During a volcanic eruption, lava
, solid chunks of
), and various gases, are expelled from a volcanic vent
Several types of volcanic eruptions
distinguished by volcanologists
These are often named after famous volcanoes
where that type of behavior has been observed. Some volcanoes may
exhibit only one characteristic type of eruption during a period of
activity, while others may display an entire sequence of
Volcanic eruptions arise through three main mechanisms:
produce juvenile clasts during
explosive decompression from gas release. They range in size from
the relatively small fire fountains on Hawaii to >30 km
Ultra Plinian eruption columns, bigger than the eruption that
buried Pompeii. (Heiken & Wohletz 1985)
Strombolian eruptions are
named because of activity of Stromboli in Sicily.
characterised by huge clots of molten lava
bursting from the summit
to form luminous arcs through
the sky. Collecting on the flanks of the cone, lava clots combine
to stream down the slopes in molten rivulets. The explosions are
driven by bursts of gas slugs that rise faster than surrounding
Vulcanian eruptions are
named after Vulcano, following
Giuseppe Mercalli's observations
of its 1888-1890 eruptions. Another example was the eruption of
Parícutin in 1947.
They are characterised by a dense
cloud of ash-laden gas exploding from the crater and rising high
above the peak. Steaming ash forms a whitish cloud near the upper
level of the cone.
Peléan eruption or nuée ardente (glowing cloud) eruption, such
as occurred on the Mayon
Volcano in the Philippines in 1968, a large amount of gas, dust, ash, and lava
fragments are blown out of a central crater, fall back, and form
avalanches that move downslope at speeds as great as 160 km
per hour. Such eruptive activity can cause great
destruction and loss of life if it occurs in populated areas, as
demonstrated by the devastation of Saint-Pierre during the 1902 eruption of Mont Pelée on Martinique, Lesser Antilles,
from which Peléan eruptions are named.
Hawaiian eruptions may occur
along fissures or fractures that serve as vents, such as during the
eruption of Mauna Loa
Volcano in Hawaii in 1950. Also, they can occur
at a central vent, such as during the 1959 eruption in Kilauea Iki
Crater of Kilauea Volcano,
In fissure-type eruptions, lava shoots from
a fissure on the volcano's rift zone
feeds lava streams that flow downslope. In central-vent eruptions,
a lava fountain
is erupted to a height
of several hundred meters or more. Such lava may collect in old
to form lava lakes
, or form cones, or feed radiating
A Surtseyan eruption
occurs in shallow seas
. It is named after the
island of Surtsey off the
southern coast of Iceland.
are usually the most powerful,
and involve the explosive ejection of relatively viscous lava.
plinian eruptions — such as during 18 May 1980 at
Mount St. Helens or, more recently, during 15
June 1991 at Pinatubo in the Philippines— can send ash and volcanic gas tens of kilometres
into the atmosphere.
The resulting ash fallout can affect
large areas hundreds of miles downwind. Fast-moving pyroclastic surges
and pyroclastic flows
together with “nuées
ardentes,” are often associated with plinian eruptions.
are the result of
thermal contraction from chilling on contact with water. The
products of phreatomagmatic eruptions are believed to have more
regular shard shapes and be finer grained than the products of
magmatic eruptions because of the different eruptive
There is debate about the exact nature of the eruptive style.
Fuel-coolant reactions may be more critical to the explosive nature
than thermal contraction (Starostin et al. 2004). Fuel coolant
reactions fragment the material in contact with a coolant by
propagating stress waves widening cracks and increasing surface
area leading to rapid cooling rates and explosive thermal
contraction (Heiken & Wohletz 1985).
A submarine eruption is a type of volcanic eruption where lava
erupts under an ocean. Most of the Earth's volcanic eruptions are
submarine eruptions, but few have been documented because of the
difficulty in monitoring submarine volcanoes. Most submarine
eruptions occur at mid-ocean ridges.
are named because of activity
, or under a glacier
. They can cause dangerous floods
, and create
and pillow lava
. Only five of these types of
eruptions have occurred in the present day.
the British Antarctic
Survey (BAS) scientists led by Hugh Corr and David Vaughan
reported (in the journal Nature
Geoscience) that a volcano erupted under
Antarctica ice sheet 2,200 years ago.
this was the biggest eruption in Antarctica in the last 10,000
years. The volcanic ash was identified through a
airborne radar survey, which found an
ash layer buried under later snowfalls in the Hudson
Mountains, close to Pine Island Glacier.
) are driven by explosive expanding steam
resulting from cold ground or surface water coming into contact
with hot rock or magma. The distinguishing feature of phreatic
explosions is that they only blast out fragments of pre-existing
solid rock from the volcanic conduit; no new magma is erupted.
activity is generally weak, but has been known to be strong, such
as the 1965 eruption of Taal Volcano, Philippines, and the 1975-1976 activity at La Soufrière, Guadeloupe (Lesser
Volcanoes do not always erupt vertically from a single crater near
their peak; some volcanoes exhibit lateral and fissure eruptions.
Laki fissure and the Reykjanes crater row in Iceland are examples.
Diagrams of eruption types
eruptionImage:Phreatic Eruption-numbers.svg|Phreatic eruption
Ten deadliest volcanic eruptions
||Mount Tambora (see also Year
Without a Summer)
May 7 or May 8,
||Nevado del Ruiz
August 24th 79
Killed about 25% of the population (33% were killed about 70 years
before by smallpox)
June 8, 1783|
May 19, 1919|
supervolcanic eruption at Lake Toba around 74,000 years ago could have wiped out as
much as 99% of the global human population, reducing the population
from a possible 60 million to less than 10 thousand; see Toba catastrophe theory.
However, this theory is not widely accepted because the evidence is
disputed, and there have been, for instance, no remains found. The
eruption is not listed here as it was pre-historic and outside the
scope of this article. Also, the Thera eruption in the Aegean
Sea between 1550 and 1650 B.C. may have caused a large
number of deaths throughout the region, from Crete to Egypt.
Caldera, Yellowstone Caldera, and Supervolcanoes.
- Island Building Events
- Ancient Antarctic eruption noted, BBC NEWS, 20
- Heiken, G. & Wohletz, K. 1985. Volcanic Ash. University of
California Press, Berkeley.
- Starostin, A. B., Barmin, A. A. & Melnik, O.E. 2005. A
transient model for explosive and phreatomagmatic eruptions.
Journal of Volcanology and Geothermal Research, 143, 133-151.
- Pyle, D. M. 1989. The thickness, volume and grainsize of tephra
fall deposits. Bulletin of Volcanology, 51, 1-15.
- Riley, C. M., Rose, W. I. & Bluth, G.J.S. 2003. Quantitive
shape measurements of distal volcanic ash. Journal of Geophysical
Research, 108, B10, 2504.