Transcript Volcanic Eruptions

Volcanic Eruptions
And Their Erupting Contents
Nonexplosive Eruptions
• Most common type of eruption
• Produce relatively calm flows of lava
• Lava can slowly creep or travel up to 60
km/h
Types of lava
•
•
•
•
Aa
Pahoehoe
Pillow lava
Blocky lava
Aa lava
•
Pours out quickly & forms a brittle crust
•
Crust is torn into jagged pieces as lava
continues to move beneath it.
•
A’a lava flows have a very rough surface
because of their high eruption rates.
•
Named for the painful experience gained by
walking across these jagged pieces if walking
barefoot
A’a-Lava
Pahoehoe
1. Pahoehoe lava flows have a
relatively smooth surface
texture because of their low
eruption rates.
2. Pahoehoe lava flows develop
surface crusts that form thick
plates with ropy and/or gently
undulating surfaces.
Pahoehoe lava sampling
Pillow Lava
1. Pillow lava forms
from underwater
eruptions.
2. “Pillow” lava is socalled because it
forms rounded
lumps that look
like fat pillows, or
the bolster
cushions of a
sofa.
Pillow lava
3. The pillows can form
piles a few to tens of
meters high.
4. Pillow lava flows can be
many hundreds of meters
to kilometers long.
Blocky Lava
• Cool stiff lava that does not travel far from
the erupting vent.
• It cools and form sharp edged chunks.
Explosive (Pyroclastic) eruptions
• Rarer than nonexplosive eruptions
• Very destructive effects
• Clouds of hot debris, ash, and gas rapidly shoot
out of the volcano during an explosive eruption.
• Ash can encircle the globe and stay in the
atmosphere for years.
The Cataclysmic 1991 Eruption of Mount Pinatubo,
Philippines
The second-largest volcanic eruption of this century, and by
far the largest eruption to affect a densely populated area,
occurred at Mount Pinatubo in the Philippines on June 15,
1991. The eruption produced high-speed avalanches of hot
ash and gas, giant mudflows, and a cloud of volcanic ash
hundreds of miles across. The impacts of the eruption
continue to this day.
The Cataclysmic 1991 Eruption of
Mount Pinatubo, Philippines
A huge cloud of volcanic ash and gas rises above
Mount Pinatubo, Philippines, on June 12, 1991.
Three days later, the volcano exploded in the
second-largest volcanic eruption on Earth in this
century. Timely forecasts of this eruption by
scientists from the Philippine Institute of
Volcanology and Seismology and the U.S.
Geological Survey enabled people living near
the volcano to evacuate to safer distances,
saving at least 5,000 lives.
Pyroclastic (Explosive) Eruptions
4 types of pyroclastic material:
1.
2.
3.
4.
Volcanic blocks
Volcanic bombs
Lapilli
Volcanic Ash
Volcanic Blocks
1.
Volcanic blocks
are solidified
rock fragments
greater than 64
mm in diameter.
2.
Blocks
commonly are
ejected during
explosive
eruptions and
consist of older
pieces of the
volcano.
Volcanic Bombs
1. Volcanic bombs are large
pieces of magma that
harden in the air as the
erupt out of a volcano.
2. They can form in a variety
of sizes and shapes.
Lapilli
1. Lapilli means
“little stones” in
Italian.
2. They are tiny
pieces of
magma that
harden before
they hit the
ground.
Volcanic Ash
1. Volcanic ash forms
when gases in stiff
magma expand
rapidly.
2. The walls of the gas
bubbles explode
into tiny glasslike
slivers.
3. Ash makes up most
of a pyroclastic
eruption.
Review
1.
List the 4 types of lava.
2.
This type of lava is very rough with jagged edges.
3.
This type of lava forms from underwater eruptions, looks like
rounded lumps.
4.
This type of lava has a smooth surface and rounded edges.
5.
This type of lava forms sharp edged chunks.
6.
List the four types of pyroclastic material.
7.
These are large blobs of magma that have cooled and hardened as
they flew through the air.
8.
These are tiny pieces of magma that have hardened in the air.
9.
These are solid rock fragments and usually consist of pieces of the
old volcano.
10.
This is formed from when gases in stiff magma expand and explode
into slivers.
Answers
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3.
4.
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10.
A’a, pahoehoe, pillow, blocky
A’a
Pillow
Pahoehoe
Blocky
Blocks, bombs, lapilli, ash
Blocks
Lapilli
Bombs
Ash