Download Volcanoes lesson 2

Volcanoes
Chapter 3
Section 2
Volcanic Activity
Characteristics of Magma
Lava begins as magma in the mantle
How does magma rise?
Magma is less dense than the
surrounding solid material.
Magma flows upward into any cracks
in the rock above.
Magma rises until it reaches the
surface.
Characteristics of Magma
What does the force of a volcanic eruption
depend upon?
The amount of gas dissolved in the
magma
The thickness or thinness of the
magma – thicker magma flows more
slowly
The temperature of the magma - the
hotter the magma the more fluid it is
The silica (material formed from
oxygen and silicon) content of magma
– the more silica the thicker the magma
Characteristics of Magma
What is formed by magma?
Magma that is high in silica forms:
Rhyolite, which has the same
composition as granite
Obsidian forms when lava cools
quickly
Pumice forms when gas
bubbles are trapped in cooling
lava
Magma that is low in silica forms:
basalt
Stages of a Volcano
Active – a volcano that is erupting or has shown
signs that it may erupt in the near future.
Stages of a Volcano
Largest active volcano - Mauna Loa in Hawaii rises
13,677 feet above sea level, it last erupted in 1984.
Stages of a Volcano
Dormant – a volcano that will awaken
sometime in the future and erupt (may be
thousands of years later).
Mount Rainier at
4,393 meters
(14,410 feet) is the
highest peak in the
Cascade Range.
Stages of a Volcano
Extinct – a volcano that is unlikely to erupt
again.
Crater Lake was formed after the
collapse of an ancient volcano,
posthumously named Mount
Mazama. This volcano violently
erupted approximately 7700
years ago. The basin was formed
after the top 5000 feet of the
volcano collapsed. Subsequent
lava flows sealed the bottom,
allowing the caldera to fill with
approximately 4.6 trillion gallons
of water from rainfall and snow
melt, to create the seventh
deepest lake in the world at
1,932 feet.
Other Types of Volcanic
Activity
Hot spring – forms when groundwater heated
by a nearby body of magma rises to the
surface and collects in a natural pool.
Little Hot Creek –
temperatures in this
pool can reach 80 C
and it is lined with
minerals and algae.
Other Types of Volcanic
Activity
Geyser – forms when rising hot water and
steam becomes trapped underground in a
narrow crack. As pressure builds the water and
steam will erupt from the ground.
Castle Geyser in
Yellowstone National
Park erupts water and
steam.
Volcano Hazards
Quiet Eruptions – lava flows pour from vents,
setting fire to and then burying everything in
their paths.
Explosive Eruptions – hot burning clouds of
gas burst out as well as cinders and bombs.
Volcanic Ash – can bury entire towns.
Landslides, and avalanches can occur as a
result of a volcanic eruption.
Volcano Hazards
Snow- and ice-capped
volcanoes like Mount St.
Helens are especially
dangerous if they erupt. Much
of the water in Mount St.
Helens' mudflows came from
snow and ice melted by the
heat of the eruption. These
mudflows were as thick as wet
cement and able to carry along
almost anything that they
picked up.
Volcano Webcams
Works Cited
http://shearthscience.wikispaces.com/Pumice-B
http://en.wiktionary.org/wiki/obsidian
http://en.wikipedia.org/wiki/Rhyolite
http://geology.com/rocks/basalt.shtml
http://vulcan.wr.usgs.gov/Glossary/PlateTectonics/Maps/map_plate_tectonics_worl
d.html
http://hvo.wr.usgs.gov/maunaloa/history/4305078_caption.html
http://vulcan.wr.usgs.gov/LivingWith/VolcanicFacts/misc_volcanic_facts.html
http://vulcan.wr.usgs.gov/Volcanoes/CraterLake/Locale/framework.html
http://volcanoes.usgs.gov/lvo/publications/gallery/littlehotcreek.php
http://volcanoes.usgs.gov/images/pglossary/geyser.php
http://egsc.usgs.gov/isb/pubs/teachers-packets/volcanoes/poster/poster.html