Volcanoes Flashcards
Dome or crypto dome
Often form in the vent within collapsed crater of stratovolcanoes
Occurs when Felsic lava piles up near vents because it is too viscous to flow easily.
Pyroclastic flow
Avalanche of hot ash and pumice and rock fragments
Very fast
Temp up to 500C
Lava flows
Consist of magma flowing along the earths surface
Generally slower
Lahars
A volcanic mudflow that consist of water, ash and rock fragments that forms from rapidly melting snow or glaciers.
Can reach up to 80km/hour
Two different kinds of lava
Aa lava
Pahoehoe lava
Aa lava
Is highly viscous and has a crumbly blocky appearance of basalt lava flow.
Pahoehoe lava
A smooth low viscous lava flow that forms into ropes stands
Basalt lava
Fine crystalline and cools very quickly
Andesite lava
Intermediate composition
Typically of subduction zones
Rhyolite lava
Mostly viscous flow - high silica content
Flows only reach 1-2 km from vent
Domes form above vent
Effusive lava eruption
Eruptions are small, localized and predictable,
Common of basaltic lava
Mainly in shield volcanoes
Three types volcanoes
Shield- Hawaii
Cinder cones- typically smaller
Strato-composite- mount fugi and saint helens
Shield volcanoes
Large volcanoes with very gentle slopes, dominated by basalt
Created by low viscosity lava flows
Minor pyroclastic eruptions at the crater or cinder cones along the flanks
Pillow lava
Basalt lava that falls into the ocean and forms pillow like shapes
Cinder cones
Eruptions of basalt composition, spattering
Steep slopes
