Flashcards in Major and minor forms of extrusive activity Deck (14):
What are the 3 main MINOR extrusive features?
Geysers, hot springs and boiling mud.
What are 2 good examples of MINOR extrusive feature sites?
Yellowstone National Park in the USA.
Various parts of Iceland.
What are geysers and how are they formed?
Water vent discharges the Earth’s surface.
Surface water comes into contact with hot rocks - converted into steam.
Fissure allows a jet of boiling water to explode onto the surface.
E.g. Old Faithful, Yellowstone National Park.
How are hot springs formed?
Groundwater is constantly heated by the rocks underneath the surface.
NOT pressurized so are therefore NOT explosive.
E.g. Mammoth Hot Springs.
How is boiling mud formed?
Mud is mixed with heated volcanic water.
Causes it to bubble.
Acid attacks the surface and forms clay.
When do minor extrusive features appear?
When an active volcano is nearing the end of its life.
What are the different types of volcanoes? 6
What is a lava plateaux volcano?
Basaltic - flow great distances.
What is a shield volcano?
3 miles wide.
Low gas content and silica.
E.g. Mauna Loa, Hawaii.
Constructive boundaries/hot spots.
What is an acid/dome volcano?
Steep-sided - covered with rock debris.
Formed by repeated eruptions - a layered structure.
High silica and gas pressure.
E.g. Puy Region, France.
What is an ash-cinder volcano?
Formed from ash and volcanic bombs.
Steep and symmetrical sides.
E.g. Paricutin, Mexico.
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.
What are caldera volcanoes?
Formed from HUGE explosions - blows the summit (top) of the cone off, leaving an opening.
May become flooded by the sea.
Lake may form.