Flashcards in Major and minor forms of extrusive activity Deck (14):
1
What are the 3 main MINOR extrusive features?
Geysers, hot springs and boiling mud.
2
What are 2 good examples of MINOR extrusive feature sites?
Yellowstone National Park in the USA.
Various parts of Iceland.
3
What are geysers and how are they formed?
+ EXAMPLE.
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
How are hot springs formed?
+ EXAMPLE.
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
How is boiling mud formed?
Mud is mixed with heated volcanic water.
Causes it to bubble.
Acid attacks the surface and forms clay.
E.g. Yellowstone.
6
When do minor extrusive features appear?
When an active volcano is nearing the end of its life.
Dormant volcano.
7
What are the different types of volcanoes? 6
Fissure.
Shield.
Acid/dome.
Ash-cinder.
Composite/strato volcano.
Caldera.
8
What is a lava plateaux volcano?
Fissure eruptions.
Basaltic - flow great distances.
Flat, layered.
9
What is a shield volcano?
Basaltic.
Gentle sides
3 miles wide.
1,500m height.
Low gas content and silica.
E.g. Mauna Loa, Hawaii.
Constructive boundaries/hot spots.
10
What is an acid/dome volcano?
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
What is an ash-cinder volcano?
Formed from ash and volcanic bombs.
Steep and symmetrical sides.
E.g. Paricutin, Mexico.
12
What are composite/strato volcanoes?
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
What are caldera volcanoes?
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