Introduction to Introduction to VolcanologyVolcanology

May 2008May 2008

Chapter 1

ContentContent1.- Volcano.

Concept. Origin. Parts. Earthquakes, tsunamis and volcanoes. Volcanology.

2.-Volcanism. Concept. Types.Heat source. Isotopes. Accretional heating. Tidal heating. Core formation. Meteorits.

VOLCANOVOLCANO

VolcanoVolcano

An opening in the earth’s surface through which lava, hot gases, and

rock fragments erupt.

Origin of VolcanosOrigin of Volcanos1.- Magma 50-100 miles below the earth’s surface slowly begins to rise to the

surface.

2.- As the magma rises it melts gaps in the surrounding rock.

3.- As more magma rises a large reservoir forms as close as 2 miles below the surface (magma chamber)

4.- Pressure from the surrounding rock causes the magma to blast or melt a conduit (channel) to the surface where magma erupts onto the surface through a vent (opening).

5.- The magma, now called lava, builds up at the vent forming a volcano.

6.- Often the volcano sides will be higher than the vent forming a depression called a crater

VolcanoVolcano

Mount Saint Helen Eruption, May 18th 1980

Magma chamber

conduitmantle

Parasitic Cone

Ash Cloud/Gases

Vent

Lava Flow

Crater

Parts of a VolcanoParts of a Volcano

““Ring of Fire”Ring of Fire”

Volcanic arcs and oceanic trenches partly encircling the Pacific Basin form the so-called , a zone of frequent earthquakes and volcanic eruptions.

Volcanoes and earthquakesThe distribution of earthquakes provides information about magma pathways and the structure of volcanoes and they

also can have a lot to do with generating tsunami. Any time that you can somehow displace a large amount of ocean water you generate a large wave or group of waves that

goes rushing across the ocean at great speed.

VolcanologyVolcanology

Volcanology (also spelled vulcanology) is the branch of

geology that studies volcanoes, lava, magma and related geological phenomena.

VOLCANISMVOLCANISM

VolcanismVolcanism

Volcanism is part of the process of bringing material from the deep interior of a planet and spilling it forth on the surface. In many

cases, eruptions build up a piled of material, a

mountain what is called volcano.

Origin of VolcanismOrigin of Volcanism

There are four types of volcanism:- Related with midocean ridges.- Related with subduction zones - Related with Hotspots- Related with flood volcanism

Heat SourceHeat Source

The heat from a volcano comes from deep within the earth.

Many miles underground, the earth is hot. Rocks beneath the earth are so hot they turn into

a liquid called lava.

When a volcano erupts, the steam and ash is caused by lava that is forcing its way toward the surface of the

earth.

IsotopesIsotopes

Isotopes are any of the different forms of an element each having different atomic

mass (mass number). Isotopes of an element have nuclei with the same number of protons (the same atomic

number) but different numbers of neutrons.

Therefore, isotopes have different mass numbers, which give the total number of nucleons—the number of protons plus

neutrons.

Hydrogen

Deiterium

Tritium

UU235 – 235 – UU238238 U235 is an isotope of uranium that differs from the element's

other common isotope, uranium-238, by its ability to cause a

rapidly expanding fission chain reaction, i.e., it is fissile. It is the only fissile isotope found in any economic quantity in nature. It

was discovered in 1935 by Arthur Jeffrey.

U238 is the most common isotope of uranium found in nature. In a nuclear reactor, it can be used to breed plutonium-239, which itself can be used in a nuclear weapon or as a

reactor fuel source.

ThTh232232 – K – K4040Thorium is found in small

amounts in most rocks and soils. Th232 is used in combination with a fissile nuclide as a fuel

source in types of nuclear reactors known as breeder

reactors.  Breeder reactors are able to continually generate new fuel as fuel is being consumed.   

K40, which has a radioactive half-life of about 1.2 billion years, could be an

important source of heat in the Earth’s core but this has never been

unambiguously confirmed in an experiment.

Accretional HeatingAccretional HeatingThe heating of bodies orbiting a star due to bombardment by smaller objects . Accretional heating in forming planets

results from the transfer of kinetic energy of objects striking the proto - planet surface.

By accounting for all energy transfer for every cratering event it is

theoretically possible to determine the thermal state of newly- formed

planets

Tidal HeatingTidal Heating

In some other planents is too small to have left over accretional heat, and radioactive decay could not generate the

tremendous energy required to power all of

the volcanic activity that exists on the

moon.

Core FormationCore FormationExtensive melting of the earth as a result of giant impacts,

accretion, or the presence of a dense blanketing atmosphere is thought to have led to the formation of the core. Collision between a planet- sized body and the earth

may have also produced the moon.

Near the end of accretion, core formation evidently ceased as upper mantle conditions became oxidizing. The accumulation of the oceans is a

consequence of the change to oxidizing conditions.

MeteoritsMeteorits

Chondrites are stony meteorites that have

not been modified due to melting or

differentiation of the parent body. They

formed when various types of dust and small

grains that were present in the early solar

system accreted to form primitive asteroids