10

35-70km
Very old over 1500million years old
Light – average density 2.6g/cm3
Rocks – numerous types – granite common
Minerals SIAL – upper levels of the earth’s crust - Silica and aluminium (absent in ocean basins)
Cannot be destroyed
Mainly granite

Question 11

Oceanic crust

Answer 11

6-10km
V young under 200 million years old
Heavier – average density 3.0g/cm3
Few rock types mainly Basalt
Minerals SIMA – lower levels of the Earth’s crust silica and magnesium
Can be renewed/destroyed
Mainly basalt

Question 12

What is the plate tectonic theory

Answer 12

Explains the global distribution of geological phenomena. Principally it refers to the movement and interaction of the earth’s lithosphere. This includes the formation, movement, collision and destruction of plates and the resulting geological events such as seismicity, volcanism, continental drift, and mountain building.

Question 13

Plume theory

Answer 13

Hot spot volcanoes occur far from plate boundaries. Because the hot spot is caused by mantle plumes that exist below the tectonic plates, as the plates move, the hot spot does not, and may create a chain of volcanoes on the Earth’s surface.

Question 14

Hot spot

Answer 14

An area on Earth over a mantle plume or an area under the rocky outer layer of Earth, called the crust, where magma is hotter than surrounding magma.

Question 15

Magma plume definition

Answer 15

A magma plume causes melting and thinning of the rocky crust and widespread volcanic activity

Question 16

Convection currents - plate tectonic theory

Answer 16

1. Heat from inner core converts through mantle into asthenosphere.
2. Hot magma rises because it becomes less dense with heat (as particles spread out).
3. Magma is cooler at the top as its further away from heat source. Becomes more dense and sinks back down to the bottom.
4. Cooler magma is reheated and begins to rise again creating a loop called a convection current.