Read this on-line USGS publication at the URL

http://pubs.usgs.gov/gip/volc

http://www.volcano.si.edu/gvp/volcano/index.htm#regions

Volcanoes of the World

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, orwhen 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 Hawaii-Emperor chain, Iceland, Azores, Yellowstone etc., andas 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 geo-magnetic 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 best-known and most-studied example of a divergent-plate boundary.

Lava fountains (5 p;10 m high)

spouting from eruptive fissures

during the October 1980 eruption of Krafla Volcano.

View of the first high-temperature vent (380 °C)

ever seen by scientists during a dive of the deep-sea 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)

either by the convergence of oceanic edges of plates

Volcanism occurs at the subducted margins that form ...

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 North-

east 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.

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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, tryhttp://www.ig.utexas.edu/research/projects/lips/lips.htmlAlso visit the USGS volcanoe sites, starting withhttp://volcanoes.usgs.gov/ and the links provided there.

Photograph by Lazlo Keszthelyihttp://volcano.und.nodak.edu/vwdocs/Parks/hawaii/recent_events/dinosaurs.jpg

Deccan traps, the ~106 km3 flood basalt province in peninsular

India,extruded at or about the K/T

boundary.

Mt. Pinatubo: June 13, 1991 El Chichon, March 1982

http://www.etl.noaa.gov/review/aq/post/e.html

Satellites tracked the spread of airborne sulfuric acid mist formed by SO2 from the 1991 eruption of Mt. Pinatubo, Phillippines

7/4-7/10/91 (after circulating the earth)

5/20-6/6/91 (before eruption)

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

El Chicon

Mt. Pinatubo

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-hour- long 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

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.

Lake Nyos, Cameroon