Coastal & Marine Geology InfoBank

Home FACS Activities Atlas Geology School Related Sites More

USGS CMG InfoBank: Volcanoes and Magma

Skip navigational links
Loading
Dictionaries: Our Mapping Systems   The USGS and Science Education   USGS Fact Sheets   Topics   Keywords   Data Dictionary   Metadata Dictionary   Computer Terminology   Digital Formats  
InfoBank Terms: Activity ID   activity overview   crew   digital data   formal metadata   lines   metadata   NGDC   port stops   project/theme   region   ship   stations   time   virtual globe   year  
Data Types: bathymetry   biological   geochemical   gravity   ground penetrating radar   imaging   LIDAR   logs   magnetics   metering equipment   navigation   samples   seismic   total station   definitions disclaimer  
Data Formats: ARC coverage   E00   FGDC metadata   gridded/image   imaging   material   scattered/swath   Shapefile   vector/polygon  
Comment: 02:19 - 03:46 (01:27)
Source: Annenberg/CPB Resources - Earth Revealed - 13. Volcanism
Keywords: "James Sadd", volcano, magma, "interior of the Earth", eruption, "volcanic gas", "volcanic ash", atmosphere, climate, Sun, "sea floor", "mid-oceanic ridge", crust

Our transcription: Volcanoes are proof that the interior of the Earth is very hot, hot enough, in fact, to melt rock.
This molten rock called "magma" is less dense than the surrounding unmelted rock. It rises bouyantly, just as currents of hot air rise from the surface of the Earth.
Where the magma reaches the Earth's surface, volcanoes erupt. Different types of volcanoes can erupt in very different ways.
In some eruptions magma pours out onto the surface of the Earth in rivers of molten rock called "lava flows".
In others, high gas pressures underground cause the volcano to erupt explosively.
The magma is sprayed into the air as a cloud of very small hot particles called "volcanic ash".
This fine rock powder can remain aloft in the atmosphere for days and travel thousands of kilometers before finally settling to the surface of the Earth.
Sometimes volcanic ash can remain suspended in the atmosphere for months, blocking out sunlight and affecting global weather.
Volcanoes not only erupt in different ways, but they're also found in a wide variety of geologic environments.
There are about 500 known active volcanoes on dry land, but most volcanic activity occurs in places hidden from view.
There are probably several thousand active volcanoes on the floor of the open ocean, and most of these lie astride mid-ocean ridges, where Earth is forming new crust.

Geology School Keywords
Skip footer navigational links

Coastal and Marine Science Centers:  Pacific   St. Petersburg   Woods Hole  
InfoBank   Coastal and Marine Geology Program   Geologic Information   Ask-A-Geologist   USGS Disclaimer  


Accessibility FOIA Privacy Policies and Notices

Take Pride in America logo USA.gov logo U.S. Department of the Interior | U.S. Geological Survey
URL: http://walrus.wr.usgs.gov/infobank/programs/html/school/moviepage/12.01.03.html
Page Contact Information: InfoBank staff
Page Last Modified: Thu Oct 31 04:26:33 PDT 2013  (chd)