UNIT 3: VOLCANOES Flashcards
Parts of a Volcano (5) [ Top -> Bottom ]
- Pyroclastic / Tephra
- Vent
- Crater
- Conduit
- Magma Chamber
upward movement of molten rock to low pressure environment
decompression melting
formed in
1. hotspots
2. mid-ocean ridges
decompression melting
formed in
1. subduction zones
2. island arcs
flux melting
when H2O / CO2 is added to rock
flux melting
when a plate sinks underneath another
subduction zone
when equilibrium of lithostatic & magmastatic pressure is interrupted due to change of the latter
eruption
expresses size of volcanic eruptions
Volcanic Explosive Index (VEI)
VEI is based on (3)
- Volume of erupted ash
- Duration of eruption
- Type of explosion
Factors of Viscosity (3)
- Temperature
- Composition
- Dissolved Gases
ejected molten rock from volcano
lava
Magma Compositions (3)
- Basaltic
- Andesitic
- Rhyolitic
[COMPOSITION]
1. Silica Content - Least
Basaltic
[COMPOSITION]
1. Viscosity - Low
2. Explosivity - Least
Basaltic
[COMPOSITION]
Shield and Cinder Cones
Basaltic
[COMPOSITION]
1. Silica Content - Most
Rhyolitic
[COMPOSITION]
1. Viscosity - High
2. Explosivity - Greatest
Rhyolitic
[COMPOSITION]
Lava Domes
Rhyolitic
volcano deaths are caused mostly by
the explosive shower of the molten rocks
active ingredients needed for the volcanoes to erupt
dissolved gases / volatiles
volatiles depend on the _____ of the magma
composition
[GAS]
1. Smell – lighting a match
2. Colorless
SO2 / Sulfur Dioxide
[GAS]
1. Smell - Rotten Egg
2. Colorless
H2S / Hydrogen Sulfide
[GAS]
1. Pale yellow
Fluorine / F2
bone degeneration / mottling of teeth
fluorosis
[GAS]
1. Colorless OR Fuming Liquid
Hydrochloric Acid / HCl
reaction of SO2 to water
acid rain
ejected materials such as volcanic rocks / gases / fragments
pyroclastic materials / tephra
pyroclastic materials a.k.a
tephra
Types of Tephra (3)
- Pumice
- Scoria
- Pele
[TEPHRA]
ORIGIN: Plinian
COMP: Gas rich high silica content
TEXTURE: Lots of voids
Pumice
[TEPHRA]
ORIGIN: Strombolian
COMP: Andesite & Basaltic
TEXTURE: Vesicular
Scoria
[TEPHRA]
ORIGIN: Eruption of basaltic lava
COMP: Basaltic lava
TEXTURE: Tear drop / hair like
Pele
mixture of different types of tephra moving down the slides of volcanic crater at high speeds
tephra flows
falling of fine materials / ballistic projectiles from the sky
tephra falls
Types of Tephra Flow (3)
- Merapi
- Pelean
- Soufriere
[TEPHRA FLOW]
gravitational collapse of a lava dome
Merapi
[TEPHRA FLOW]
release of nuee ardente
Merapi
[TEPHRA FLOW]
turbulent fast movement of hot gas
nuee ardente
[TEPHRA FLOW]
formation of block-and-ash deposit
Merapi
[TEPHRA FLOW]
dome that blocks the conduit is exploded under pressure
Pelean
[TEPHRA FLOW]
collapse of eruption due to loss of pressure
Soufriere
[TEPHRA FLOW]
results in a pumice flow
Soufriere
Effects of Tephra Flow (4)
- Burns
- Impact and Burial
- Inhalation of hot ash and gases
- Lahars and flooding
size classification of tephra that’s a little bigger than ash
lapilli
Types of Projectiles
- Volcanic Bombs
- Volcanic Blocks
- Lapilli
[TYPE OF PROJECTILE]
from fresh magma
Volcanic Bombs
[TYPE OF PROJECTILE]
from walls of the vent / crater
Volcanic Blocks
wet cement-like mixture of volcanic material
lahar
lahars mostly occur in _____ volcanoes
composite
Lahar Sources (3)
- Rainfall
- Crater lakes
- Snow-covered tops