Technological Institute of the Philippines
938 Aurora Blvd. Cubao, Quezon City
CE301- Engineering Geology
VOLCANOLOGY
GROUP 4
Anglacer, Adam
Coderes, Melissa
Discaya, Allen Jake
Sebastian, Adrianne
Sunga, Adrian
What is volcanology?
- Volcanology (also spelled vulcanology) is the study of volcanoes, lava, magma, and related
geological, geophysical and geochemical phenomena.
- The term volcanology is derived from the Latin word vulcan. Vulcan was the ancient Roman
God of fire.
Terms related:
•
Lava- molten rock expelled by a volcano during an eruption and the resulting rock after
solidification and cooling.
•
Magma- (from Greek μάγμα, "thick unguent") is a mixture of molten or semi-molten rock,
volatiles and solids that is found beneath the surface of the Earth, and is expected to exist on
other terrestrial planets. Besides molten rock, magma may also contain suspended crystals,
dissolved gas and sometimes gas bubbles.
•
Tectonic plates- pieces of Earth's crust and uppermost mantle, together referred to as the
lithosphere. The plates are around 100 km (62 mi) thick and consist of two principal types of
material: oceanic crust (also called sima from silicon and magnesium) and continental crust (sial
from silicon and aluminum).
Parts of a volcano:
Types of volcanoes in terms of state:
•
Extinct volcanoes- are those volcanoes which have become dead and do not show any signs of
eruption already. Extinct volcanoes are declared extinct, and hence, they will never erupt again.
Some examples of extinct volcanoes include Aconcagua in Argentina, Mount Kenya in Kenya,
Mount Ashitaka in Japan and Mount Buninyong in Australia.
•
Dormant volcanoes- are those volcanoes that have been in the state of sleep or dormancy for a
very long period of time. Commonly, dormant volcanoes are those volcanoes that have not
erupted for at least 2,000 years ago. However, dormant volcanoes are not extinct, and hence,
can erupt at any stage of time.
One of the best examples of a dormant volcano is the Mauna Kea, one of the five volcanoes that
make up the big island of Hawaii.
•
Active volcanoes- unlike extinct volcanoes and dormant volcanoes, active volcanoes are
considered as immediate threats. Active volcanoes are those volcanoes that erupt lava, gases
and/or show seismic activities. An active volcano may have erupted recently, and is always at a
risk of erupting again.
There are large numbers of active volcanoes in the Philippines alone like Taal volcano and Mt.
Pinatubo. But aside from being the most active, Mayon volcano is the most famous tourist attraction
because of its classic conical shape of a stratovolcano.
Types of volcanoes in terms of structure:
•
Cinder Cones-One of the most common types of volcanoes is the ‘Cinder Cones’. A relatively
less-dangerous type of volcano, Cinder cones only grow to about a 1,000 – 1,200 ft. Unlike some
of the other types of volcanoes – namely, shield volcanoes and composite volcanoes – these
cinder cones are usually created from a single opening. The opening of a cinder cone is a coneshaped structure, while the steeps are formed of the erupted, fragmented cinders that fall close
to the chimney/vent.
•
Shield Volcanoes- Another type of volcanoes is the ‘Shield Volcanoes’. Unlike cinder cones,
shield volcanoes can be very, very big in size. However, they are not as much dangerous as it
seems. This is because the eruption of lava out of shield volcanoes is not accompanied by
pyroclastic material. This makes the eruption relatively safer and it keeps the shield volcanoes
safe, too. The structure of shield volcanoes can be understood as tall and broad, but with flat
round shapes around it. In comparison with some of the other types of volcanoes, shield
volcanoes have low slopes.
•
Composite Volcanoes- are also very commonly known as ‘Strato Volcanoes’. Composite
volcanoes are reasonably big and can rise up to 8,000 – 10,000 feet. Moreover, they can range
anywhere from 1 – 10 km in diameter. The nature of composite volcanoes’ eruption is
dangerous and explosive in nature. With a lot of layers of lava and pyroclastic materials
involved, the eruption of composite volcanoes is considered noticeably dangerous.
•
Lava domes- unlike composite and shield volcanoes, lava domes are of significantly smaller
stature. Basically, lava domes are formed when the lava is too viscous to flow to a great
distance, and hence, it continues to pile within. As the lava dome keeps growing, the outer
surface starts to cool and become hardened. When a lava dome is grown to a significant extent,
it shatters the outer surface, which results in spilling loose fragments towards its sides.
Generally, such lava domes are found on the flanks of larger composite volcanoes.
Instruments used in studying volcanoes:







Rock hammer- used for breaking-off samples of igneous rocks for laboratory analysis.
Drill- used to dig into the volcano’s core to collect other samples.
Tiltmeter- used to measure any changes in the angle of volcano’s slope that might indicate
gas build-up.
GPS- used to detect gas build-up that causes change in volcano’s shape.
Spectrometer- used to measure how the gases emitted affect the light.
Seismometer- used to detect small earthquakes in the vicinity.
Thermal camera- to find flows of lava flowing down the mountain and to generate 3D maps
to calculate the likely route of lava flow.
Why do volcanoes erupt?
Volcanoes erupt because of density and pressure. 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. As the
magma rises, bubbles start to form from the gas dissolved in the magma. The gas bubbles exert
tremendous pressure. This pressure helps to bring the magma to the surface and forces it in the air,
sometimes to great heights.
How do volcanoes erupt?
Deep within the Earth it is so hot that some rocks slowly melt and become a thick flowing
substance called magma. Because it is lighter than the solid rock around it, magma rises and collects
in magma chambers. Eventually some of the magma pushes through vents and fissures in the Earth's
surface. A volcanic eruption occurs then magma that has erupted is called lava.
Good and bad effects of volcanic eruption:
Harmful:
1. Death and destruction including loss of human life.
2. Threat to nearby structures and building as heavy ash falls may caused them to collapse.
3. Ash suffocation of human and animals.
4. Respiratory problems.
5. Pyroclastic flow which is composed of hot gas and ash.
6. When lava cooled down, it will turn into solid rocks which can block roads and may possibly
affect all means of transportation, business and communication.
Beneficial:
1. Volcanoes help in cooling-off the earth by removing heat from its interior.
2. Lava and ash are nutrient-rich elements which make a very fertile farmland.
3. Volcanoes are a good source of geothermal power, provided there is a geothermal power plant
to generate such energy.
4. Volcanoes create remarkable scenery that is great for tourism.
5. Volcanic deposits can be used as building materials.
6. Pumice, a volcanic ash, is mostly used as abrasive in soaps and cleaners. Finest grades are used
in silverwares, polishing metals before electroplating and is also great for wood working.