volcanic activity
TRANSCRIPT
Volcan c Act v ty
Classification of Volcanic Activity
1. Active- a volcano that is erupting or has repeatedly erupted in
a short period of time2. Dormant- a volcano that has not
erupted for a considerable length of time
3. Extinct-a volcano that shows no any evidence of erupting again
Classification of Volcanic Eruption
Type of eruption
MeaningReaction of
heat to water or ice
Magmatic Eruption
Eruption-produces juvenile clasts
during explosive decompression
from gas release
Thermal Expansion
Phreatomagmatic eruption
characterized by an explosive
water-magma interaction
through which large amounts of
steam and magmatic gases
are released
Thermal Contraction
Types of Volcanic Eruption
Specific type
UnificationDistinguished
featuresDisplayed
in/byHawaiian Magmatic Generally basaltic
Low level eruption Effusive eruption/fire fountain Column generally less than 500
m Associated with a hotspot Fluid lava flows Result in vast gentle volcanoes
Kilauea, Hawaii
Mauna Loa volcano in 1950
Lava lake Magmatic • Rare cases• Very fluid lava• Weak pyroclastic production
Mauna Ulu, Lava Lake
Erta Ale, Ethiopia
Strombolian Magmatic Basaltic magma More viscous than Hawaiian Intermittent explosions No sustained column Ejecta to heights of a few
hundred meters Minutes of pause between
bursts
Stromboli, Sicily
Paricutin 1943-1952
Mt. Erebus, Antartica
Types of Volcanic Eruption
Specific type
UnificationDistinguished
featuresDisplayed
in/byVulcanian Magmatic Similar to hydrovolcanic
activity Begins with violent noisy
explosion Ejects new lava fragment that
do not take on a rounded shape during their flight through the air
Highly viscous fragmented magma
Clouds rise to 10-20 km Wide dispersal of tephra Can last, with long intervals of
repose, for several millenia
Vulcano, Sicily
Sakurajima in Japan (ongoing) and Irazu in Costa Rica (1965)
Plinian Magmatic Rare events (2-3 in century) Most explosive and powerful Highly evolved magma with
abundant pumice Statospheric eruption columns Huge volumes and large mass
flux
Vesuvius, 79 CE
Mt. Pinatubo 1991
Types of Volcanic EruptionSpecific
typeUnification Distinguished features
Displayed in/by
Subplinian Magmatic High eruptive plumes up to 30 km
Eruption happens after long years of dormancy
Sustained column Generally dacite to rhyolite
composition Continuous sheet of tephra Pumice is common Less fragmented than Vulcanian
products Discrete explosions lasting
seconds to few minutes
Vesuvius, 1822
Phreato-plinian
Phreato-magmatic
No historic eruptions of this type High eruptive column Extremely fine tephra Wide dispersal of deposit
none
Types of Volcanic EruptionSpecific
typeUnification Distinguished features
Displayed in/by
Surtseyan/ Hydro-volcanic
Phreato-magmatic
Rapid small explosion Viscous, basaltic Column less than 500 m Associated with surge clouds Highly fragmented material Commonly within a standing
water body
Surtsey, Iceland
Fire Island, Alaska, USA 1796
Taal Volcano, Batangas, Philippines (last eruption was in 1977)
Subglacial
Phreato-magmatic
No eruptive column. Some ash on the surface of ice sheets
Only surface effect is a ‘’sag’’ in the glacier
Melted ice, fragmented lava and water flood out
Iceland
Process involved in Volcanic Eruption
Volcanic Process- refers to the eruptive and noneruptive activities
that take a place on a volcano
Volcanic activities results if:
1. Confining pressure decreases as a result of decompression from the magma rising from a higher pressure point to a lower pressure point
2. Vapor pressure increases because the magma cools which initiates a crystallization process that enriches the magma content.
Volcanic Materials Brief Description Illustration
Andesite a dark grey volcanic rock
Basalt
a dense dark grey fine-grained igneous
rock that is composed chiefly of plagioclase
feldspar and pyroxene
Dacitea grey volcanic rock
containing plagioclase and quartz and other crystalline minerals
Diorite a granular crystalline intrusive rock
Different volcanic materials
Volcanic Materials Brief Description Illustration
Gabbro one of a family of granular intrusive rocks
Granodioritean intrusive igneous rock
similar to granite, but containing more plagioclase
than potassium feldspar
Obsidianacid or granitic glass formed by the rapid cooling of lava
without crystallization; usually dark, but transparent
in thin pieces
Pegmatitea form of igneous rock consisting of extremely
coarse granite resulting from the crystallization of magma
rich in rare elements
Different volcanic materials
Volcanic Materials Brief Description Illustration
Peridotitea dark coarse-grained
igneous rock consisting principally
of olivine
Plutonic
igneous rock that has solidified beneath the
earth's surface; granite or diorite or
gabbro
Pyroxenite
A heavy, dark igneous rock consisting mostly of pyroxene minerals with smaller amounts
of olivine and hornblende
Scoriathe scum formed by
oxidation at the surface of molten
metals
Different volcanic materials
Volcanic Materials Brief Description Illustration
Rhyolite very acid volcanic rock
Tuffhard volcanic rock
composed of compacted volcanic
ash
Volcanic Gases
Volcanoes emit gases during eruptions. Even when a volcano is not erupting,
cracks in the ground allow gases to reach the surface
through small openings called fumaroles
Different volcanic materials
Thank you for listening!
Prepared By: Julius Cagampang