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COURSE LECTURE NOTES:
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SCIENCE | MATTER |
SOLAR SYSTEM |
PLANETS | ATMOSPHERE |
WIND and TEMPERATURE |
HUMIDITY | WEATHERING |
SOIL |
SEASONS | MASS WASTING |
SEASONS and CLIMATE |
WIND WORK |
STREAMS | LAND FORMS |
GROUND WATER |
CAVES/KARST | THE OCEAN |
TIDES & ESTUARIES |
WAVES | GLACIERS |
GLACIAL LANDFORMS |
VOLCANOES | VOLCANOES |
CHON | PLATE TECHTONICS |
EARTHQUAKES |
ROCKS |
CLIMATE CHANGE |
VOLCANOES
Definitions
volcano - collection of igneous material around a vent
vent - hole that emits igneous material
igneous material - Rx & glass formed from melt
magma - melted rock with gas and maybe some crystals, starts 40 - 100 km below surface, loses gas when it reaches surface and becomes lava.
The three things that are emitted by a volcano
1. lava - liquid flow of magma near the surface that has lost
the gas content
2. gas - there are several different kinds
a. H2O (steam) - majority of gas, up to 99% in
Hawaiian volcanoes
b. CO2 - large quanities are dangerous, they will sink
and become deadly to humans and other animals. First sign is dizziness
c. sulfer combinations
d. Ar - inert gas - no effect
e. Fl - can cause illness and death, but is rare, mostly in South
Amecan volcanoes
3. pyroclastic material -
a. ash - fragments less than 2 millimeters in diameter of
lava or rock blasted into the air by volcanic explosions
b. lappili (used to be cinder) - fragments of lava or rock between 2 and 64 millimeters
in size that are blasted into the air by volcanic explosions.
c. bombs - Fragments of fluid or partially fluid lava or rock larger
than 64 millimeters in size that are blasted into the air by
volcanic explosions in a semi-solid, or partial molten, condition,
shaped in air. Also known as "cow pies" and various other names. Example -
d. blocks Fragments of lava or rock larger than 64 millimeters in size
that are blasted into the air by volcanic explosions. Blocks are ejected
during the eruption in a solid state. Example - Mt. St. Helens, Penatubo.
Magma (melted rock) - types (all are part of continuum)
| Type |
SiO2 |
Fe |
Color |
Viscosity |
Flow |
Explosiveness |
Lava Type |
Melt |
Temp |
Example |
| basalt |
50% |
15% |
dark (black) |
low |
1/2 - 3 mph |
low |
basalt |
high 20% |
900o C |
Mauna Loa |
| andesite |
60% |
8% |
grey |
medium |
medium |
medium |
mixed |
medium 15% |
1000oC |
Mt St. Helen |
| rhyolite |
70% |
2% |
light
white & others |
high |
slow |
high |
pyroclastic |
low 10% |
900oC |
Krakatau |
Types of volcanoes
1. Shield - basalt, very hot lava flow, gentle eruption with fire fountains. Slope usually < 10o
Examples:
a. Mauna Loa
b. Mauna Kea, 9 km from ocean floor, earth's higest.
c. Medicine Lake
d. Deception Island
e. Vulcan Cumbres
f. Skjalbreidur
g. Kilauea
h. Olympus Mons on Mars, 29 km high.
2. Complex (aka stratovolcano, composire cone)- layers of basalt and pyroclastic materials
Examples:
a. Mt. St. Helens
b. Shasta
c. Crater Lake
d. Fuji San
e. Visuvius
f. Vulcano
g. Mt. St. Hellens
h. Mt rainier
i. Parinacota, Chili
j. Redoubt, Aleutians
k. El Misti, Peru
l. Santorini - 1620 BC eruption destroyed the Minoan civilization.
m. Etna
n. Kraatau
o. Pelee
p. Pinatubo
3. Resurgent caldera - leaves a huge hole
a. 70% rhyolite, rhyolite rarely reaches the surface
b. extremely viscous
c. very violent
d. wide spread ash fall 10 - 30 km
e. changes that occur after magma sits
1) loses gas
2) begins to grow crystal
3) becomes more viscous
f. Examples:
1)Yellowstone
2) Long Valley, California
3) Valles Caldera- Bandelier Tuff
4) Toba, Sumatra
5) Cerro Galan, Argentina
Additional types of volcanoes (old lava)
A. Pyroclastic cone (aka cinder cone) - a steep (up to 40o, conical hill of pyroclastic materials (any type of lava) that accumulate around and downwind from a vent (shape may be distorted by wind). Most common volcano
Examples:
1. Pisgah
2. Amboy
3. Dish hill
4. Cold Creek Butte
5. Sunset Crater
6. Paracutin
7. Red Lake
8. La Poruna
B. maar - hole in the ground. Old lava forced out by new lava. Phreatomagmatic eruption
Examples:
1. Inyo Crater
2. Ubehebe - Death Valley
3. Salt Crater
C. Dome - a mound, has to be andesite or rhyolite (on Earth)
Examples:
1. Lassen Peak
2. Mammoth Mountain
3. Showa Sui San
4. Obsidian Dome
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