volcanoes Flashcards
what are volcanoes linked to?
plate tectonics and plate boundaries.
how many active volcanoes are there in the world?
500
what is the youngest volcano and when did it come from the ground?
Paricutin 1943
which volcano caused the year without summer?
Tambora, 1815
how many deaths were caused by Tambora?
60,000
how many deaths occurred with Krakatau?
36,417
how many deaths occurred with Pelee?
28,800
when did Pelee occur?
1902
when did Krakatau occur?
1883
what is the eruption magnitude related to?
logarithmically to the mass or volume of ejected material.
what magnitude is Yellowstone?
+9
which volcanoes are supervolcanoes?
yellowstone, Tambora, Mt St Helens
what are the different types of volcanoes?
shield volcanoes, stratovolcanoes, calderas and caldera complexes.
what lava does a shield volcano have?
balsaltic lava
what are the eruptions like in a shield volcano?
smaller, geographically contrainted eruptions, only explosive if water enters the vent.
what percentage of lava in in shield volcanoes?
90%, other is pyroclastic material
what percentage of the earth individual volcanoes are stratovolcanoes?
60%
what are the composition of stratovolcanoes?
andesite and dacite lava, which is more vocois than balsalt, allows gas pressure to build.
what are the eruptions like in stratovolcanoes?
more explosive eruptions due to the gas build-up. very dangerous
what percentage is lava in stratovolcanoes?
50% lava and 50% pyroclastic material
what type of eruptions are calderas?
most explosive volcanoes- supervolcanoes. then they erupt, they collapse on themselves.
which volanoes are calderas?
Koba, Yellowstone, Mt Vesuvius, Campi Flegrei.
what are the 4 types of eruptions?
Hawaiian, Stromolian, Vulcanian, Plinian.
what is a Hawaiin eruption?
basaltic, fluid lava, least threatening, few explosions, can last week. destroys everything in its path and ruins land
what is a Stromolian eruption?
discrete explosions at periods or seconds, to hours. ash columns and abundant ballistic debris, bomb lapilli and ash.
what is a Vulcanian eruption?
highly explosive, short lived, black ash and stream laden eruption.
what is a Plinian eruption?
the worst eruption, widely dispersed events, explosive areas of impacts. highly eruptive columns. produced Tephra and Volcanic Ash. debris avalanches, landslides, surges, blasts etc.
what happened in Montserrat?
eruptions began in July 1995, much of the island was evacuated. 1997- 19 people died n another eruption.
in Mountserrat, what was the main town buried in?
Pyroclastic flow.
what is volcano monitoring?
volcano observatories located in key regions, the key role in monitoring and early warning. detecting warning signs and provide the best mean to anticipate and mitigate against potential disasters.
where should volcano observatories be set up?
where there is threatened human populations and where it is possible to predict eruptive behaviour.
what lessons did they learn from Monserrat about basic sessions on human nature and society?
scientists, governors and local politicians tend to differ on what level of risk is acceptable. volcanology is an uncertain science, politicians dislike uncertainty. need good scientific information through fully communicated. buy-in trust regarding the management process.
when was the first Mt St Helen eruption?
1980, 57 people killed
what was unusual about the Mt St Helen eruption?
from 1964 to 1980 ther growth of the bulge was like no other volcano. lots of tremors. planes and roadbloacks were put into place, but many tourists came to the area.
what happened to Mt St Helen?
it exploded sideways, with a massive landslide of half of the volcano. volcanic ash and tephra, pyroclastic flow, and avalanches of debris. destroyed everything.
who died in Mt St Helen?
David Johnstone, a volcanologist.
what happened in Alaska 1989?
ash in a plane.
how many volcanoes does Alaska hold?
130
what happened with Alaska 2009 volcano?
there was an oil pope underneath the river and area of the volcano. technologist hazard. Redoubt volcano, all airlines stopped and nearly went bankrupt. took such a long time making a deciion whether to remove stored oil or not, that it was too late and had to evacuate.
what lesson was learned from Redoubt 2009?
political and economical pressures may act with or against caution of the threat. someone has to take charge and m=cakk the shots.
