Volcanoes types and intrusive forms.
Types of Volcanoes(listed in order of increasing magma viscosity)
•Basaltic Plateau (Flood Basalt Plateau)
•Shield Volcano
•Cinder Cone
•Composite Volcano (Stratovolcano)
Basaltic Plateau (Flood Basalt Plateau)
• Eruption of very low viscosity basaltic lavas
from fissures to form large plateaus.
Shield Volcano
• Eruption of low viscosity basaltic lavas
• High with broad, gently sloping flanks
• Most form on ocean floor
• Examples: Hawaii (Muana Loa, Kilauea),
Iceland, Galapagos Islands
Cinder Cone
•Eruption of mostly loose, cinder-sized pyroclastic material from gas-rich basaltic magma
•Sometimes erupt lava flows
•Small: typically < 300 m elevation
Composite Volcano (Stratovolcano)
•Alternating layers of lava flow and pyroclastic material. Lava flows protect underlying pyroclastic deposits from erosion.
•Characterized by explosive eruptions
–Typically erupt greater volume of pyroclastic material than lava flow
•High with steep flanks
•Example: Mt. St. Helens, WA; Mt. Rainier, WA; Mt Hood, OR; Popocatepetl, Mexico; Pinatubo, PhilippinesMt. St.
Features Common to Stratovolcanoes
•Crater–steep walled depression at or near summit from which lava and pyroclastic materials are ejected
•Dome (Spine)–Accumulation of viscous lava directly over a volcano’s vent. Acts to ‘plug’ the underlying vent.
For volcanic types go to:
http://usuarios.geofisica.unam.mx/cecilia/cursos/IgRs&Mch4_Wicander-ChangE.pdf
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