Hazardous Earth - Tectonic Hazards

Question 1

What are the two main types of volcanoes

Answer 1

Shield Volcanoes and Compositive Volcanoes

Question 2

Where are shield volcanoes found

Answer 2

On constructive/ divergent plate boundaries or hotspots

Question 3

How are shield volcanoes formed

Answer 3

By eruptions of thin, runny lava which flows a long way before it solidifies

Question 4

What do shield volcanoes looks like

Answer 4

They have gently sloping sides and a wide base

Question 5

What do shield volcanoes comprise of (what are they made of)

Answer 5

They contain basaltic magma which is very hot with low silica and gas content

Question 6

Do shield volcanoes erupt frequently and violently?

Answer 6

They erupt erupt frequently but not violently

Question 7

Where are compositive volcanoes found

Answer 7

On destructive plate boundaries

Question 8

How are compositive volcanoes formed

Answer 8

By eruptions of viscous (or sticky) lava and ash that doesn’t flow far

Question 9

What are composites made up of

Answer 9

layers of thick lava and ash - contain andesitic magan which is less hot than basaltic magma but which contains lots of silica and gas

Question 10

What do composites look like

Answer 10

steep sloping sides and a narrow base. It has steep sides because the lava doesn’t flow very far before it solidifies; remember the lava is sticky not runny

Question 11

Do compositive volcanoes erupt frequently and violently

Answer 11

erupt infrequently but violently including lots of pyroclastic flows (mix of ash, gases and rock)

Question 12

What are the two points where energy produced by earthquakes is greatest

Answer 12

(i) Epicentre - point on surface directly above the focus
(2) Focus - central point of the earthquake deep under the surface

Question 13

Explain one reason why composite volcanoes are often more dangerous to humans than shield volcanoes

Answer 13

(i) While Shield volcanoes contain basaltic magma, which flows smoothly and is not full of gas, composite involves andesitic magma which contains a lot of silica.
(ii) Silica clogs up the volcano vent so pressure builds up in the volcano, along with large amounts of gas that make it explosive
(ii) This leads to very violent eruptions

Question 14

Define the term tsunami

Answer 14

Ocean wave that is triggered by a number of different causes, including earthquakes under the ocean

Question 15

Give two examples of recent tsunamis

Answer 15

2024 India Ocean and 2011 Tohoku (Japan)

Question 16

Explain how a tsunami is caused

Answer 16

They are a secondary effect of earthquakes that occur under the sea. They can also happen as a result of earthquakes on land that trigger landslides under the sea

Question 17

Where do volcanoes occur

Answer 17

At divergent plate boundaries or hot spots

Question 18

Explain one cause of volcanoes

Answer 18

With a volcano at a divergent plate boundary, convection currents in the mantle cause plates to move apart.
This usually happens under oceans
Magma rises to fill the rift valley between the plates.
Where it breaks through the surface of the earth, it forms a shield volcano
Chains of volcanoes can build up e.g. the Mid Atlantic Ridge