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Class AnnouncementsClass AnnouncementsTerm Break extra credit option due by end of period today.
Sign up to attend a Papago Park extra credit field trip (worth 20 points).
Options:
Wed., April 16: 10-11AM or 4-5 PM
Thurs., April 17: 10-11AM or 2-3 PM
Today’s Lecture:Today’s Lecture: Chap. 9 Chap. 9 VolcanoesVolcanoes
Class presentations:
Cancer-causing gas in Beverly Hills CA - Michael Zara
Mt. Rainier - Nathan Policar
Intermediate volcanoes (cont.)
Calderas
Volcanic hazards
Case Study: Mt. Saint Helens
Economic aspects:
Hydrothermal activity
Mineral deposits
Volcanic Activity on Other Planets
a.a. Calderas Calderas
b.b. Lava domes Lava domes
summit crater greater than 1 km wide from collapse of summit
viscous felsic magma usually form after explosive eruption of gas-rich magma
Some Other Important Volcanic Features
Fig. 09.11ab
W. W. Norton
Volcano startsto erupt.
Full magmachamber
Main explosiveeruption
Magma chamberempties.
Newly formedcaldera
Collapsed blocks
Empty magmachamber
New volcaniccone grows.
Lake fillscaldera.
Ash and debris
Fig. 09.29b
© 1997 Birke Schreiber
Mount St. Helen’s
Lava dome
Case study: Mt. St. Helens
Case study:Mt. St. Helens
•Located in the Cascade volcanic range, NW US.
•Result of past/present subduction of oceanic crust in the Cascadia Trench
•Many volcanoes there are still active
9500’
8150’(1350’ shorter!)
Case study:Mt. St. Helens
Ejected nearly a cubic kilometer of ash & rock debris
59 deaths
Ash blown over 11 miles high!
Fig. 09.15
W. W. Norton
Fig. 09.16abc
W. W. Norton
Fig. 09.22e
Photo by J. Marso, U.S. Geological Survey
Volcanic mudflows
Mount Saint Helens
A lava dome
formed
in crater
after major
eruption.
Hydrothermal Systems:
Develop anywhere that fluids coexist with a heat source.
Typical heat source a magma intrusion.
Effects: Alteration of adjacent rocks and deposition of mineral deposits, often of economic importance.
Also a source of geothermal energy.
GENERAL FEATURES OF HYDROTHERMAL
SYSTEMS
Hydrothermal Springs: Natural Laboratories for studying microbial fossilization.
Grand Prismatic Spring
1: Lava flows
2: Ash falls
3: Ash flows
4: Mud flows
Videos: Types of Volcanic Eruptions
VENUS
Volcanoes Elsewhere in Solar System
MARS
Fig. 09.30a
JPL / NASA
Olympus Mons: Largest Volcano in the Solar System
Olympus Mons, Mars
Jupiter’s moon “Io”
From Scientific American, Feb 2000
Jupiter’s moon “Io”
Fig. 09.30b
JPL / NASA
Volcanic Eruptions in Progress on Io