Chapter 5: Volcanic Eruptions

Question 1

lava flow

Answer 1

the term used for both the molten, moving mass of lava and for the solid layer of rock that forms when the lava freezes

Question 2

basaltic lava flows

Answer 2

• low viscosity (fast)

- it can flow farther/longer distances than felsic lava

Question 3

andesitic lava

Answer 3

• higher viscosity
• doesn’t flow very far from the plume/volcano
• tends to break up as it flows

Question 4

felsic lava

Answer 4

• very high viscosity

- may pile up in a dome shape around the

Question 5

pillow lava

Answer 5

common in underwater basaltic flows; lava creates a glass blobs where lava keeps flowing into, the blob breaks open, lava flows out creating another blob, and this process keeps repeating

Question 6

tephra or pyroclastic debris

Answer 6

unconsolidated fragments resulting from a volcanic eruption

Question 7

what types of eruptions are caused by rhyolitic and andesitic lavas?

Answer 7

since these lavas are more viscous (slow) and are generally richer in gases, their eruptions tend to be more explosive and eject large quantities of pyroclastic debris

Question 8

lahar

Answer 8

wet, ash-rich, rapidly flowing debris flow

Question 9

shield volcanoes

Answer 9

broad, gentle domes whose shape resembles a soldiers shield lying on the ground: form as a result of low viscosity (fast) eruptions which do not mound up, but spread out in wide sheets over large areas

Question 10

cinder cones

Answer 10

aka scoria cones

cone-shaped piles of basaltic lapilli and blocks; steep slopes are the angle of repose for lapilli

Question 11

stratovolcanoes

Answer 11

aka composite volcanoes
large volcanoes (up to 3km high and 25km across) that consist of interleaved layers of lava, tephra, and volcanic debris; this results in stratovolcanoes having internal layering (STRATO); steeper slopes at the summit, gentle slopes nearer the base

Question 12

effusive eruption

Answer 12

lava spills or fountains steadily from a vent or fissure; might flow downslope

Question 13

tectonic setting for volcanoes

Answer 13

• mid-ocean ridges
• convergent boundaries (island and continental arcs)
• continental rifts (divergent boundaries)
• ocean and continental hot spot volcanism

Question 14

active volcanoes

Answer 14

volcanoes that are erupting, have recently erupted, or are likely to erupt within decades

Question 15

dormant volcanoes

Answer 15

volcanoes that have not erupted for hundreds to thousands of years, but might erupt again in the future

Question 16

extinct volcanoes

Answer 16

volcanoes that have shut off entirely and will never erupt again