PHYSICAL WORLD ESCI 243  -  NICHOLS COLLEGE ONLINE COURSE

Professor Mauri S. Pelto, 508-213-2168 peltoms@nichols.edu   

Volcanic Hazards

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Without volcanoes the world would have less land area and fewer islands.  Almost all our oceanic islands in the temperate to tropical regions of the world that are not near shore were created by volcanoes.  Volcanoes form in three tectonic settings subduction zones, hot spots and mid ocean ridges. 

Reading 96-122

Concept Questions:

1.  What is the difference between a pyroclastic flow and a lahar?  How far does each travel, what area is affected around the volcano?

2.  What regions of the United States have volcanoes and what is the tectonic setting of each region?

3.  How does  the US Geological Survey predict the eruption of volcanoes?

4. Why since ocean crust is destroyed at subduction zones are the oceans not shrinking?

Assignment: 

Essay: Identify one currently erupting volcano and identify its tectonic setting and its likely future behavior.  Identify the hazards it poses..  Secondly review the recent earthquake activity at Mt Rainier is there any pattern suggesting a buildup in activity, note the current time-depth plot for the last year of seismic activity at this link?  Below is the difference in seismic depth data from an actively erupting volcano at left and a non-erupting volcano at right.  Note the extensive activity at depth reaching the magma chamber under Mt. St. Helens when it was active.activity?

 

There are three primary types of volcanoes in terms of the hazards posed.  

 1.  Cinder Cone- Found in each of the three plate tectonic settings.  These volcanoes are small, but can form quickly from rapid ash fall.

2. Shield- Found only in hot spot regions these volcanoes produce lava and more lava.  The result is generally extensive lava plains or gentle large volcanoes such as in Hawaii.

3.  Strato or Composite- The are the large steep sided Mt Fugi, Etna, St Helens type volcanoes.  They pose hazards of ash fall, lava, pyroclastic flows, poison gas releases, lahars, explosive force and climate alteration.