Block:A large angular lava
fragment which is thrown out during an eruption.
Usually 1m or more across.
Bomb:Bombs are large, rounded, lava
fragments thrown out during an eruption.
They are often modified in shape during their flight or upon impact.
Caldera: A huge bowl-shaped crater,
often kilometres across, formed by collapse into the magma
chamber or by explosive volcanic eruptions.
Cinders:Light fragments of lava,
between 64mm and 30cm in size. Also named scoria.
Cinder cone: A steep conical hill
formed above a vent,
usually less than 250m high. Also named scoria-cone.
Complex Volcano: A volcano
that consists of a complex of two or more vents, or
that has an associated dome,
either in its crater
or on its flanks.
Volcano: A steep volcanic cone composed of lava
fragments as well as other volcanic products. Also called strato-volcano.
Compound Volcano:See Complex
passage followed by magma in
Drift:Theory formed by the German scientist Alfred Wegener. According to the theory
continents move in consequence of the movement of plates
which move in consequence of convection
Crater:A bowl-shaped, steep-sided,
hollow in the summit of a volcano
which lies above the vent from
which volcanic material is expelled.
Crust:The thin outermost layer of
the Earth, forming both the continents and the ocean floors.
Debris Avalanche:A rapid mass
movement that may include volcanic rock, water, snow, glacier ice, trees and other pyroclastic
Dome: Domes form
when a dome-shaped mass of volcanic rock is too viscous
to flow far from the vent.
They are often formed on composite
volcanoes at the end of an eruption.
Dormant Volcano:A volcano
which is presently inactive but which may erupt again.
Eruption:The way liquids, solids
and gases are expelled on the Earth's surface by volcanic activity. This can range from
explosive outbursts to quiet, noiseless lava-outcome.
Resources Observation System)
which is not currently erupting and which isn't likely to do so in the future.
Fissure: A crack or fracture in the
or the slope of a volcano,
up which magma
Flood Basalt: Large-scale
outpourings of basalt lava
producing thick accumulations.
Fumarole:A vent or
opening giving off gases
or steam. Fumaroles occur on both active
Hot Spot:Fixed places within the mantle
where rocks melt to generate magma.
highly associated with water.
Lahar:Mudflows formed by the mixing
of volcanic particles and water.
Landslide:downslope movement of a
mass of bedrock under the influence of gravity.
molten rock which reaches the Earth's surface exposed to air or water. Lava occurs as flows,
fragments within cones of volcanoes
and as pillows formed on the ocean floor.
which is outpoured in a flow on the land from a vent or fissure.
Examples of lava flows include aa and pahoehoe
Lithosphere:The solid outer shell
of the Earth which is composed of the Earth's crust
and the solid outermost layer of the mantle.
The lithosphere lies above the asthenosphere.
It is broken up into plates.
Maar:German word used to describe a
which is almost circular. The crater
is usually filled with (rain)water.
Magma: Very hot,
molten rock which is formed within the earth by partial melting of the mantle.
chamber:A chamber(cavity or reservoir) in the lithosphere
where rising magma is
"collected" and halts for varying lengths of time.
Mantle:The intermediate zones
between the Earth's crust
Nu ardente:French word used
to describe a glowing avalanche of hot gas and other volcanic fragments of all size(like ash,
rock debris, etc.).
Oceanic Ridge:Ridge on the ocean
floor where two adjacent plates
diverge and where new crust is
generated by volcanic eruptions.
Pahoehoe:Hawaiian term used to
describe thin, smoothly flowing, lava
flows with a glassy plastic skin.
Eruption:A sudden violent eruption
of steam which is caused when water and heated volcanic rocks interact.
characterised by steam explosions caused by the interaction of rising magma
and surface water.
Pillow lava:Interconnected lobs of lava
formed underwater by submarine
Plate:Plates are huge slabs into
which the crust
as well as the upper part of the mantle
Plate Tectonics:Theory dealing with
and their activity.
Eruption:One of the most explosive types of eruptions,
known for producing nu嶪s ardentes and lahars.
solidified in the conduit
of an extinct
so bubbly that it floats in water.
Pyroclastic:Adjective used to
describe rock material formed by a volcanic explosion.
Pyroclastic Flow:Mixtures of hot gas
travelling very quickly down the slope of a volcano.
Ring of Fire:The belt of volcanoes
that surround the Pacific Ocean. This belt contains about two-thirds of the world's active
volcanoes. It is marked by the volcanic chains of Japan, Kamchatka, South Alaska, the
Aleutian Islands, the Cascade Range of the US and Canada, Central America, the Andes, New
Zealand, Tonga, Vanuatu, Papua- New Guinea, Indonesia, the Philippines, and last but not
least the Mariana, Izu and Bonin Islands which complete the circle.
Seafloor spreading:The process in
which the ocean floor is extended when two plates
Seismograph:An instrument that is
used to record vibrations of the Earth.
which has a broad shaped cone with gently slopes. Shield volcanoes
are built by runny lava
Silica:Fundamental component of
volcanic rocks. It is the most important factor determining the fluidity of magma.
The higher the silica of a magma
the greater its viscosity.
Solfatara:Italian word used to
describe a fumarole
that emits sulphurous gases.
fragments, between 64mm and 30cm in size. which are often emitted as hot clots. Spatter
often welds together to form steep-sided cones.
Spatter cone:Steep-sided cone of
Stratosphere:The upper layer of the
Eruption: Short-lived eruptions
that throw out blocks
Subduction:The process in which one
is pushed downward beneath another plate
into the underlying mantle
move towards eachother.
noun for all sorts of volcanic material that are erupted from a crater
Tremor:Earthquake activity with a
low amplitude associated with the movement of magma.
Tsunami:Japanese word that is used
to describe huge sea-waves generated by earthquakes or violent volcanic eruptions.
Tuff Cone:Steep conical hill with a
deep, wide crater.
The cone is composed of thin layers of fine fragments. A tuff cone is smaller and steeper
than a tuff
Tuff Ring:A broad, circular,
low-rimmed, well-bedded accumulation of fine fragments, often 1km in diameter, around a crater.
of a tuff ring is wider than the one of a cinder
Vent:The vent is an opening at the
Earth's surface through which volcanic materials are released.
Viscosity:Term to show how sticky a
Volcanic Ash:Volcanic rock which is
exploded from a vent in
fragments less than 2mm in size. Ash may be solid or molten when first erupted.
Volcanic Gas:Volcanic gas is
contained within magma.
As the magma
rises to the Earth's surface the gases are exsolved and can become a very important factor
in the violence of an eruption.
Because some gases are toxic they can suffocate people. Examples of volcanic gases include
steam, sulphur dioxide and carbon dioxide.
Volcano:A cone which is formed
above and around a vent by
accumulations of erupted volcanic materials like ash,
flows and other volcanic rocks. "Volcano" can refer to both the vent and
Volcanologist:A person who studies volcanoes
and their behaviour.
Volcanology:The science of volcanoes.
Vulcan:God of fire of the ancient
Romans. The volcano
is named after Vulcan.
Eruption:A Vulcanian Eruption is similiar to hydrovolcanic
activity. Much gas
as well as ash,
and pumice are given off.