Shield volcanoes are the largest
volcanoes on earth.They are built
by basalt lava flows and have gentle
slopes that move from the top of the
volcano to the bottom.
Lava domes are built by a kind
of viscous lava.Viscous lava is a thick
mixture that can not flow quickly, so the
lava cools too quickly to really move any
distance from the eruption.
Strato volcanoCinder ConeVolcano
Cinder cones are steep sided hills made up
of fragments from a volcanic eruption.The
fragments that form these cinder cones are blown
down wind from an eruption from a stratovolcano.
You can see the stratovolcano that formed this
cinder cone in the background.
Strato volcanoes are shaped like a cone, but
have very steep sides.They are formed during
violent eruptions by lava flows , tephra,
and pyroclastic flows.They are formed by
several vents that lead from deep underground
and may form cinder cones nearby.
Mud volcano is A conical accumulation of
variable admixtures of sand and rock fragments,
the whole resulting from eruption of wet mud
and impelled upward by fluid or gas pressure.
Also known as hervidero; macaluba.
A caldera is a cauldron-like volcanic feature
usually formed by the collapse of land following
a volcanic eruption, such as the one
atYellowstone National Park in the US.They are
sometimes confused with volcanic craters
Olympus Mons (Latin for Mount Olympus) is a large
volcanic mountain on the planet Mars. At a height of almost
22 km (14 mi), it is one of the tallest mountains in the
Solar System, three times as tall as Mount Everest and more
than twice the height of Mauna Kea the tallest mountain on
Earth. Olympus Mons is the youngest of the large volcanoes
on Mars, having formed during Mars' Amazonian Period.
Olympus Mons had been known to astronomers since the
late 19th century as the albedo feature Nix Olympica (Latin
for "Snows of Olympus"). Its mountainous nature was
suspected well before space probes confirmed its identity
as a mountain
About 250 million years ago, about 95 percent of life was wiped out in the sea and 70 percent on
land. Researchers at the University of Calgary believe they have discovered evidence to support
massivevolcanic eruptions burnt significant volumes of coal, producing ash clouds that had broad
impact on global oceans.
"This could literally be the smoking gun that explains the latestPermian extinction," says Dr. Steve
Grasby, adjunct professor in the U of C's geoscience department and research scientist at Natural
Grasby and colleagues discovered layers of coal ash in rocks from the extinction boundary in
Canada's High Arctic that give the first direct proof to support this and have published their findings
in Nature Geoscience. Unlike the end of the dinosaurs, 65 million years ago-where there is
widespread belief that the impact of a meteorite was at least the partial cause-it is unclear what
caused the late Permian extinction. Previous researchers have suggested massive volcanic
eruptions through coal beds in Siberia would generate significant greenhouse gases causing run
away global warming.
How can a volcano create lightning? Why is volcanic lightning often contained within or in close
proximity to the ash plume? What types of eruptions are most conducive for the creation of
volcanic lightning? These are all good questions, and in order to answer them we must first
look at the physics that makes it all possible.
In order for lightning to form there is one key component; a large charge separation between
two masses. If the charge separation becomes big enough it is then able to overpower the air
resistance, create a path of ionized air, and conduct electricity in the form of lightning. The ash
that is to be erupted begins as electro statically neutral rock or rock fragments. Heat and
movement within the volcano is thought to be the first source of particle charging, although the
main process by which ash particles acquire a charge is friction. When an object (in this case
ash) with a neutral charge comes in contact with another object with differrent electro static
qualities, electrons can potentially flow and one of the objects can become charged relative to
the other. Think of skidding your socked feet rapidly across the carpet or rubbing a balloon
quickly against your head. The same type of charge is accumulating within the ash cloud, only
on a much larger scale.
volcanoes can be exciting and fascinating, but also very dangerous. Any kind of volcano
is capable of creating harmful or deadly phenomena, whether during an eruption or a
period of quiescence. Understanding what a volcano can do is the first step in
mitigating volcanic hazards, but it is important to remember that even if scientists
have studied a volcano for decades, they do not necessarily know everything it is
capable of. Volcanoes are natural systems, and always have some element of
Volcanologists are always working to understand how volcanic hazards behave, and what
can be done to avoid them. Here are a few of the more common hazards, and some of the
ways that they are formed and behave. (Please note that this is intended as a source of
basic information only, and should not be treated as a survival guide by those who live
near a volcano. Always listen to the warnings and information issued by your local
volcanologists and civil authorities.)
WHAT IS AN ACTIVE VOLCANO?
THE TERM "ACTIVE VOLCANO" IS USED MAINLY IN REFERENCE TO EARTH'S VOLCANOES.
ACTIVE VOLCANOES ARE ONES THAT ARE CURRENTLY ERUPTING OR THAT HAVE ERUPTED AT
SOME TIME IN HUMAN HISTORY.
THIS DEFINITION WORKS WELL FOR VOLCANOES ON EARTH BECAUSE WE CAN OBSERVE THEM
EASILY. HOWEVER, BEYOND EARTH OUR ABILITIES TO DETECT VOLCANIC ERUPTIONS DID
NOT BEGIN UNTIL THE INVENTION OF POWERFUL TELESCOPES. TODAY A NUMBER OF
TELESCOPES ARE AVAILABLE TO DETECT THESE ERUPTIONS - IF THEY ARE LARGE
ENOUGH. HOWEVER SMALL ERUPTIONS WOULD NOT BE NOTICED AND THERE ARE NOT ENOUGH
TELESCOPES TO WATCH ALL AREAS OF THE SOLAR SYSTEM WHERE A VOLCANIC ACTIVITY
ALTHOUGH ONLY A FEW EXTRATERRESTRIAL ERUPTIONS HAVE BEEN DETECTED, MUCH HAS
BEEN LEARNED ABOUT THEM. PERHAPS THE MOST IMPORTANT DISCOVERY IS THE ONES
THAT HAVE BEEN OBSERVED SO FAR ARE VERY DIFFERENT FROM VOLCANOES THAT OCCUR
ON EARTH. THEY ARE CRYOVOLCANOES.
An eruption begins when pressureon a magmachamber forcesmagmaupthrough the conduitand out
the volcano'svents. When the magmachamber hasbeen completelyfilled,the type of eruption partly
dependson the amountof gasesand silica in themagma. The amountof silicadetermines
how sticky (levelofviscosity)the magmais and waterprovides theexplosivepotentialofsteam.Obstacles
also influencethe type of eruption. When the pipe isblockedby a stoppleor an accumulationof pumice,
the pressurein thepipewill buildup veryhigh resulting in an explosion.
When magmareachesearth's surfaceit is called lava. Itmay pourout in gentle streamscalled lava
flowsor eruptviolentlyinto the air. Rocksrippedloose from the inside ofthe volcanoor torn apart by
the gas may be shot into the air with the lava. Theserocksblown out of a volcanoare
calledpyroclasticrocks. The rockfragmentsfall backto earth in many differentshapesand
sizes: Volcanicactivity is classified byhow often a volcanoerupts. A volcanomay
be active, intermittent, dormant,or extinct. Activevolcanoes
erupt constantly. Intermittentvolcanoeseruptfairly regularly. Dormant volcanoesare inactive,but not
long enoughto determinewhetherthey will eruptagain or not. Extinct volcanoes havebeen inactivesince
the beginning of recorded history.
Lava is molten rock that flows out of a volcano or volcanic vent. Depending on its
composition and temperature, lava can be very fluid or very sticky (viscous). Fluid
flows are hotter and move the fastest; they can form streams or rivers, or spread out
across the landscape in lobes. Viscous flows are cooler and travel shorter distances,
and can sometimes build up into lava domes or plugs; collapses of flow fronts or domes
can form pyroclastic density currents (discussed later).
Most lava flows can be easily avoided by a person on foot, since they don't move much
faster than walking speed, but a lava flow usually cannot be stopped or diverted.
Because lava flows are extremely hot - between 1,000-2,000°C (1,800 - 3,600° F) - they
can cause severe burns and often burn down vegetation and structures. Lava flowing from
a vent also creates enormous amounts of pressure, which can crush or bury whatever
survives being burned.
volcano is a geological landform usually generated by the eruption through a vent in a
planet's surface of magma, molten rock welling up from the planet's interior. Volcanoes
of various types are found on other planets and their moons as well as on earth. Roughly
defined, a volcano consists of a magma chamber, pipes and vents. The magma chamber is
where magma from deep within the planet pools, while pipes are channels that lead to
surface vents, openings in the volcano's surface through which lava is ejected during an
Though the common perception of a volcano as a mountain spewing lava and poisonous gases
from a crater in its top is not wrong per se, the features of volcanoes are much more
complicated and vary from volcano to volcano depending on a number of factors. Some
volcanoes even have rugged peaks formed by lava domes rather than a summit crater,
whereas yet others present landscape features such as massive plateaus. Vents that issue
volcanic material (lava, which is what magma is called once it has broken the surface,
and ash) and gases (mainly steam and magmatic gases) can be located anywhere on the
landform. Many of these vents give rise to smaller cones such as Pu‘u ‘Ō‘ō on a flank of
Volcanic ash consists of powder-size to sand-size particles of igneous rock
material that have been blown into the air by an erupting volcano .The
term is used for the material while it is in the air, after it falls to the ground
and sometimes after it has been transformed into rock.The terms
"volcanic dust" and "volcanic ash" are both used for the same material,
however "volcanic dust" is more appropriately used for powder-size
material. Ash deposited on the ground after an eruption is known as
ashfall deposit. Significant accumulations of ashfall can lead to the
immediate destruction of most of the local ecosystem, as well the
collapse of roofs on man-made structures.Over time, ashfall can lead to
the creation of fertile soils.
About 10 miles off the Santa Barbara coast, at the bottom of the Santa
Barbara Channel, a series of impressive landmarks rise from the sea floor.
They've been there for 40,000 years, but have remained hidden in the
murky depths of the Pacific Ocean--until now.
They're called asphalt volcanoes.
Scientists funded by the National Science Foundation (NSF) and affiliated
with the University of California at Santa Barbara (UCSB), the Woods Hole
Oceanographic Institution (WHOI), University of California at Davis,
University of Sydney and University of Rhode Island, have identified the
series of unusual volcanoes.
How They Avoided Discovery
The largest of these undersea Ice Age domes lies at a depth of 700 feet
(220 meters), too deep for scuba diving, which explains why the volcanoes
have never before been spotted by humans, says Don Rice, director of
NSF'sChemical Oceanography Program, which funded the research.
"They're larger than a football-field-long and as tall as a six-story building,"
says DavidValentine, a geoscientist at UCSB and the lead author of a paper
published on-line this week in the journal Nature Geoscience. "They're
massive features, and are made completely out of asphalt."
Valentine and colleagues first viewed the volcanoes during a 2007 dive on
the research submersibleAlvin.Valentine credits Ed Keller, an earth
scientist at UCSB, with guiding him and colleagues to the site.
ArenalVolcano, the youngest stratovolcano in Costa Rica, is one
of the most active volcanoes in that country and in the world. It
has been producing lava and pyroclastic flows almost
continuously since 1968; this activity has been both a danger to
people living near the volcano and a draw for thousands of
tourists over the years. Located on the eastern shore of Lake
Arenal in northwestern Costa Rica,Volcan Arenal was thought to
be extinct prior to the eruptions of 1968, although it is now
known that eruptions have occurred on and off for the last 7,000
The volcanic arc of Costa Rica, where Arenal is located, is a
chain of mountains resulting from the subduction of the
Cocos tectonic plate under the Caribbean Plate. Costa Rica is
part of the Central American isthmus, which connects the
North and South American continentsVolcanoes are mostly
confined to a NW-SE trending strip in the northern part of
Costa Rica because the Cocos plate subducts at a very steep
angle there, and because the Cocos Ridge disrupts normal
subduction to the southeast. Arenal is located northwest of
the Chato volcanic complex, which last erupted about 4,000
ArenalVolcano: PlateTectonic Setting
Geologists identify the three major rock types as igneous, sedimentary, and
metamorphic. Each specific rock begins due to the Earth's mantle melting and
forcing magma to the ground surface.The process of nature transforms the
molten rock into igneous, sedimentary, and then metamorphic. (2004, Rock
Cycle).The Rock Cycle
Igneous rocks may be formed due to the cooling of molten rock released by
volcanic magma above or below the Earth's surface.Volcanic igneous rocks
begin to form when the temperature of molten rock is cooled quickly after an
eruption above the surface. Plutonic igneous rocks are formed beneath the
surface after the molten rock slowly cools and solidifies. (2004, Rock Cycle).
Metamorphic rocks may be formed due to chemical and physical
changes of igneous or sedimentary rocks. Igneous and
sedimentary rocks endure high levels of pressure, heat, and force
which produce the metamorphic rock. Igneous, sedimentary, or
metamorphic rocks can be heated to such a degree in which they
are melted and repeat the rock cycle. (2000, Fichter).
Sedimentary rocks are a result of igneous rocks enduring
weathering, erosion, and lithification. Igneous rocks are
exposed to nature's process of transporting small particles
of the rocks and depositing them as sediments. Sediments
endure the process of lithification which compacts and
cements the small particles of igneous rocks.The
hardened particles are then formed into sedimentary
rocks. (2005, Rocks).
Hawaii is a very popular vacation spot and tourist attraction.The island
is apart of the United States and is surrounded by five volcanoes.
Kohala, Mauna Kea, Hualalai, Mauna Loa, and Kilauea are the
volcanoes that make up the big island of Hawaii. One volcano is
considered dormant, one extinct, and the remaining three are said to
be active. (2007, Fisher).Visiting Hawaii can be very exciting, especially
if you wish to see volcanoes. However, it's nearly impossible to see the
entire rock cycle process.The Earth's mantle pushes melting magma
towards the surface and erupts through a volcano.
The magma is spread across land which is viewable to
people on the island of Hawaii.The molten rock would be
cooled and hardened into igneous rock.This process may
also take place underground which would not be viewable to
tourists and residents of Hawaii.Viewing volcanic activity is
an everyday event for residents but can be rather scary for
tourists if they don't know what to expect! Sedimentary and
metamorphic rocks would not be able to be seen
immediately after an eruption. Often the process of their
transitions into rocks is below the Earth's surface. (2004,
The Philippine Institute ofVolcanology and
Seismology (Filipino: Suriang Pilipino ng Bulkanolohiya at
Sesmolohiya, abbreviated as PHIVOLCS) is a Philippine national
institution dedicated to provide information on the activities
of volcanoes, earthquakes and tsunamis, as well as other
specialized information and services primarily for the protection
of life and property and in support of economic, productivity and
sustainable development. It is one of the service agencies of
the Department of Science andTechnology.
Phivolcs monitors volcano, earthquake, and tsunami activity,
and issues warnings as necessary. It is mandated to mitigate
disasters that may arise from such volcanic
eruptions, earthquakes, tsunami and other
related geotectonic phenomena.
The predecessor to PHILVOCS, the Commission onVolcanology (COMVOL)
was created on June 20, 1952 by RepublicAct no. 766 after the disastrous
eruption of Hibok-HibokVolcano in 1952.
Under Executive Order no. 784 of March 17, 1982, the umbrella department of
COMVOL, the National Science Development Board (NSDB) was reorganized
into the National Science andTechnology Authority (NSTA), and COMVOL
was restructured to become the Philippine Institute of Volcanology or
The seismological division of the PAGASA, the successor to the Philippine
Weather Bureau created in 1907, was transferred to PHILVOLC on September
17, 1984, renaming the institute as the Philippines Institute of Volcanology
and Seismology or PHILVOCS. NSTA, the umbrella department for PHILVOCS
and PAG-ASA became the Department of Science andTechnology (DOST) in
PHILVOCS was headed by Raymundo Punongbayan from 1982 to 2003, and
it is currently headed by Renato U. Solidum Jr. from 2003 to the present.