Download Explosive eruptions

What is a volcano?
• A weak spot
in the crust
where magma
has come to
the surface.
http://alaskadestination.com/alaska-volcano-images/
What is volcanism?
• Any phenomena
associated with
volcanic activity.
• What volcanic
phenomena have
you heard of?
What are some of the things that can
happen during an explosive eruption ?
• Explosion breaks lava
into fragments of
different sizes.
a. volcanic ash
b. cinders
c. bombs
http://www.gc.maricopa.edu/earthsci/imagearchive/b
ombs.htm
• Pyroclastic flow: a
mixture of hot gases,
ash, cinders, and
bombs.
http://www.volcano.si.edu/volcanoes/region15/peru/ubinas/3110ubi7.jpg
What is pahoehoe?
• Lava that flows
easily and
hardens into a
rippled surface.
http://seismo.berkeley.edu/~manga/EPS214/rope.jpg
What is A’a?
• Flows slowly
and hardens
into rough
chunks.
http://www.decadevolcano.net/photos/keywords/a_a_lava.htm
http://www.livingwilderness.com/hawaii/hawaii-pahoehoe-flow.html
http://volcanoes.usgs.gov/hazards/lava/index.php
http://www.earlham.edu/~bestan/Graphics/aa1.jpg
http://stevekluge.com/geoscience/images/
How many active volcanoes are there?
• There are about 600 on land and more under
the ocean where it is hard for scientists to
observe or map them.
What causes a volcano to erupt?
• Dissolved gases are trapped in magma. As the
magma rises, the pressure decreases, and the gases
expand causing bubbles that increase in size as they
rise to the top. The bubbles push the magma from
the chamber into the pipe until it comes out a vent.
What is a quiet eruption?
• Quiet eruptions:
Gases in thin
magma bubbles
out gently.
• Produce both
pahoehoe and
a’a.
• Ex: Hawaiian
Islands
What is an explosive eruption?
• Explosive eruptions:
thick magma plugs
volcano’s pipe like a
cork.
• Ex: Mt. St. Helens
What is the life cycle of a volcano?
•
•
•
Active: one that is
erupting or
showing signs of
erupting
Dormant:
scientists expect
eruption in the
future
Extinct: unlikely to
erupt again.
http://maps.unomaha.edu/Peterson/funda/Pictures/Japan-2/Japan_files/image001.jpg
Mt Fuji in Japan
What kind of landforms are
made by volcanoes?
Diamond Head, Honolulu, HI
Diamond Head is Oahu's largest tuff cone formed over 100,000 years ago by an active bubbling
volcano. Nineteenth century British sailors nicknamed the crater Diamond Head when they mistook
the calcite crystals for diamonds. A well-graded trail leads you up the 760-feet summit to a World War
II bunker with a bird's eye view of Honolulu. (http://commons.wikimedia.org/wiki/File:Diamond-HeadHawaii-Nov-2001.jpg)
Mauna Kea is a shield volcano.
http://cimss.ssec.wisc.edu/sage/geology/lesson3/concepts.html
Lava Pillow
Lava Tube, Vocano National
Park, Hawai’i
http://www.traveltohawaiireviewed.com/bigisland/Attraction/Thurston_Lava_Tube.html
A cinder cone - Sunset Crater, AZ
http://cimss.ssec.wisc.edu/sage/geology/lesson3/concepts.html
Ship Rock, New Mexico is a
volcanic neck or plume.
http://www.scienceclarified.com/landforms/Ocean-Basins-to-Volcanoes/Volcano.html
Great dikes and sills of pink Zoroaster granite
intrude the nearly black, crystalline Vishnu schist,
rising in precipitous, jagged cliffs over thirteen
hundred feet above the Colorado River.
http://www.rockhounds.com/grand_hikes/geology/overview.shtml
Lava plateau in Colorado.
http://www.photos-of-the-year.com/contest/08/potm/showphoto.php?photo=1459
Mount St. Helens in Washington State
is an active composite volcano.
http://www.worldbook.com/wb/Students?content_spotlight/volcanoes/how_kinds
Crater Lake caldera in Oregon.
http://www.swisseduc.ch/stromboli/glossary/caldera-en.html
Half Dome Mountains in
Yosemite national Park, CA
http://www.answers.com/topic/batholith
Hot
Springs
National
Park in
Arkansas
http://www.viewpoints.com/Hot-Springs-National-Park-review-11871
Castle
Geyser in
Yellowstone
National
Park
http://geology.about.com/library/bl/images/blgeyser.htm