GHC Ch 7: Volcanism Cont. Flashcards Preview

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Flashcards in GHC Ch 7: Volcanism Cont. Deck (18):
1

Rifting at spreading centers worldwide creates (...) km3 of new oceanic crust each year.

20

2

In Iceland, a volcanic plateau built of (...) erupted from hot spot underlying mid-Atlantic Ocean spreading center.

basaltic lava

3

Most of world’s famous volcanoes are (...) volcanoes.

subduction zone

4

Many regions around subduction zone volcanoes are (...) populated.

heavily

5

Erupt directly into atmosphere (not underwater) so have (...) impact on worldwide climate

direct

6

Subduction of (...) plate under (...) plate is responsible for Cascade Range volcanoes

Juan de Fuca, North American

7

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

8

Eruption frequency: Mt. St. Helens?

At least 15 important eruptions in 4000 years

9

About (...) people killed during last (...) years by about (...) volcanic processes.

275,000, 500, a dozen

10

Pyroclastic Processes in flows?

superhot, high speed turbulent cloud of ash, gas and air

11

Pyroclastic Processes in flows results in about what percent of volcanic deaths?

29%

12

Volcano-generated tsunami have been responsible for what percent of volcano-caused deaths?

21%

13

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

14

VEI is?

a semi-quantitative estimate of magnitude of volcanic eruption, using volume erupted and eruption-column height.

15

Signs of Impending Eruption?

Seismic Waves, Ground Deformation, Gas Measurements

16

At least how many active or potentially active volcanoes in U.S.?

65

17

How do volcanoes cause tsunamis?

caldera collapse, undersea eruptions, travel of pyroclastic flows, lahars, and debris avalanches.

18

How do we monitor active volcanoes?

Volcano Observatories