volcanic and tectonic landforms
TRANSCRIPT
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Visualizing Physical Geography
Copyright 2008 John Wiley and Sons Publishers Inc.
Volcanic and Tectonic Landforms
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Visualizing Physical Geography
Copyright 2008 John Wiley and Sons Publishers Inc.
Continental landforms are the result of endogenic and exogenicprocesses.
Endogenicprocess: works from within the Earth
Produces initial landformsUplifts; brings fresh rock to the surface
Powered by Earths internal energy
Exogenicprocess: works at Earths surfaceWears down initial landforms
Creates sequential landforms
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Visualizing Physical Geography
Copyright 2008 John Wiley and Sons Publishers Inc.
Volcanic Landforms
Volcanic ActivityVolcano: conical, circular structure built by accumulation of lava flows andtephra (volcanic ash)
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Visualizing Physical Geography
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Volcanic Landforms
Volcanic Activity
Many volcanoes arelocated on subductionboundaries or riftzones.
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Visualizing Physical Geography
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Volcanic Landforms
Stratovolcanoes
The nature of an eruption depends on the type of magma involved.
Felsic lavas associated with stratovolcanoes Rhyolite, andesite
Thick, resistant to flow
Builds steep slopes around volcanic vents
Tall, steep cone, with crater
Stratovolcano: volcanoconstructed of multiple layers oflava and tephra (volcanic ash)
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Visualizing Physical Geography
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Volcanic Landforms
Stratovolcanoes Most active stratovolcanoes on
circum-Pacific mountain belt
Associated with subduction zones Felsic lavas produce explosive
eruptionsLarge amounts of gas under highpressure
Central part of volcano mayexplode, leaving caldera: centraldepression
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Visualizing Physical Geography
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Volcanic Landforms
Stratovolcanoes
Exogenic processes erodestratovolcanoes
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Visualizing Physical Geography
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Volcanic Landforms
Shield Volcanoes
Shield volcanoes are associated
with mafic lava (basalt) Lava thin, not viscous Holds little gas
Usually quiet eruptions
Lava travels long distances, spreadsout in thin layers
Shield volcanoes are roundeddomes, with gentle slopes
Shield Volcano: low, often large, dome-like
accumulation of basalt lava flows emergingfrom long , radial fissures on flanks
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Visualizing Physical Geography
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Volcanic Landforms
Shield Volcanoes
Some shield volcanoes
form overhotspots:stationary plumes ofbasaltic lava welling upfrom the mantle
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Visualizing Physical Geography
Copyright 2008 John Wiley and Sons Publishers Inc.
Volcanic Landforms
Shield Volcanoes
The Hawaiian chain was
formed by the movement ofthe Pacific Plate over ahotspot.
Chain of islands shows motionof the plate
Active volcanoes at thesouthern end
Guyots (sunken islands) at thenorthern end
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Visualizing Physical Geography
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Volcanic Landforms
Shield Volcanoes
Basaltic lava also erupts:
Along midocean ridgesSeafloor spreadingMany volcanic islands alongmid-Atlantic Ridge
Beneath continental platesHotspot generates largevolume of basaltic lava
Forms flood basalts
Continental flood basalts,Columbia Plateau, U.S.
Basaltic lava on Heimaey Island,Iceland, on mid-Atlantic Ridge
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Visualizing Physical Geography
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Volcanic Landforms
Geothermal Energy Sources
Geothermal energyis energy from the heat in the Earth
Regions near hot springs and geysers have hot water that can betapped and used to drive turbines to generate electricity.
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Visualizing Physical Geography
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Tectonic Landforms
Fold Belts
Compression fromtectonic activityproduces folds in rockstrata
Anticlines: upbendsSynclines: troughs
Folds: corrugations of
strata caused by crustalcompression
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Visualizing Physical Geography
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Tectonic Landforms
Fold BeltsFolds erode to form ridge-and-valley landscape
Ridges and valleys parallel
Folds may be plunging folds
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Visualizing Physical Geography
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Tectonic Landforms
Faults and Fault Landforms
Fault: sharp break in rock with aslippage of the crustal block on oneside with respect to the block on theother
Fault lines may extend for manykilometers
Most major faults extend downseveral kilometers
Fault slippage varies from 1 cm to 15 m
Four main types of faults:Normal
Transcurrent
Reverse
Overthrust
T t i L df
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Visualizing Physical Geography
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Tectonic Landforms
Faults and Fault Landforms
Normal faults are produced by crustal extension
T t i L df
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Visualizing Physical Geography
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Tectonic Landforms
Faults and Fault Landforms
The East African Rift Valley is a graben
T t i L df
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Visualizing Physical Geography
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Tectonic Landforms
Faults and Fault LandformsTranscurrentorStrike-slip Faults are producedwhen tectonic plates move past each other
horizontally
T t i L df
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Visualizing Physical Geography
Copyright 2008 John Wiley and Sons Publishers Inc.
Tectonic Landforms
Faults and Fault Landforms
Reverse and overthrustfaults are
produced by compression in thecrust
T t i L df
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Visualizing Physical Geography
Copyright 2008 John Wiley and Sons Publishers Inc.
Tectonic Landforms
Faults and Fault Landforms
Repeated faulting can produce high fault
scarps
Landforms are modified by erosion
E th k
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Visualizing Physical Geography
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Earthquakes
Earthquake: a trembling orshaking of the ground
produced by passingseismic waves
Most earthquakes produced bysudden slippage along faults
Energy builds up until the faultslips, releasing seismic waves
Earthquake magnitudes may bedescribed on the Richter Scale
E th k
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Visualizing Physical Geography
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Earthquakes
Earthquakes usually occur on plate boundariesLarge-magnitude earthquakes are generated along subduction zones
Transcurrent faults on transform boundaries cause moderate to strong
earthquakesSpreading plate boundaries produce moderate earthquakes
Some earthquakes occur in the centers of continents, away from plateboundaries
E th k
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Visualizing Physical Geography
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Earthquakes
Earthquakes Along the San Andreas FaultSan Francisco Earthquake, 1906
700 lives lost
$30 billion damage Generated by movement on San Andreas Fault This portion of the San Andreas has not moved since 1906
Earthquakes
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Visualizing Physical Geography
Copyright 2008 John Wiley and Sons Publishers Inc.
Earthquakes
Earthquakes Along the San Andreas Fault
Loma Prieta Quake, 1989
62 lives lost$6 billion damage
Occurred on fault near the San Andreas
Did not fully relieve strain on San Andreas
Southern California: likelihood of very large
earthquake within 30 years is 50%
Earthquakes
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Visualizing Physical Geography
Copyright 2008 John Wiley and Sons Publishers Inc.
Earthquakes
Seismic Sea WavesTsunami: train of sea waves triggered by an earthquake (or other seafloordisturbance) traveling over the ocean surface
Banda Aceh, Indonesia, beforeand after 2004 tsunami
Kalutara Beach, Sri Lanka,before and during 2004 tsunami
Landforms and Rock Structure
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Visualizing Physical Geography
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Landforms and Rock Structure
Exposed Batholiths and Monadnocks
Batholiths: huge bodies of intrusive igneous rock Form hilly or mountainous uplands
Monadnock: a mountain that rises out of asurrounding plain and that develops because itconsists of more resistant rock than the bedrock ofthe surrounding region