Volcanic Vocabulary
1.
Volcanic ash – the powdery residue of matter that
remains after burning.
2.
Active volcano – is an volcano that has at least one
eruption during the past 10,000 years
3.
Caldera – a large volcanic crater, typically one
formed by a major eruption leading to the collapse
of the mouth of the volcano
4.
Cinder cone volcano – deposit volcanic vent, formed
by pyroclastic rock fragments (formed by volcanic or
igneous action), or cinders which accumulate and
gradually build a conical hill with a bowl-shaped
crater at the top
5.
Composite (strato) volcano - comprise the largest
percentage (~60%) of the Earth's individual
volcanoes and most are characterized by eruptions
of andesite and dacite - lavas that are cooler and
more viscous than basalt.
6.
Crater - a large, bowl-shaped cavity in the ground or
on the surface of a planet or the moon, typically one
caused by an explosion or the impact of a meteorite
or other celestial body
7.
Dormat volcano - is an active volcano that is not
erupting, but supposed to erupt again
8.
Eruption - lava, tephra (ash, lapilli, volcanic bombs
and blocks), and various gases are expelled from a
volcanic vent or fissure.
9.
Extinct volcano – Includes includes volcanos which
scientists consider unlikely to erupt again.
10. Hot spot - are volcanic regions thought to be fed by
underlying mantle that is anomalously hot compared
with the mantle elsewhere.
11. Lava - hot molten or semifluid rock erupted from a
volcano or fissure, or solid rock resulting from cooling of
this.
 Magma - hot fluid or semifluid material below or
within the earths crust from which lava and other
igneous rock is formed by cooling.
12. Viscosity - the state of being thick, sticky, and
semifluid in consistency, due to internal friction.
13. Pipe (Conduit) - it resists flow very well, the gas
bubbles will have a hard time escaping from the
magma, and so will push more material up, causing
a bigger eruption.
14. Pyroclastic flow - density current) is a fast-moving
current of hot gas and rock (collectively known as
tephra), which reaches speeds moving away from a
volcano of up to 700 km/h (450 mph).
15. Ring of fire - is an area where a large number of
earthquakes and volcanic eruptions occur in the
basin of the Pacific Ocean.
16. Shield volcano - a broad, domed volcano with gently
sloping sides, characteristic of the eruption of fluid,
basaltic lava.
17. Vent - is an opening exposed on the earth's surface
where volcanic material is emitted.
18. Volcanic neck - a column of solidified lava or
igneous rock formed in a volcanic vent, especially
when exposed by erosion.
19. Pluton - a body of intrusive igneous rock.
 Sill - a tabular sheet of igneous rock intruded
between and parallel with the existing strata
 Laccolith - a mass of igneous rock, typically lensshaped, that has been intruded between rock strata
causing uplift in the shape of a dome.
 Batholith - a very large igneous intrusion extending
deep in the earth's crust.
 Dike - Dikes are imaginable as the veins of a volcano,
the pathways of rising magma.
20. Intraplate volcano - volcanic activity that occurs
within tectonic plates and is generally NOT related to
plate boundaries and plate movements.
Questions
1.
In general, how do volcanoes form? Volcanoes form
when magma from within the Earth’s upper mantle
works its way to the surface.
2. What are the main parts of a volcano? (Be able to label
them on the diagram) The different parts of the volcanoes
are:
 Magma – Molten rock beneath Earth’s surface
 Parasitic Cone – A small cone-shaped volcano formed
by an accumulation of volcanic debris.
 Sill - A flat piece of rock formed when magma
hardens in a crack in a volcano.
 Vent - An opening in Earth's surface through which
volcanic materials escape.
 Flank - The side of a volcano.
 Lava - Molten rock that erupts from a volcano that
solidifies as it cools.
 Crater - Mouth of a volcano - surrounds a volcanic
vent.
 Conduit - Underground passage magma travels
through.
 Summit - Highest point; apex
 Throat - Entrance of a volcano. The part of the
conduit that ejects lava and volcanic ash.
 Ash - Fragments of lava or rock smaller than 2 mm in
size that are blasted into the air by volcanic
explosions.
 Ash Cloud - A cloud of ash formed by volcanic
explosions.
3. What causes a volcano to erupt? injection of new
magma into a chamber that is already filled with magma
of similar or different composition. This injection forces
some of the magma in the chamber to move up in the
conduit and erupt at the surface.
www.scientificamerican.com/.../what-causes-a-volcano-t.
4. How does a volcano erupt? The lower density of the
magma relative to the surrounding rocks causes it to rise
(like air bubbles in syrup). It will rise to the surface or to
a depth that is determined by the density of the magma
and the weight of the rocks above it.