Chap. 9 Tectonics, Earthquakes, and Volcanoes

Chap. 9 Tectonics, Earthquakes, and Volcanoes

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Mount Everest.

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Mount Everest from the Space Shuttle; loc mapEG6_Figure_09_01a-L

Bam, Iran >30k dead 2003 6.9M

EG6_Figure_09_01b-LTrans AK pipeline knocked off supports 7.9 M Denali eq in2003 http://pubs.usgs.gov/fs/2003/fs014-03/ >700 died or 4x?

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2005 Muzaffarabad Pakistan-Kashmir M 7.6 70k died

EG6 Fi 09 01d LM 7.9 eq in Chengdu China 2008; 83k died.

EG6_Figure_09_02-LHypsographic curve - distrib of land by area and elev

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Topographic regions

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Continental shields--cratons exposed at Earth’s surface.

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Shield showing glacial striations

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Crustal formation: sea floor spreading forms new ocean crust. Subduction of oceanic lithosphere creates volcanic arcs atop the subduction zone. Ex. Cascadia!

Accreted terranes--the great tectonic breakthrough of 1980s. Ex is Wrangell mtns

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EG6 Fi 09 07 LFault types

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Crustal deformation - folding and faulting

Anticlines - convex upward

Synclines - concave upward

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Syncline, Maryland

EG6 Figure 09 08c-LRoadcut near the San Andreas Fault

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Folding in the Zagros crush zone Iran

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Black Hills of ND shaded relief—makes it easier to tell it’s a dome.

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Normal fault (tension) and Wasatch Front in Utah

Tapestry of Time and Terrain

Tapestry—The Great Basin

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Reverse or thrust fault (compression); ex from BCEG6_Figure_09_11c-L

Strike slip (shearing) ex: San Andreas

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Four quakes in southern CA

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Horst and grabenlandscape

The Alps

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Ocean-continent

subduction

Ocean-ocean with subduction

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Collision of two continental tectonic plates

Collision of two continental tectonic plates

Ocean-continent plate collision w/

subduction

Ocean-ocean plate collision with subduction

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The Appalachians

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Tectonic settings of volcanic activity

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Mount Hood, a composite volcano in the Cascade Range is composed largely of dacite and andesite

Basalt of the Miocene Columbia River Basalt Group in the Columbia River Gorge

Effusive basalt is low silica and thus low viscosity, so it flows more easily than more sticky lavas

EG6_Figure_09_29-LKilauea shield volcano

EG6_Figure_09_30-LWhite Island off New Zealand, a composite volcano

Mount St. Helens prior to the 1980 eruption, and Spirit Lake.

An eruption that changed volcanology, and us!

Mount St. Helens, 1980

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Debris avalanche deposit and North Fork Toutle River after the eruption. View to the east; Mount St. Helens in the distance.

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The Mount St. Helens eruptive sequence 5/18/1980, shown with photos (from Keith Ronnholm) and diagrams.

EG6_Figure_09_31-LA dacite (higher silica) volcanic bomb from Mount St. Helens (left) compared to basalt (lower silica) lava from Kilauea. More sticky dacite is explosive; basalt is effusive (flows more readily).

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Lava flowing into the ocean from Kilauea volcano.

Pu’u O’o vent on the east flank of Kilauea has changed many times since formed.

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Mount Rainier (composite volcano) compared with Mauna Loa (shield volcano). Mauna Loa is Earth’s largest volcano.

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Diagrammatic view of a typical composite or “stratovolcano”. This type of volcano is commonly associated with subduction zones.

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Long Valley is a “restless caldera” in California. Several ski patrol members died there a few years ago when they fell into a pit filled with carbon dioxide gas from the volcano. Calderas are much more challenging to monitor than smaller volcanic systems such as composite volcanoes

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