Plate Tectonics

Question 1

Describe the structure of the Earth (layers and composition) - Plate Tectonics

Answer 1

The Earth is made up of 4 layers -
Crust: aluminium, silicone, potassium. 0-40km
Mantle: silicate rocks. 40-300km
Outer core: iron/nickel
Inner core: molten iron and nickel

Question 2

What is the crust and mantle divided into? - Plate Tectonics

Answer 2

The crust and mantle are divided into the lithosphere and asthenosphere.
Lithosphere - crust and upper mantle, mainly solid
Asthenosphere - semi-molten area beneath the lithosphere, deformable under pressure and responsible for convection currents.

Question 3

What are the 2 types of crust? What are their characteristics (density, rock type) - Plate Tectonics

Answer 3

Oceanic crust - basalt, denser than continental

Continental crust - granite (mostly), lighter than oceanic so rides atop denser plates.

Question 4

What causes the movement of tectonic plates? - Plate Tectonics

Answer 4

Tectonic plates move when convection currents in the mantle (caused by heating from the core) drag plates around due to the fluid nature of the asthenosphere.

Question 5

What creates the heating of the mantle that moves tectonic plates? - Plate Tectonics

Answer 5

The decay of radioactive isotopes in the core generates heat, as well as from the heat remaining from the formation of the Earth.

Question 6

Describe the theory of ridge push with regards to the movement of tectonic pates - Plate Tectonics

Answer 6

Ridge push occurs when the asthenosphere is heated at constructive (divergent) boundaries, with the spilling upwards of magma cooling and solidifying. This the slides down a slope, dragging with it the tectonic plates and contributing to their movement.

Question 7

Describe the tectonic process of slab pull with regards to the movement of tectonic plates - Plate Tectonics

Answer 7

Slab pull occurs at destructive plate boundaries, where a denser oceanic plate sinks beneath continental plates. As the oceanic plate subducts beneath the continental plate, this drags the rest of the oceanic plate with it.

Question 8

What is Pangea? What evidence exists of this existing? - Plate Tectonics

Answer 8

Pangea is a supercontinent that existed prior to continental drift, which has evolved into creating the landmasses we know today. This can be evidenced by the interlocking theory, geological/climatological/biological evidence and palaeomagnetism.

Question 9

What is the interlocking theory? How does this evidence continental drift? - Plate Tectonics

Answer 9

The interlocking theory is based around the idea that continents appear to have interlocking edges that fit together, such as Africa and South America. This demonstrates that at one point, continents had interlocked and have since drifted apart.

Question 10

What evidence exists in terms of plants and animals of continental drift? - Plate Tectonics

Answer 10

Plants - North America and Europe contain some evidence of the same fossilised plants that belong in tropical regions. Suggests not only that continents were once close, but that these have moved from a tropical position.
Animals - some fossils found across multiple continents, suggesting continents were at one stage connected.

Question 11

How does glaciation provide evidence of continental drift? - Plate Tectonics

Answer 11

Previous glaciation in continents now distant from polar regions imply that continents may have once existed at the extremities of the Earth and have since moved away.

Question 12

Describe what happens at destructive (collision) plate boundaries and destructive (subduction) plate boundaries - Plate Tectonics

Answer 12

Collision: 2 plates of equal or similar densities meet and neither plate is able to subduct, causing these plates to be forced up into fold mountains
Subduction: 2 plates of different densities move towards each other, with the denser plate (usually oceanic) subducting beneath the lighter plate.

Question 13

What is the Benioff Zone? - Plate Tectonics

Answer 13

The Benioff Zone is the area in which subducting plates melt in the mantle and form the material which contributes to volcanoes.

Question 14

What hazards are found at destructive plate margins? What are characteristic landforms? - Plate Tectonics

Answer 14

Hazards: composite volcanoes, earthquakes, viscous lava flows and explosive earthquakes.
Landforms: fold mountains, oceanic hazards, island arcs.

Question 15

Describe what happens at constructive boundaries - Plate Tectonics

Answer 15

At constructive boundaries, 2 plates move apart, causing basaltic lava to spill out and fill this gap, continuously creating new crust.

Question 16

What hazards are associated with constructive plate boundaries? What are characteristic landforms of these boundaries? - Plate Tectonics

Answer 16

Hazards: sub-marine/shield volcanoes, earthquakes (shallow focus)
Characteristic landforms: ocean ridges/rift valleys.

Question 17

Describe what happens at conservative boundaries - Plate Tectonics

Answer 17

2 plates move alongside each other in the same direction but at differing speeds. No volcanic activity occurs at these boundaries, yet can cause shallow focus earthquakes.

Question 18

Describe how young fold mountains form. What plate boundary? - Plate Tectonics

Answer 18

Young fold mountains form when 2 plates move together at a collisional boundary, warping rocks in an upwards direction and folding them into rocky hills and mountains.

Question 19

How long does the process of forming fold mountains take? What are associated hazards with this landform? Give an example of fold mountains - Plate Tectonics

Answer 19

Fold mountains take millions of years to form as 2 plates move together very slowly. These are commonly associated with light upward movement of magma. A well known set of fold mountains includes the Himalayas, the Andes and the Alps.

Question 20

Describe the formation of rift valleys. What plate boundary? - Plate Tectonics

Answer 20

Rift valleys are formed at constructive plate boundaries, where the lithosphere is stretched and fragmented by this movement. The land between these faults collapses into valleys within land.

Question 21

What are associated landforms and hazards resulting from rift valleys? Give an example of a Rift Valley - Plate Tectonics

Answer 21

Landforms: new ocean may eventually form in the valley.
Hazard: valley is a potential hazard, earthquakes, volcanic activity.
Examples: the East African Rift Valley.

Question 22

Describe the formation of ocean ridges. What plate margin? - Plate Tectonics

Answer 22

Ocean ridges are formed at constructive margins. The heat from the mantle deforms the lithosphere, causing plates to uplift into mountain ranges at ridges. Magma may also move upwards to fill this gap and form igneous rocks which become part of the Earth’s crust.

Question 23

What are hazards associated with ocean ridges? Give an example of an ocean ridge- Plate Tectonics

Answer 23

Hazards: submarine volcanoes, shallow focus earthquakes

An example of a an ocean ridge is the East Pacific Rise.

Question 24

Describe the differing characteristics of slowly spreading ridges and rapidly spreading ridges - Plate Tectonics

Answer 24

Slowly spreading: tall and narrow ridges

Rapidly spreading: gentler sloping sides.

Question 25

Describe the formation of deep sea trenches? What plate margin? Give an example of a deep sea trench - Plate Tectonics

Answer 25

Deep sea trenches formed at subduction plate margins when denser oceanic plates subduct beneath continental plates. Creates a gentle slope on the oceanic side and a steep drop on the continental side.
An example of a deep sea trench is the Peru-Chile Trench.

Question 26

Describe the formation of island arcs. What plate margin? - Plate Tectonics

Answer 26

2 oceanic plates move towards each other, with the denser plate subducting beneath the lighter one. This causes magma to rise through the Benioff zone, forming volcanoes which eventually create island arcs.

Question 27

What are hazards associated with island arcs? Give examples of island arcs - Plate Tectonics

Answer 27

Hazards: volcanic islands

The Mariana Islands in the West Pacific are an example of Island Arcs.