Tectonic Plates, Volcanoes, and Earth Structure test 2023

Question 1

What is the crust?

Answer 1

The crust is the rocky, outer layer of the earth. It is made of rock and is solid. About 5 - 70kms deep. Thinnest layer.

Question 2

What is the mantle?

Answer 2

The second layer of the earth composed of thick, plastic-like molten rock. The temperature at nearer to the crust is about 500 - 1000 Celsius, lower mantle 2000 - 3000 degrees Celsius due to heat. and 2,850 km thick.

Question 3

What is the outer core?

Answer 3

The third layer of the earth composed of a liquid iron-nickel mixture. About 2200km thick and around 3000 - 5000 degrees Celsius

Question 4

What is the inner core?

Answer 4

The deepest layer of the earth made of solid (due to pressure) iron and nickel. About 5000 degrees Celsius and 1270 km thick.

Question 5

What are the two types of crust?

Answer 5

Oceanic and continental

Question 6

What is oceanic crust?

Answer 6

Thinner crust found underneath the ocean, about 5 - 10 km deep. Thinner but denser (made of basalt) than continental crust.

Question 7

What is continental crust?

Answer 7

Thick crust about 20 - 70km deep. Thicker but lighter than oceanic crust.

Question 8

What is the lithosphere?

Answer 8

The outer part of the earth made up of the crust and mantle

Question 9

What is the asthenosphere?

Answer 9

The upper part of the mantle, near the crust where convection currents form and underneath the lithosphere on which it sits. Called the plastic layer

Question 10

What are tectonic plates?

Answer 10

Puzzle - piece-like slabs of rock that fit together and make up the crust. They converge, diverge, and transform slowly against each other. Part of the lithosphere

Question 11

Why and how fast do tectonic plates move

Answer 11

Plates move about 0 -15cm each year. Move due to convection currents in the mantle.

Question 12

What are convection currents? How are they formed?

Answer 12

Convection currents are heat-driven cycles in the mantle that move tectonic plates. As magma nearer to the outer core in the mantle gets hotter, it rises to the crust. Coolermagma sinks back down. This rising and sinking cycle pushes the plates around the earth.

Question 13

Who theorized plate tectonics?

Answer 13

Alfred Wegener

Question 14

How many main tectonic plates are there?

Answer 14

7

Question 15

What are the 3 plate boundaries?

Answer 15

Convergent, Divergent, Transform

Question 16

What is a convergent boundary?

Answer 16

Where tectonic plates smash into each other. Creates volcanoes, mountains (regular or folded), earthquakes (largest occur here), ocean ridges, and tsunamis. Can also cause subduction. Also called a destructive boundary.

Question 17

What is subduction?

Answer 17

When two plates converge, one plate may sink below the other (typically oceanic as it is denser). It melts in the mantle, bringing up hot magma. This magma can rise up through the crust and create volcanoes.

Question 18

What is a divergent boundary?

Answer 18

Where plates move apart from each other. Creates volcanoes and small earthquakes, seafloor spreading, rift valleys, and ocean ridges. Is also called a constructive boundary.

Question 19

What happens at an oceanic-oceanic convergent boundary?

Answer 19

As they collide, one plate subducts under one another. This can create a rift valley. The melted plate in the magma can also rise and create a chain of volcanoes. Can also cause earthquakes and tsunamis.

Question 20

What happens at an oceanic-continental convergent boundary?

Answer 20

The oceanic crust subducts underneath the continental crust as it is heavier. In the subduction zone, it creates trenches, and on land, it can create volcanoes.

Question 21

What happens at a continental-continental convergent boundary?

Answer 21

As continental crust is to light to subduct, they collide and push upwards, creating mountains, like fold mountains.

Question 22

What is a transform boundary?

Answer 22

Where two plates side either in opposite directions or the same directions at different speeds. Creates faultlines, earthquakes and rarely volcanoes.

Question 23

What happens at an oceanic-oceanic divergent boundary?

Answer 23

As the crust pulls apart, it forms a mid-ocean ridge. The thinning of the crust allows magma to seep through and create underwater volcanoes (where then eruptions cause seafloor spreading).

Question 24

What happens at a continental-continental divergent boundary?

Answer 24

The pulling apart action creates a long depression in the earth known as a rift valley. Magma can rise through the thinned crust to create volcanoes.

Question 25

What is continental drift?

Answer 25

The hypothesis that continents have spread or floated over time.

Question 26

About 200 million years ago, what was the single-continent land mass called?

Answer 26

Pangaea

Question 27

What is the ring of fire?

Answer 27

The region around the rim of the Pacific ocean where up to 80% of seismic/volcanic activity occurs. This is as it traces around where many tectonic boundaries are located.

Question 28

How are volcanoes formed?

Answer 28

Usually form at plate boundaries, however, can form by:
1. Subduction zones (convergent) - excess of magma from molten rock rises through the crust and creates volcanoes
2. Rift valleys (divergent) - a gap in separated plates allow magma to rise up
3. Hotspots - a highly active magma spot in the middle of a plate

Question 29

What are the 2 main types of volcanoes

Answer 29

1. Stratovolcanoes - meaning “layered volcano” in Latin, stratovolcanoes are formed from viscous magma that piles and hardens into rock. This process repeats, creating a new layer of rock with each eruption. Characterised by steep, sloping sides.
2. Sheild volcanoes - stumpy, wide, rounded volcanoes that are formed from more liquidy magma that spreads wide.

Question 30

Where do earthquakes occur?

Answer 30

Anywhere but mostly along plate boundaries or Ring of Fire

Question 31

What is the process of producing an earthquake - transform?

Answer 31

1. Two plate boundaries rub and catch against each other causing friction
2. Pressure from catch builds
3. Pressure builds till it is too much for the catch to handle and the plates suddenly slip past each other

Question 32

What is the process of producing an earthquake divergent/convergent boundary?

Answer 32

When a plate suddenly moves, can shake the whole plate

Question 33

What is the focus (earthquake)?

Answer 33

The point underground where the slip happens/point where earthquake originates

Question 34

What is the epicentre?

Answer 34

The point on the ground directly above the focus.

Question 35

What is a fault/faultline?

Answer 35

A weak part of the tectonic plate where the pressure is released and creates a linear rock break.

Question 36

What are seismic waves?

Answer 36

Wave-like vibrations sent out before, during, and after an earthquake

Question 37

What is a foreshock?

Answer 37

A mild tremor before the main earthquake. A smaller quake however cannot be classified as a foreshock if a major earthquake does not occur afterwards. Can occur hours to days after the quake.

Question 38

What is an aftershock?

Answer 38

A mild tremor after as a result of an earthquake. Can occur hours to weeks after the quake.

Question 39

How are earthquakes measured?

Answer 39

Quakes are measured in magnitude by using the Richter scale or other scales such as moment magnitude scales. THey are recorded via a seismograph

Question 40

How does the Richter scale work?

Answer 40

Measures the size of the waves produced by a quake, scaled from 1 - 9. Each successive number is 10x stronger than the previous. Eg. a magnitude 5 quake is 10x stronger than a 4, whilst an 8 would be 100,000x larger than a 4.

Question 41

What is a tsunami?

Answer 41

A large, powerful surge of displaced water is typically caused by earthquakes.