Major and minor forms of extrusive activity Flashcards Preview

A Level Geography - Plate tectonics and associated hazards > Major and minor forms of extrusive activity > Flashcards

Flashcards in Major and minor forms of extrusive activity Deck (14)
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1
Q

What are the 3 main MINOR extrusive features?

A

Geysers, hot springs and boiling mud.

2
Q

What are 2 good examples of MINOR extrusive feature sites?

A

Yellowstone National Park in the USA.

Various parts of Iceland.

3
Q

What are geysers and how are they formed?

+ EXAMPLE.

A

Water vent discharges the Earth’s surface.
Often intermittent/dangerous.
Surface water comes into contact with hot rocks - converted into steam.
Pressurised.
Fissure allows a jet of boiling water to explode onto the surface.
E.g. Old Faithful, Yellowstone National Park.

4
Q

How are hot springs formed?

+ EXAMPLE.

A

Groundwater is constantly heated by the rocks underneath the surface.
NOT pressurized so are therefore NOT explosive.
Temperatures 20-90C.
E.g. Mammoth Hot Springs.

5
Q

How is boiling mud formed?

A

Mud is mixed with heated volcanic water.
Causes it to bubble.
Acid attacks the surface and forms clay.
E.g. Yellowstone.

6
Q

When do minor extrusive features appear?

A

When an active volcano is nearing the end of its life.

Dormant volcano.

7
Q

What are the different types of volcanoes? 6

A
Fissure.
Shield.
Acid/dome.
Ash-cinder.
Composite/strato volcano.
Caldera.
8
Q

What is a lava plateaux volcano?

A

Fissure eruptions.
Basaltic - flow great distances.
Flat, layered.

9
Q

What is a shield volcano?

A
Basaltic.
Gentle sides
3 miles wide.
1,500m height.
Low gas content and silica.
E.g. Mauna Loa, Hawaii.
Constructive boundaries/hot spots.
10
Q

What is an acid/dome volcano?

A
Steep-sided - covered with rock debris.
Formed by repeated eruptions - a layered structure.
High silica and gas pressure.
Rhyolitic.
E.g. Puy Region, France.
11
Q

What is an ash-cinder volcano?

A

Formed from ash and volcanic bombs.
Steep and symmetrical sides.
E.g. Paricutin, Mexico.

12
Q

What are composite/strato volcanoes?

A

Tall, conical volcano built up by many layers (strata) of hardened lava, tephra, pumice, and volcanic ash.
High viscosity - andesitic.
E.g. Mount Etna/Pinatubo.

13
Q

What are caldera volcanoes?

A
Formed from HUGE explosions - blows the summit (top) of the cone off, leaving an opening.
Rhyolitic.
May become flooded by the sea.
Lake may form.
E.g. Yellowstone.
14
Q

What are solfataras?

A

Small volcanic areas without cones, produced by gases (mainly sulphurous) escaping to the surface.
E.g. Bay of Naples in Italy.