GHC Ch 7: Volcanism Cont. Flashcards
Rifting at spreading centers worldwide creates (…) km3 of new oceanic crust each year.
20
In Iceland, a volcanic plateau built of (…) erupted from hot spot underlying mid-Atlantic Ocean spreading center.
basaltic lava
Most of world’s famous volcanoes are (…) volcanoes.
subduction zone
Many regions around subduction zone volcanoes are (…) populated.
heavily
Erupt directly into atmosphere (not underwater) so have (…) impact on worldwide climate
direct
Subduction of (…) plate under (…) plate is responsible for Cascade Range volcanoes
Juan de Fuca, North American
At subduction zones, (…) is melted (aided by water released from sediments on top of subducting plate) and mixes with (…) yielding (…).
upper mantle (asthenosphere), melted crustal rock, rising (mixed) andesitic magma
Eruption frequency: Mt. St. Helens?
At least 15 important eruptions in 4000 years
About (…) people killed during last (…) years by about (…) volcanic processes.
275,000, 500, a dozen
Pyroclastic Processes in flows?
superhot, high speed turbulent cloud of ash, gas and air
Pyroclastic Processes in flows results in about what percent of volcanic deaths?
29%
Volcano-generated tsunami have been responsible for what percent of volcano-caused deaths?
21%
What are Lahars? What cause them?
Lahars are volcanic mudflows and volcanic debris flows that are fluid when moving, but then solidify soon after stopping. Water + loose pyroclasts + steep slopes
VEI is?
a semi-quantitative estimate of magnitude of volcanic eruption, using volume erupted and eruption-column height.
Signs of Impending Eruption?
Seismic Waves, Ground Deformation, Gas Measurements
