Vulcanicity

Question 1

What is a batholith?

Answer 1

They are magma chambers that have solidified deep below the surface. They cool slowly which allows large crystals to form and therefore they are mostly made out of granite.

Question 2

What is a sill?

Answer 2

Sills are horizontal intrusions along lines of bedding planes. Magma vent that cooled before reaching the surface.

Question 3

What is a dyke?

Answer 3

Vertical intrusions that form because the magma cools before getting to the surface.

Question 4

What are Andesitic and rhyolitic lava characteristics?

Answer 4

Formed in silica-rich magma
Viscous lava
Often solidifies before reaching the surface –> a build up of pressure and leading to a violent explosion

Question 5

What are the characteristics of basaltic lava?

Answer 5

Formed in low silica magma

Allows gas bubbles to expand on the way up to the surface –> preventing sudden explosive activity

Question 6

Name the six main extrusive volcanic landforms.

Answer 6

Lava plateaux
Shield/basic volcano
Acid/dome volcano
Ash and cinder cones
Composite cones
Calderas

Question 7

What is a lava plateaux and how are they formed?

Answer 7

Flat featureless landforms
Formed from fissure eruptions
Basaltic lava flows that go a long distance
e.g: Antrim lava plateau, Northern Ireland

Question 8

What is a shield volcano and how are they formed?

Answer 8

Formed from runny lava
Gentle sides
Cover a large area
e.g: Mauna Loa, Hawaii

Question 9

What is an acid/dome volcano and how are they formed?

Answer 9

Steep sides and convex shape
Viscous lava
E.g: Puy region of central France

Question 10

What are ash and cinder cones and how are they formed?

Answer 10

Formed by ash, cinders and volcanic bombs ejected from a crater
Steep sides
Symmetrical
E.g: Paricutin, Mexico

Question 11

What are composite cones and how are they formed?

Answer 11

Classic pyramid shape
Layers of ash and lava
Thick lava
E.g: Mount Etna, Sicily

Question 12

What are calderas and how are they formed?

Answer 12

Gases build up and causes a huge explosion which removes the summit of the cone and leaves an opening.
E.g: Santorini, Greece

Question 13

Name 3 minor volcanic forms.

Answer 13

Solfatara
Geysers
Hot springs/boiling mud

Question 14

What is solfatara?

Answer 14

Small volcanic areas without cones
Produced by gases (mainly sulfurous) escaping to the surface
E.g: Bay of Naples, Italy

Question 15

What are geysers?

Answer 15

Water, heated by volcanic activity, explodes onto the surface.
E.g: Old Faithful, Yellowstone National Park, USA

Question 16

What are hot springs?

Answer 16

Water heated by volcanic activity but doesn’t explode to the surface.
If this water mixes with mud then it makes boiling mud.
These occur all over Iceland
There are hot springs in Bath, England.

Question 17

What are the primary effects of volcanic eruptions?

Answer 17

Tephra (volcanic bombs and ash ejected into the atmosphere)
Pyroclastic flows (Very hot, gas charged, high velocity flows made up fomr gases and tephra)

Question 18

What are the secondary effects volcanic eruptions?

Answer 18

Lahars (boiling hot mud flows, occurs on snow topped volcanoes)
Flooding (melting of glaciers and ice caps)
Tsunamis (formed by violent caldera collapses)
Landslides
Climatic change (reduction in temperature because the sun’s energy blocked)