Eruption Styles & Eruptions Flashcards
Hawaiian
Gentle eruption of of basalt lava. Gas release may produce a lava fountain. Lava flow (aa, pahoehoe; scoria cone from lava fountaining
Strombolian
Minor explosions every few minutes. Spasmodic gas release from basalt lava. Cinders and bombs build a scoria cone.
Vulcanian
Moderately violent explosive gas blast; eruption column. Andesite lava. Air-fall deposits (pumice).
Plinian
Sustained vertical gas blast; high eruption column. Rhyolite lava. Air-fall deposit; pyroclastic flows/surges from eruption column collapse.
Peleean
Collapse (explosice or gravitational) of a lava dome. Andesite to Rhyolite lava. Pyroclatic surge/flow is directed.
Erupting
A volcano with eruption taking place.
Active
A volcano that has erupted in the last 10,000 years.
How many volcanoes worldwide are active right now?
More than 1500
Dormant
Not active, but will erupt again.
Repose time
Average length of time between eruptions
Extinct
Will not erupt again… ever!
What is an eruption?
Ejection of lava and/or rock fragments; excludes gas venting between eruptions. Eruptions are not necessarily continuous, long-running eruptions have stages or episodes.
What is the primary trigger for eruptions?
Vesiculation because it pressurizes the magma chamber
What are other triggers for eruptions?
Magma chamber recharge, earthquakes, and rainfall
Magma chamber recharge (fresh basalt)
When fresh mantle-derived magma’s injected into magma chamber, it causes a volume problem so an eruption occurs to keep homeostasis in chamber volume.
