What is the epicentre of an earthquake?

the point on the surface directly above the focus. Shaking is usually strongest there.

Which type of volcano has gentle slopes and runny lava?

shield volcano. The lava flows a long way before it cools.

What is a dormant volcano?

one that has not erupted for a long time but may erupt again. "Dormant" means sleeping.

a mudflow of volcanic ash and water. It can follow river valleys for many kilometres.

What is a pyroclastic flow?

a fast-moving cloud of very hot gas and ash. It is the deadliest volcanic hazard.

What travels outwards from the focus of an earthquake?

seismic waves. They carry the energy that shakes the ground.

Earthquakes and volcanoes · Cambridge IGCSE Geography (9

In plain words

Plates do not slide smoothly. They stick, strain builds for years, and then they jerk. That is an earthquake. And where molten rock finds a way up through the crust, it builds a volcano.

8 things to know

An earthquake happens when stress built up between plates is suddenly released. The energy travels outwards as seismic waves.
The focus is the point inside the Earth where the earthquake starts. The epicentre is the point on the surface directly above the focus.
A strato-volcano (composite cone) is tall and steep, built of layers of ash and lava. Its lava is thick and sticky, and its eruptions are explosive. It forms at destructive boundaries.
A shield volcano is wide with gentle slopes. Its lava is runny and flows a long way, and its eruptions are gentle. It forms at constructive boundaries and over hotspots.
A cinder cone is a small, steep cone built from loose fragments thrown out of a single vent.
An active volcano has erupted recently and is likely to again. A dormant volcano has not erupted for a long time but could. An extinct volcano is not expected to erupt again.
Features: the magma chamber below, the vent that magma rises through, the crater at the top, and a secondary cone on the side.
Hazards: lava flows; ash falls; tephra, the fragments thrown out; toxic gases; lahars, which are fast mudflows of ash and water; and pyroclastic flows, which are clouds of very hot gas and ash that travel at great speed.

Worked example

Explain why pyroclastic flows are more dangerous to people than lava flows.

Lava usually moves slowly enough for people to walk away from it.
A pyroclastic flow moves far faster than a person or a car can.
It is extremely hot and full of ash and gas, so it destroys almost everything in its path.

Tips and tricks

Focus: underground. Epicentre: on the surface, directly above. Do not swap them.
Thick, sticky lava gives steep cones and explosions. Runny lava gives gentle slopes and gentle eruptions.

6 questions, about 2 minutes.

It lands in your notebook with its questions as flashcards.

Earthquakes and volcanoes: 6 questions and answers

These are the quiz’s questions. Do the quiz first, then come back here for the ones that got you.

What is the epicentre of an earthquake?
- the point underground where it starts
- the point on the surface directly above the focus (the answer)
- the edge of a plate
- the centre of the Earth
Shaking is usually strongest there.
Which type of volcano has gentle slopes and runny lava?
- strato-volcano
- shield volcano (the answer)
- cinder cone
- composite cone
The lava flows a long way before it cools.
What is a dormant volcano?
- one that is erupting now
- one that has not erupted for a long time but may erupt again (the answer)
- one that will never erupt again
- one under the sea
"Dormant" means sleeping.
What is a lahar?
- a cloud of gas
- a mudflow of volcanic ash and water (the answer)
- a type of lava
- a small earthquake
It can follow river valleys for many kilometres.
What is a pyroclastic flow?
- a slow river of lava
- a fast-moving cloud of very hot gas and ash (the answer)
- a flood of water
- falling snow
It is the deadliest volcanic hazard.
What travels outwards from the focus of an earthquake?
- lava
- ash
- seismic waves (the answer)
- magma
They carry the energy that shakes the ground.

6 questions

Tap an answer and you’ll see straight away whether it’s right, and why.

Worksheet

3 questions, 9 marks. Write your answers on paper, then check them.

Earthquakes and volcanoes

Cambridge IGCSE Geography (9–1) 0976 · 9 marks · papermunch.org

Name ______________________________ Date ______________

Describe the difference between the focus and the epicentre of an earthquake.[2]
Show answerHide answer
The focus is the point within the Earth where the earthquake begins. The epicentre is the point on the Earth's surface directly above the focus.
I got this one
Describe two differences between a strato-volcano and a shield volcano.[4]
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A strato-volcano has steep sides, but a shield volcano has gentle slopes. A strato-volcano has thick lava and erupts explosively, but a shield volcano has runny lava and erupts gently.
I got this one
Describe three volcanic hazards.[3]
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Lava flows that burn and bury land. Ash falls that collapse roofs and ruin crops. Pyroclastic flows: fast clouds of hot ash and gas. (Also: lahars, toxic gases.)
I got this one

Answers: Earthquakes and volcanoes

1. The focus is the point within the Earth where the earthquake begins. The epicentre is the point on the Earth's surface directly above the focus.
2. A strato-volcano has steep sides, but a shield volcano has gentle slopes. A strato-volcano has thick lava and erupts explosively, but a shield volcano has runny lava and erupts gently.
3. Lava flows that burn and bury land. Ash falls that collapse roofs and ruin crops. Pyroclastic flows: fast clouds of hot ash and gas. (Also: lahars, toxic gases.)