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Volcanic Structures
Figure 1 Types of Volcanoes
CINDER CONES- are produced by the eruption of viscous magma and are composed almost
entirely of pyroclastic deposits. These angular fragments form steep (30-40o)
and usually small
(< 1000') cones.
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Figure 3 Mayon volcano
MAAR - Also called "tuff cones," maarsare shallow, flat-floored craters that scientists interpret
have formed above diatremes as a result of a violent expansion of magmatic gas or steam; deep
erosion of a maar presumably would expose a diatreme.
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Figure 4Zuni Salt Lake Maar, New Mexico
VOLCANIC PLUGS- believed to overlie a body of magma which could be either still largely liquidor completely solid depending on the state of activity of the volcano. Plugs are known, or
postulated, to be commonly funnel shaped and to taper downward into bodies increasingly
elliptical in plan or elongated to dike-like forms.
Figure 5 Ship rock, New Mexico
LAVA DOMES- are formed by relatively small, bulbous masses of lava too viscous to flow any
great distance; consequently, on extrusion, the lava piles over and around its vent. A dome
grows largely by expansion from within. As it grows its outer surface cools and hardens, then
shatters, spilling loose fragments down its sides.
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Figure 6 Novarupta dome, Alaska
SHIELD VOLCANOES- are built almost entirely of fluid lava flows. Flow after flow pours out in
all directions from a central summit vent, or group of vents, building a broad, gently sloping
cone of flat, domical shape, with a profile much like that of a warrior's shield.
Figure 7 Mauna Loa, Hawaii
GEYSERS, FUMAROLES (SULFATARAS), HOT SPRINGS- springs are generally found in regions of
young volcanic activity. Surface water percolates downward through the rocks below the
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Earth's surface to high-temperature regions surrounding a magma reservoir, either active or
recently solidified but still hot.
Figure 8 Old Faithful Geyser, Wyoming
FISSURE VOLCANO -This type of volcano has no central crater at all, which makes it difficult to
recognize either from the ground or from space. Instead, giant cracks open in the ground and
expel vast quantities of lava that spread far and wide to form huge pools that can cover almost
everything around.
Figure 9 The 2010 fissure eruption at Eyjafjallajokull
FLOOD BASALT PROVINCES- This is another strange type of "volcano". Some parts of the world
are covered by thousands of square kilometers of thick basalt lava flows--some flows are more
than 50 meters thick, and individual flows extend for hundreds of kilometers.
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LAVA MOUNDS- Some basaltic volcanoes have no sign of a crater, but are gently sloping
mounds
Figure 12 Mount Cottrell, Victoria
CUMULO-DOMES- When viscous lava is extruded, it sags and spreads into convex dome-like
bodies called cumulo-domes. These may be almost independent, or may be associated with andpartly intrusive into previously deposited pyroclasts.
Figure 13 Lassen Peak
MONOGENETIC FIELDS- don't look like "volcanoes", rather they are collections of sometimes
hundreds to thousands of separate vents and flows. Monogenetic fields are the result of very
low supply rates of magma.
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Figure 14 San Fransisco volcanic field
SOURCES:
http://pubs.usgs.gov/gip/volc/types.html
http://www.geocities.ws/alhy731/volcanoes/type.html
http://geography.unt.edu/~williams/geog_3350/examreviews/volcanic_structures.htm
http://geoenviron.wordpress.com/2012/02/24/structure-of-volcanoes/
http://pubs.usgs.gov/gip/volc/types.htmlhttp://pubs.usgs.gov/gip/volc/types.htmlhttp://www.geocities.ws/alhy731/volcanoes/type.htmlhttp://www.geocities.ws/alhy731/volcanoes/type.htmlhttp://geography.unt.edu/~williams/geog_3350/examreviews/volcanic_structures.htmhttp://geography.unt.edu/~williams/geog_3350/examreviews/volcanic_structures.htmhttp://geography.unt.edu/~williams/geog_3350/examreviews/volcanic_structures.htmhttp://www.geocities.ws/alhy731/volcanoes/type.htmlhttp://pubs.usgs.gov/gip/volc/types.html