Download Roman god of fire, Vulcan

Volcanos
Roman god of fire,
Vulcan
What is a Volcano?
 A volcano is a
mountain that
forms when
magma reaches the
surface of the
Earth.
 Magma rises
because it is less
dense than the
solid rock around
it.
Volcanic activity
• Active - activity in the last few
centuries
Ex: Vesuvius, 79 A.D. (50 times in 2000);
Mt. St. Helens (1980)
Dormant - “quiet” for the last
hundred to thousands of years,
but still have potential to erupt.
Ex: Mt. Rainier
Extinct - No eruption in
historical times, no signs of
erupting again
Volcano Distribution
• Most volcanoes occur in one of three areas:
– Circum-Pacific (i.e. The Ring of Fire) 60%
– Mediterranean 20%
– Spreading centers 10 – 15%
Volcanic Eruptions
• Nonexplosive Eruptions
Lava fountain
Lava flow
• Explosive Eruptions
What is Lava?
-magma that flows onto
the Earth’s surface
What are the parts of a Volcano?
1. VENT- the vent
is the opening
from which lava
flows.
Dust, ash, and rock
particles can also
be thrown out of
the vent!
What are the parts of a Volcano?
2. Crater- the top of
the volcano.
It is a funnel
shaped pit. It is
formed when the
material explodes
out of the vent!
What are the parts of a Volcano?
3. Volcanic coneis the pile of lava,
dust, ashes, and
rock around the
vent.
It can be found in
different shapes!
Volcanic materials
Three types of material expelled from volcanoes:
1. Lava (“the liquid”)
– Molten rock
Pahoehoe lava
Basaltic lava, Low viscosity
Aa lava (pronounced aa-aa)
Basaltic lava, Higher viscosity
Solidifies flowing, Angular pieces
Pillow lavas
Lava extruded underwater, Cools and
contracts, Spherical masses,
Ocean floor
Volcanic materials
2. Ash and pyroclastic material (“the solid”)
Airborne material ejected by a volcano, Classified based on size:
Volcanic ash
<0.06mm to 2mm
Composed of rock, mineral,
and volcanic glass
Bombs
Larger than 64mm
Molten rock solidifies in the air
Shapes vary
Cinders
2 mm to 64 mm
Composition - same as ash
Hazardous when falling
Volcanic materials
Volcanic gases (“the gases”)
Volatiles
H2S – Hydrogen sulfide
H2O – Water vapor
SO2 – Sulfides
CO2 – Carbon dioxide
N2 – Nitrogen
HCl – Hydrochloric Acid
Significance?
Determines violence of an eruption
High gas = violent eruptions
Effects on global climate
CO2 – Greenhouse gas
SO2 – Blocks sunlight
Types of Volcanoes
Shield volcano
Cinder cone volcano
Composite volcano
They are
classified by
how they form.
Volcanic Landforms
• An erupting volcano will produce a number of
distinct landforms including:
A. Volcanic cones
B. Flood basalts
C. Calderas
Volcanic Landforms
Volcanic cones
Shield volcanoes
– Multiple layers of basaltic lava
– Shallow sides due to magma’s low viscosity
– Gentle eruptions
Cinder cones
–
–
–
–
Layered ash and cinders
Smallest volcanic cone
Short, narrow cone, steep sides
Violent eruptions
Composite cones
–
–
–
–
Mauna Loa volcano, HI
El Paricutin
Layered ash, lava, and mud
Steep sides, due to lava’s high viscosity
Tall volcanoes – 1 to 2 miles high
Violent eruptions
St. Helens, WA
Volcanic Landforms
Flood basalts
– Large outpourings of basaltic lava
– Multiple, quiet eruptions
– Lava plateau
Columbia Flood Basalts in WA
Calderas formation:
Volcano rapidly empties its magma chamber,
and support is lost. Overlying material
collapses into magma chamber. Caldera forms.
Type 1:
Explosive calderas
Silica-rich magma has a high viscosity, as a
result gases tend to become trapped at high
pressure within the magma.
Type 2:
Non-explosive calderas
The magma feeding these
volcanoes is basalt which is silica
poor. As a result, the magma is
much less viscous and the magma
chamber is drained by large lava
flows rather than by explosive
events.
Crater Lake, OR
Yellow Stone Caldera
How do volcanologists predict eruptions?
• Measuring Small Quakes
– Before eruption, increase in number & intensity
• Measuring Slope
– Bulges may form with magma (tiltmeter)
• Measuring Volcanic Gases
– Outflow of volcanic gases
• Sulfur dioxide, carbon dioxide
• Measuring Temperature from Orbit
– Measure changes in temperature over time