Volcanoes, Earthquakes, Tsunamis Flashcards
Intrusions
Magma cooling in a chamber below the ground
Extrusions
Magma escaping the ground to the surface
Pumice
Solidified bubbling magma
Andesite
- Extrusive rock, formed by moderate viscosity lava
- Intermediate silica content caused by the partial melting of basalt in subduction zones
Fumaroles
Fissures near active volcanoes that emit steam and volcanic gases
Effusive/Hawaiian eruption
- Occur when hot, (1200oC) runny basalt magmas reach the surface
- Dissolved gases escape easily as the magma erupts, forming lava that flows downhill quite easily.
- Effusive eruptions build up gently-sloping Shield Volcanoes like Hawaii.
Plinian Eruption
- Large explosive eruptions that form enormous dark columns of tephra and gas high into the stratosphere
- Named for Pliny the Younger, who carefully described the disastrous eruption of Vesuvius in 79 A.D.
Strombolian eruption
- Volcanic eruption with relatively mild blasts
- VEI of 1-3
- Consist of ejection of incandescent cinders, lapilli, and lava bombs, to altitudes of tens to a few hundreds of metres
Vulcanian eruption
- Volcanic eruption characterized by a dense cloud of ash-laden gas exploding from the crater and rising high above the peak
- Smaller than a Plinian eruption
Peléan eruptions
- Viscous magma, typically of rhyolitic or andesitic type
- Presence of a pyroclastic flow
- Formation of lava domes, short flows of ash or creation of pumice cones may be observed as well
Intermediate flows (Andesite)
- Composite cone
- 55% silica
- Quite vicious
- Partial melting of basalt in subduction
Acidic/Felsic/Granitic flows
- 70% silica
- extremely vicious
- Usually doesn’t erupt and cools in magma chambers
- Partial melting of sediments dragged into subduction
Supervolcanoes
Large granitic eruptions
Ignimbrites
Rocks formed from pumice-dominated pyroclastic flow deposits
Caldera
Large hollow that forms shortly after the emptying of a magma chamber in a volcanic eruption
Flood basalt
- Giant volcanic eruption/series of eruptions that covers large stretches of land/ocean floor with basalt lava
- Many flood basalts have been attributed to the onset of a hotspot reaching the surface
Pillow lava
Pillow-shaped structures attributed to the extrusion of the lava underwater
Basaltic lava flows
Hawaiian volcanism or undersea constructive volcanism
The least viscious eruption, highly liquid flows, non-explosive, forms shield volcanoes
