Vulcanicity Theory

Question 0

5 intrusive volcanic landforms?

Answer 0

1) dykes- vertical intrusions coming from the batholith with horizontal cooling cracks. They cut across bedding planes of rock into which they have been intruded (many Scottish Islands have clusters of dykes such as Skye)
2) sills- horizontal intrusions along lines of bedding planes with vertical cooling cracks (examples include the great whin sill)
3) batholith- large emplacement of igneous intrusive rock that forms from cooled magma deep in the earths crust.
4) laccolith- formation in which lava is trapped beneath the surface of the earth and pushes up into a dome shape.
5) volcanic neck/plug- landform created when lava cools within a vent on an active volcano (causing pressure build up)

Question 1

What is vulcanicity?

Answer 1

Refers to the physical processes and landforms created by magma pushing it’s way through the earths crust

Question 2

Name four lava flows?

Answer 2

1) pahoehoe lava flow- thin with low visc, surface cools and forms skin, travels far.
2) A’A’ lava flow- higher visc, balsatic and andesitic lava, rough surface due to broken lava blocks called clinker.
3) pillow lava- lava erupts under water and surface skin forms rapidly, look like inflated balloons of lava.
4) tephra/pyroclasts- fragments of rock ejected by the volcanoe (ash, lapilli, blocks and bombs, pumice, spatter etc)

Question 3

Extrusive landforms?

Answer 3

1) volcanoes
2) geysers
3) boiling mud
4) hot springs
5) lava plateaus

Question 4

Fissure volcanos

Answer 4

Gentle slopes, liquid lava flows widespread from fractures. Examples include Columbia river plateau.

Question 5

Shield volcanoes.

Answer 5

Liquid lava from main vent. Examples include Mauna Loa, Hawaii

Question 6

Acid dome volcanoes

Answer 6

Explosive liquid lava from small central vent. Examples include mount unzen, japan.

Question 7

Ash and cinder cone volcanos

Answer 7

Viscous explosive debris, large, emitted from central vent. Examples include mount fox, Queensland Australia.

Question 8

Composite volcanoes

Answer 8

Viscous and explosive yet fairly small. Examples include st Augustine in Alaska

Question 9

Calderas volcanos

Answer 9

Sides subside due to earth movement. Fills with water forming lake. Examples include Crate Lake Caldera, O’Regan USA

Question 10

Characteristics of a constructive eruption?

Answer 10

1) mainly lava
3) basalt
3) viscous
4) shield or lava plateau
5) frequent
6) effusive

Question 11

Characteristics of a destructive eruption?

Answer 11

1) ash and dust not lava ejected
2) rhyolite
3) composite cone
4) infrequent
5) explosive!

Question 12

Positive impacts on an eruption?

Answer 12

• igneous rocks make excellent building materials. In Aberdeen most buildings are made of granite.
• lava flows can create new land, for example the islands of hawaii.
• tourist attractions which can create huge revenues.
• extinct volcanos have made excellent defensive sites. For example Edinburgh castle.
• igneous rocks contain valuable minerable deposits including gold and diamonds!

Question 13

Negative impacts of volcanic eruptions?

Answer 13

• lava flows burn and bury crops
• coastal eruptions can cause tsunamis for example the 1883 eruption in Krakatoa in Indonesia caused waves up to 40m killing over 36,000 people
• lava and ash weathers quickly into fertile soil
• dust emissions endanger air transport for example Ejafjallajokull in 2010
• volcanic dust absorbs solar energy and so lowers atmospheric temperatures. Eg the 2001 eruption of mount pinatubo in the phillipenes caused global temps to lower by 0.6 degrees c for the next 1-2 years after