Download volcanism

Read this
on-line
USGS
publication
at the URL
http://pubs.usgs.gov/gip/volc
Volcanoes of the World
http://www.volcano.si.edu/gvp/volcano/index.htm#regions
Volcanism occurs ...
at the plate margins ...
at divergent boundaries, as the sea floor spreads,
e.g., the spreading submarine ridges and rises; and
at the subducted margins of convergent plate
boundaries ...
when the oceanic edge of one plate collides against the
oceanic edge of another plate, so forming an island arc,
e.g., the Sunda Arc, the Philippines, or
when the oceanic edge of one plate collides against the
continental edge of another plate, e.g., the Cascade Range
volcanism.
at the hot-spots or mantle-plumes, as the HawaiiEmperor chain, Iceland, Azores, Yellowstone etc.,
and
as the flood basalts or Large Igneous Provinces,
e.g., CRB, Deccan, Parana, Siberian Traps etc.
Sea floor spread by
intermittant volcanism at the
mid-ocean ridge (top left)
results in the recording by
subsequent lavas of the geomagnetic polarity reversals
(left bottom) and the resulting
marine magnetic anomalies
can be mapped by the
magnetometers towed by
ships (bottom right).
Map showing the
Mid-Atlantic
Ridge splitting
Iceland and
separating the
North American
and Eurasian
Plates. The map
also shows
Reykjavik, the
capital of
Iceland, the
Thingvellir area,
and the locations
of some of
Iceland's active
volcanoes (red
triangles),
including Krafla.
The Mid-Atlantic
Ridge, which splits
nearly the entire
Atlantic Ocean
north to south, is
probably the bestknown and moststudied example of
a divergent-plate
boundary.
Lava fountains (5p;10 m high)
spouting from
eruptive fissures
during the October
1980 eruption of
Krafla Volcano.
View of the first hightemperature vent (380 °C)
ever seen by scientists
during a dive of the deepsea submersible Alvin on
the East Pacific Rise
(latitude 21° north) in
1979. Such geothermal
vents--called smokers
because they resemble
chimneys--spew dark,
mineral-rich, fluids
heated by contact with the
newly formed, still-hot
oceanic crust. This
photograph shows a
black smoker, but
smokers can also be
white, grey, or clear
depending on the
material being ejected.
The deep-sea hot-spring environment
supports abundant and bizarre sea life,
including tube worms, crabs, giant clams.
This hot-spring "neighborhood" is at 13°
N along the East Pacific Rise.
Plate boundaries can be either active, i.e.,
divergent versus or convergent, or passive
(transform)
Volcanism
occurs at the subducted
margins that form ...
either by the
convergence of oceanic
edges of plates
or by the convergence of
continental edge of one plate and the oceanic edge of the
other.
A convergent plate boundary,
e.g., the convergence of Nazca
and South American plates
Juan de Fuca ridge and
the associated plates
and plate boundaries
off the Pacific Northeast and Canada. Note
that the Cascadia
subduction zone is also
called the “Filled
Trench”, as this trench
got filled by sediments
carried by the huge
runoff from land that
has characterized this
region particularly
since the Last Ice Age.
Nintyeast
Ridge
The Hawaii-Emperor seamounts have evolved over the past
~65 Ma as the Pacific plate traversed a fixed mantle plume.
(http://www.colorado.edu/geography/cartpro/cartography2/spring2001/campbell/final/anime_pg.html)
Archaea Habitats: Rotorua, New Zealand
For information on the LIPs on the internet, try
http://www.ig.utexas.edu/research/projects/lips/lips.html
Also visit the USGS volcanoe sites, starting with
http://volcanoes.usgs.gov/ and the links provided
there.
Deccan traps, the ~106 km3 flood
basalt province in peninsular India,
extruded at or about the K/T boundary.
Photograph by Lazlo Keszthelyi
http://volcano.und.nodak.edu/vwdocs/Parks/hawaii/recent_events/dinosaurs.jpg
http://www.etl.noaa.gov/review/aq/post/e.html
Mt. Pinatubo: June 13, 1991
El Chichon, March 1982
Satellites tracked the spread of airborne sulfuric
acid mist formed by SO2 from the 1991 eruption of
Mt. Pinatubo, Phillippines
5/20-6/6/91 (before eruption)
7/4-7/10/91 (after circulating the earth)
The two
volcanoes
had
remarkably
similar build-up
El Chicon
Mt. Pinatubo
Aerosol loading before and after Mt. Pinatubo's eruption. Note the
simultaneous increase in tropospheric and stratospheric loading.
Tropopause folds seasonally purge lower sratospheric
material into the troposhpere.
The ratio between (separation of) ruby and CO2 backscatter
coefficients indicates the median size of sulfuric acid aerosol
particles.
But their
decay phases
were notably
different
El Chicon
Mt. Pinatubo
Mt. Pinatubo
El Chicon
Conclusion
Multi-year, multi-wavelength lidar studies of
two major volcanic events reveal details of
buildup and decay that are important for
proper climatic modeling of such events.
Over the United States, build-up from these
two tropical volcanoes appears to be similar
but decay is dissimilar. Simultaeously, both
the troposphere and the stratosphere are
affected by such eruptions, a heretofore
unknown result.
http://www.etl.noaa.gov/review/aq/post/c.html
Pinatubo eruption, June 15, 1991.
This image was collected during the beginning of the 3-hourlong climactic eruption. The yellow X is the approximate
location of the vent and the red outline is the coastline of the
northern Philippines. (R. Holasek)
http://geont1.lanl.gov/HEIKEN/one/atmosphere.htm
Ice contact and Subglacial Volcanism
http://perseus.geology.ubc.ca/projects/subglacial/
The worldwide distribution of
sub-glacial volcanic deposits
 Iceland
 Alaska, British Columbia,
Yukon and the Cascades
 Antarctica
 Andes
 Hawaii
Lake Nyos,
Cameroon
Catastrophe at
Lake Nyos, Cameroon
On August 21, 1986, a massive
cloud of CO2 gas from the lake
flowed out over nearby towns
and claimed 1,700 lives. The
victims were not poisoned, the
simply suffocated: being denser
than air, CO2 would tend to settle
near the ground and be rather
slow to disperse.