Unstable Earth

Question 1

List two types of natural hazards.

Answer 1

Hydro-meteorological hazards and tectonic hazards

Question 2

What are the three (four) layers of the earth?

Answer 2

(From out to in) crust, mantle, (outer and inner) core

Question 3

What order are the layers of the Earth arranged in?

Answer 3

The layers are arranged according to their density. The layers with less density come on top.

Question 4

What are the Earth’s major plates?

Answer 4

North American Plate, South American Plate, Eurasian Plate, Pacific Plate, Indo-Australian Plate, Nazca Plate

Question 5

List three differences between oceanic crust and continental crust.

Answer 5

Oceanic crust: make up ocean floors, thinner, more dense

Continental crust: make up continents, thicker, less dense

Question 6

What are the minerals making up oceanic crust and continental crust?

Answer 6

Oceanic crust: silica, magnesium

Continental crust: silica, aluminium

Question 7

What is one risk of the two types of crust meeting at one point?

Answer 7

Oceanic crust will be subducted under Continental crust due to its higher density, and the constantly high pressure at the subduction point can lead to earthquakes.

Question 8

List all types of plate boundaries.

Answer 8

Constructive plate boundary, destructive plate boundary, conservative plate boundary

Question 9

How is constructive plate boundary formed?

Answer 9

Constructive plate boundary is formed when the convection currents of magma push two adjacent plates away from each other. The magma rises from the cracks and becomes new crust or volcanoes.

Question 10

How is destructive plate boundary formed?

Answer 10

destructive plate boundary is formed when oceanic crust and continental crust move towards each other by the force of the convection currents of magma. The oceanic crust is subducted under the continental crust due to its higher density, and pressure builds up in the subduction zone. Eventually, the pressure and friction is overcome and the plates slip, resulting in earthquakes. The crust is melted in the subduction zone and magma rises, forming volcanoes.

Question 11

How is conservative plate boundary formed?

Answer 11

Conservative plate boundary is formed when two plates move in the same or opposite directions by the force of convection currents of magma, but at different speeds. Pressure is built up because of heavy friction at the plate boundary. Eventually, the friction is overcome and the plates slip, resulting in earthquakes.

Question 12

List three examples of primary impacts of earthquakes.

Answer 12

Ground shakes, buildings collapse, liquefaction

Question 13

List three examples of secondary impacts of earthquakes.

Answer 13

Fire outbreaks due to ruptured gas lines, disease outbreak, agricultural loss due to tsunami or landslide

Question 14

What is liquefaction?

Answer 14

The state of land behaving like a fluid usually because of leaking of underground water pipes

Question 15

Describe the distribution of earthquakes.

Answer 15

About 90% of the earthquakes are formed along plate boundaries. There are two main earthquake zones: Circum-Pacific Belt and Alpine-Himalayan Belt.

Question 16

What is the epicentre of an earthquake?

Answer 16

The point right above the focus of the earthquake (which is where the pressure is first overcome and the rocks first break)

Question 17

What are released from the focus and transmit energy in all directions?

Answer 17

Seismic waves

Question 18

Describe the relationship of the intensity of shaking and the distance from the epicentre.

Answer 18

The shorter the distance, the higher the intensity, because there are less rocks in the crust to absorb the energy released by the earthquake.

Question 19

Describe the relationship between the damage of the earthquake and the depth of the focus. Suppose the earthquake releases the same amount of energy no matter how deep the focus is.

Answer 19

The deeper the focus, the less damage the earthquake does, because there are more rocks from the focus to the epicentre to absorb the energy released by the earthquake.

Question 20

What are the scales used to measure earthquakes? How are they similar and different from each other?

Answer 20

Richter scale and modified Mercalli scale. They are both recorded in levels (richter: 1-9; Mercalli:1-12). However, the Richter scale measures the amount of energy released, which is more objective, whereas the Mercalli scale measures subjective observations made about the earthquake.