Physical Geography: Landforms

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• Physical Geography Landforms

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Relief on Land Topography
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• 7 major plates several minor plates
• Small plates / boundaries still unknown

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• Divergence, convergence, and shearing along these
  plate boundaries leads to orogenesis
  (mountain-building) and relief.

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Plate Tectonics Theory

• Plate boundaries main location for
  Earths volcanic and earthquake activity. This is
  main place where mountains are created.
• Type of plate boundary determines activity.
• 3 types
• divergent (spreading) compression force
• convergent (colliding) tension force
• transform (sliding past each other) shear force

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Plate Margins how do we know?

• Marked by volcanic and tectonic activity

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Sea Floor Spreading
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Divergent Plate Boundaries

• Landscape features
• land rift valleys, volcanic mountains, thinning
  crust
• ocean/sea rift valleys, undersea mountain ranges
  

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Convergent Plate Boundaries

• Activity
• subduction shallow to deep earthquakes
  volcanism (continental)
• Features
• ocean trench explosive volcanic mountains on
  continental margin

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Subduction Denser crust sinks beneath nearby
plate and is destroyed.
Explosive Volcano
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The Rock Cycle
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Earth Materials

• Formation of Earth
• Three major rock types
• Igneous
• Sedimentary
• Metamorphic

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Igneous Rocks

• Igneous (ignus fire)
• Formed from the cooling of molten rock
  (magma/lava), a process called crystallization.
• Slow cooling ? larger crystals gt dense rock
• Rapid cooling ? small crystals gt lighter rock

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• Two classes of igneous rocks
• intrusive formed inside the Earth
• extrusive formed at Earths surface

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Igneous Extrusive Rocks

• Cools rapidly - exposed to surface
• No visible crystals
• Examples
• - rhyolite - andesite -basalt

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Igneous Extrusive Landscapes
Flood Basalt, Northern California
Volcan Arenal, Costa Rica

• Volcanic dike and neck Shiprock, NM

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Some unique volcanic rock types

• ? Pumice (vesicular)
• - sometimes so light it floats!

• Obsidian ?
• glassy, curved fracturing
• used for arrowheads by Native Americans

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Typical Igneous Intrusions
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Igneous Intrusive Rocks

• Cools slowly (thousands of years)
• Visible crystals
• Examples
• - granite, andesite

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Exposed Batholiths
Sierra Nevada, CA
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Sedimentary Rocks
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Where do Sedimentary Rocks Form?

• Marine environments
• Continental shelf
• Continental slope and rise (deep sea fans)
• Abyssal plain
• Beach and barrier islands

• Terrestrial environments (non-marine)
• Rivers and floodplains (fluvial environment)
• Lakes
• Deserts (aeolian environment)

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Sedimentary Rocks
Relative Abundance by Type
Cementing
Compaction
Formation
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Limestone (CaCO3)
Shale (fine grains)
Sandstone (larger grains)
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Metamorphic Rocks or Thats very Gneiss, but I
dont give a Schist!
Schist (narrow foliation)
Gneiss (broad foliation)
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Metamorphic Rocks
Pemaquid Point, Maine
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Distribution of Rock Types
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What type?
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Metamorphic Banded Gneiss, Greenland, 3-3.8
billion years old
What type?
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What type?
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Sedimentary Sandstone in Bryce Canyon N.P.,
Utah
What type?
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Which type?
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Which type?
Extrusive Igneous Sunset Crater N.M., Arizona
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What type?
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Which type?
Folded Sedimentary - Sheep Fold, Wyoming
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Which type?
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Which type? Granite Joshua Tree N.P.,
California
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What type?
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What type?
Sedimentary - Vasquez Rocks, Southern California
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Distribution of Rock Types
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The Rock Cycle