Chapter 05 Vocab

Question 1

accretionary lapilli

Answer 1

Hailstone-like clumps of wet ash that fall from a volcanic eruptive cloud.

Question 2

active volcano

Answer 2

A volcano that has erupted within the past few centuries and will likely erupt again.

Question 3

ash

Answer 3

Tiny glass shards formed when a fine spray of exploded lava freezes instantly upon contact with the atmosphere.

Question 4

blocky lava

Answer 4

Lava that is so viscous that it breaks into boulder-like blocks as it moves; typically, such lavas are andesitic or rhyolitic.

Question 5

bomb

Answer 5

A large piece of pyroclastic debris thrown into the atmosphere during a volcanic eruption.

Question 6

caldera

Answer 6

A large circular depression with steep walls and a fairly flat floor, formed after an eruption as the center of the volcano collapses into the drained magma chamber below.

Question 7

cinder cone

Answer 7

A subaerial volcano consisting of a cone-shaped pile of tephra whose slope approaches the angle of repose for tephra.

Question 8

columnar jointing

Answer 8

A type of fracturing that yields roughly hexagonal columns of basalt; columnar joints form when a dike, sill, or lava flow cools.

Question 9

crater

Answer 9

(1) A circular depression at the top of a volcanic mound; (2) a depression formed by the impact of a meteorite.

Question 10

dormant volcano

Answer 10

A volcano that has not erupted for hundreds to thousands of years but does have the potential to erupt again in the future.

Question 11

effusive eruption

Answer 11

An eruption that yields mostly lava, not ash.

Question 12

eruptive style

Answer 12

The character of a particular volcanic eruption; geologists name styles based on typical examples (e.g., Hawaiian; Strombolian).

Question 13

explosive eruptions

Answer 13

Violent volcanic eruptions that produce clouds and avalanches of pyroclastic debris.

Question 14

extinct volcano

Answer 14

A volcano that was active in the past but has now shut off entirely and will not erupt in the future.

Question 15

fissure

Answer 15

A conduit in a magma chamber in the shape of a long crack through which magma rises and erupts at the surface.

Question 16

flood basalt

Answer 16

Vast sheets of basalt that spread from a volcanic vent over an extensive surface of land; they may form where a rift develops above a continental hot spot, and where lava is particularly hot and has low viscosity.

Question 17

hyaloclastite

Answer 17

A rubbly extrusive rock consisting of glassy debris formed in a submarine or sub-ice eruption.

Question 18

ignimbrite

Answer 18

Rock formed when deposits of pyroclastic flows solidify.

Question 19

lahar

Answer 19

A thick slurry formed when volcanic ash and debris mix with water, either in rivers or from rain or melting snow and ice on the flank of a volcano.

Question 20

lapilli

Answer 20

Any pyroclastic particle that is 2 to 64 mm in diameter (i.e., marble-sized); the particles can consist of frozen lava clots, pumice fragments, or ash clumps.

Question 21

large igneous province (LIP)

Answer 21

A region in which huge volumes of lava and/or ash erupted over a relatively short interval of geologic time.

Question 22

lava tube

Answer 22

The empty space left when a lava tunnel drains; this happens when the surface of a lava flow solidifies while the inner part of the flow continues to stream downslope.

Question 23

magma chamber

Answer 23

A space below ground filled with magma.

Question 24

pahoehoe

Answer 24

A lava flow with a surface texture of smooth, glassy, rope-like ridges.

Question 25

pumice lapilli

Answer 25

Marble-sized chunks consisting of frothy, siliceous igneous rock that fall from a volcanic eruptive cloud.

Question 26

pyroclastic debris

Answer 26

Fragmented material that sprayed out of a volcano and landed on the ground or sea floor in solid form.

Question 27

pyroclastic flow

Answer 27

A fast-moving avalanche that occurs when hot volcanic ash and debris mix with air and flow down the side of a volcano.

Question 28

scoria cone

Answer 28

(also “cinder cone”) An accumulation of lapilli-sized or larger fragments formed from a volcanic eruption that spatters clots of basaltic lava.

Question 29

shield volcano

Answer 29

A subaerial volcano with a broad, gentle dome, formed either from low-viscosity basaltic lava or from large pyroclastic sheets.

Question 30

stratovolcano

Answer 30

A large, cone-shaped subaerial volcano consisting of alternating layers of lava and tephra.

Question 31

supervolcano

Answer 31

A volcano that erupts a vast amount (more than 1,000 cubic km) of volcanic material during a single event; none have erupted during recorded human history.

Question 32

tephra

Answer 32

Unconsolidated accumulations of pyroclastic grains.

Question 33

tuff

Answer 33

A pyroclastic igneous rock composed of volcanic ash and fragmented pumice, formed when accumulations of the debris cement together.

Question 34

vesicles

Answer 34

Open holes in igneous rock formed by the preservation of bubbles in magma as the magma cools into solid rock.

Question 35

volcano

Answer 35

(1) A vent from which melt from inside the Earth spews out onto the planet’s surface; (2) a mountain formed by the accumulation of extrusive volcanic rock.