Chapter 05 Vocab Flashcards
accretionary lapilli
Hailstone-like clumps of wet ash that fall from a volcanic eruptive cloud.
active volcano
A volcano that has erupted within the past few centuries and will likely erupt again.
ash
Tiny glass shards formed when a fine spray of exploded lava freezes instantly upon contact with the atmosphere.
blocky lava
Lava that is so viscous that it breaks into boulder-like blocks as it moves; typically, such lavas are andesitic or rhyolitic.
bomb
A large piece of pyroclastic debris thrown into the atmosphere during a volcanic eruption.
caldera
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.
cinder cone
A subaerial volcano consisting of a cone-shaped pile of tephra whose slope approaches the angle of repose for tephra.
columnar jointing
A type of fracturing that yields roughly hexagonal columns of basalt; columnar joints form when a dike, sill, or lava flow cools.
crater
(1) A circular depression at the top of a volcanic mound; (2) a depression formed by the impact of a meteorite.
dormant volcano
A volcano that has not erupted for hundreds to thousands of years but does have the potential to erupt again in the future.
effusive eruption
An eruption that yields mostly lava, not ash.
eruptive style
The character of a particular volcanic eruption; geologists name styles based on typical examples (e.g., Hawaiian; Strombolian).
explosive eruptions
Violent volcanic eruptions that produce clouds and avalanches of pyroclastic debris.
extinct volcano
A volcano that was active in the past but has now shut off entirely and will not erupt in the future.
fissure
A conduit in a magma chamber in the shape of a long crack through which magma rises and erupts at the surface.
flood basalt
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.
hyaloclastite
A rubbly extrusive rock consisting of glassy debris formed in a submarine or sub-ice eruption.
ignimbrite
Rock formed when deposits of pyroclastic flows solidify.
lahar
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.
lapilli
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.
large igneous province (LIP)
A region in which huge volumes of lava and/or ash erupted over a relatively short interval of geologic time.
lava tube
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.
magma chamber
A space below ground filled with magma.
pahoehoe
A lava flow with a surface texture of smooth, glassy, rope-like ridges.
pumice lapilli
Marble-sized chunks consisting of frothy, siliceous igneous rock that fall from a volcanic eruptive cloud.
pyroclastic debris
Fragmented material that sprayed out of a volcano and landed on the ground or sea floor in solid form.
pyroclastic flow
A fast-moving avalanche that occurs when hot volcanic ash and debris mix with air and flow down the side of a volcano.
scoria cone
(also “cinder cone”) An accumulation of lapilli-sized or larger fragments formed from a volcanic eruption that spatters clots of basaltic lava.
shield volcano
A subaerial volcano with a broad, gentle dome, formed either from low-viscosity basaltic lava or from large pyroclastic sheets.
stratovolcano
A large, cone-shaped subaerial volcano consisting of alternating layers of lava and tephra.
supervolcano
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.
tephra
Unconsolidated accumulations of pyroclastic grains.
tuff
A pyroclastic igneous rock composed of volcanic ash and fragmented pumice, formed when accumulations of the debris cement together.
vesicles
Open holes in igneous rock formed by the preservation of bubbles in magma as the magma cools into solid rock.
volcano
(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.
