GEOG 1290 Lecture Notes - Lecture 14: Nazca Plate, Pacific Plate, Seismometer
4 Nov 2017
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Document Summary
Slide 5 volcanism extrusion of magma builds initial landforms. Magma = molten rock inside the earth. Lava = molten rock on the surface. Volcano forms at the end of a constricted vent in the earth"s surface where emitted lava and its contained gases form a conical or dome-shaped initial landform. May be described as explosive and non- explosive. Volcanic eruptions also lead to lava flows, rock fragments, ash and gases. And other regions (e. g. , islands of hawaii are on a hot spot ) Active volcanoes - have erupted in recent history. Dormant volcanoes - have not erupted, but show some evidence of recent activity. Extinct volcanoes - show evidence of long-term weathering and erosion. Viscosity (t nh d o) of magma and lava depends on its composition. Determined by the location of the volcano. Basaltic (mafic) low in silica, high in iron and magnesium. Acidic (felsic) - less magnesium and iron but more silica.
