Download Lecture 6: Volcanoes I. Introduction II. Magma A. Magma vs Lava 1

Lecture 6: Volcanoes
I. Introduction
II. Magma
A. Magma vs Lava
1. magma
2. lava
B. Characteristics of lava
C. Factors that determine characteristics of lava and volcanic eruptions
1. composition of magma
2. temperature
3. amount of dissolved gases, primarily water
4. amount of silica
D. Silica content and viscosity
1. Definition of viscosity
2. Silica tetrahedra link to form polymers
3. Polymer formation causes increase in viscosity
E. Magma types and silica content
1. Granitic magmas:
2. Basaltic magmas:
3. Andesitic magma
F. Water content and granitic magmas
rocks or plate material may carry water when they are subducted or melted
1. water lowers the melting point
2.. dry granite
3. wet granite
G. Water and Basaltic magmas
III. Eruptive style
A. Violent Explosive Magmas
B. Non-violent magmas
IV Types of Volcanoes
A Shield Volcanoes
B.. Stratovolcano (Composite cones)
V. Volcanic Environments (where volcanoes form)
form at plate boundaries or are associated with hot spots
A. Ocean-ocean convergence
B. Ocean-continent convergence
C. Divergent margins
D. Hot spots
ex: Hawaiin islands
VI. Assessing Volcanic Hazards
A. Location
B. History
C. Pre-eruption activity