Landforms of California

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• Landforms of California

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Overview

• Geologic Time
• Movements of the Continents
• Earth Materials
• Tectonic Forces
• Weathering and Erosion Processes
• Erosional Agents and Deposition

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Geologic Time

• Pretend the age of the earth (4.6 billion years)
  is compressed into one calendar year.
• January 1 - Earth and planets formed
• Early March - liquid water stands in pools.
• Late March - earliest life
• July - oxygen is important part of atmosphere
• October 25 - multicellular organisms
• Late November - plants and animals abundant
• December 15 to 25 - dinosaurs arise and disappear
• 1120 pm, December 31 - Humans appear
• One second before midnight - Automobile invented

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The Earths Interior

• General trends temperature, density
• Horizon composition, behavior

Distance 6730 km (3963 miles)
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Earth Materials

• 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 Intrusive Rocks

• Cools slowly (thousands of years)
• Visible crystals
• Examples
• - granite - diorite - gabbro

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Igneous Extrusive Rocks

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

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Typical Igneous Intrusions
Know Batholith and Dike
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Exposed Batholiths
Sierra Nevada, CA
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Sedimentary Rocks
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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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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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Metamorphic Rocks or Thats very Gneiss, but I
dont give a Schist!
Schist (narrow foliation)
Gneiss (broad foliation)
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The Unstable Landscape
California Plate Tectonics
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• Crustal Processes
• Destruction (subduction)
• Creation (volcanism )
• Alteration / deformation (folding and faulting)

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Introduction

• Plate boundaries main location for
  Earths volcanic and earthquake activity.
• Type of plate boundary determines activity.
• 3 types
• diverging (spreading)
• converging (colliding)
• transform (sliding past each other)

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Convergent Plate Boundaries

• Action
• collision destructional or constructional
• Activity
• depends on type of convergence
• 3 types ocean-continent, ocean-ocean, cont.-cont.

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Convergent Ocean-continent

• Action
• collision destructional (subduction of ocean
  plate)
• Activity
• shallow to deep earthquakes volcanism
  (continental)
• Features
• ocean trench volcanic mtns on continental margin

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Volcanoes Explosive

• Composite cones (stratovolcano)
• pointed, steep-sided, tall volcanoes
• Composite layers of pyroclastics and lava
  (mostly felsic)
• Explosive and dangerous found near subduction
  zones

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Volcanoes Explosive
Arenal, Costa Rica
Mt. Shasta, California
Mt. Lassen, California
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Crustal DeformationFolding, Faulting, and
Earthquakes
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Introduction

• Crustal Processes
• Destruction (subduction)
• Creation (volcanism - convergent/divergent)
• Alteration / deformation (folding and faulting)

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Crustal Deformation

• Outcome / result of battle
  Stress v. strain (force v. resistance)
• Stress force imposed on the rock
  (tension, compression and shear)
• Strain how the rock responds to the stress
  (folding / bending or faulting / breaking)
  Is the rock brittle or ductile?

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• Figure 12-7

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Faulting

• Definition fractures where some type of
  displacement (movement) has occurred along a
  break in rock.
• Three types
• normal
• reverse/thrust
• transform
  (strike-slip)

Carmel Valley Fault, CA
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Normal Faults

• Tensional stress
• Earthquake and displacement along fault plane ?
  fault scarp

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Landforms - Normal Faulting
Owens Valley, CA
Sierra Nevada, CA
Grand Tetons, WY
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Basin and Range

• Horst and graben (hill and grave)

Death Valley/ Panamint Ranges Why saline?
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Landforms Normal Faulting

• Grabens (Graves)

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Basin and Range
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Transform Plate Boundary

• Action
• shear (lateral motion)
  
• no loss/gain of plate material

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• San Andreas fault system
• How long is it? About 1000 km
• Relative motion of the Pacific
  Plate? _at_ 2 inches (5 cm) northwest
  per year. In 10 million years Los Angeles will be
  off of San Francisco .

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San Andreas Fault System - Southern California
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Transform Plate Boundary

• Activity
• shallow to moderate earthquakes
• little to no volcanism
• http//quake.usgs.gov/
  recenteqs/

Tremblor Range
Dragons Back
Carrizo Plain, CA (view to the east)
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Transform Plate Boundary

• Features
• shallow, linear rift valleys
• sag ponds

Carrizo Plain, central CA
San Andreas Lake (Crystal
Springs Reservoir) - looking south along
fault - San Francisco water supply -
geology ? vegetation
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Transform Plate Boundary

• Features
• offset streams, objects

Stream channel offset, Carrizo Plain,
central CA
1906 earthquake offset, Point Reyes,
CA
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The Geography of Earthquakes

• USA 1977-1997 earthquake events
• USA every state except ND, FL

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The Geography of Earthquakes

• Globally primarily at plate boundaries
• Intraplate earthquakes do occur!

Mag 6.5
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Earthquakes

• Earthquakes are the shaking or vibration of the
  ground as a result of rocks suddenly breaking
  along a fault.
• Focus (hypocenter) rupture point
• Epicenter point on surface above focus
• Foreshocks
• Aftershocks

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Process the earthquake cycle (elastic rebound
theory)

• Earthquakes are a release of energy in the
  form of a seismic wave (vibrates the crust).
• Plate movement ? strain builds rocks locked
  together (frictional bond)
• Rocks bend ? hit limit --gt rupture/break
• Cycle repeats ?start-stop motion along fault

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Seismic waves

• Some of the waves that are generated by an
  earthquake travel within the earth and other
  travel along the surface, creating surface waves.
• Waves traveling within the earth are known as
  body waves.

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Surface Waves

• Surface waves cause the most damage to buildings
  during an earthquake.
• Surface waves can set up liquefaction in wet
  alluvium. This is where the most extensive damage
  to buildings occurs.
• Liquefaction wavelike, almost liquid, rolling of
  surface
• Alluvium fine material deposited by water over
  many years.

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Measuring Earthquakes

• seismograph records the vibrations
  of the crust
• Richter Scale measuresvibration, not damage.
• seismogram tracing record

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Major California Earthquakes

• Fort Tejon, 1857 - 8.0 magnitude
• San Francisco, 1906 - 7.9 magnitude
• 1933 Long Beach - 6.3 magnitudeDestroyed
  Glendale College Buildings!
• San Fernando, 1971 - 6.6
• Northridge, 1994 - 6.7
• Hector Mine, 1999 - 7.1

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Fort Tejon, 1857

• TIME January 9, 1857
• LOCATION 35 43' N, 120 19' W
• about 72 km (45 miles) northeast of San Luis
  Obispoabout 120 km (75 miles) northwest of
  Bakersfield,as shown on the map (epicenter
  location uncertain).
• MAGNITUDE Mw 8.3 (approx.)
• TYPE OF FAULTING right-lateral strike-slip
• FAULT RUPTURED San Andreas fault
• LENGTH OF SURFACE RUPTURE about 360 km (225
  miles)
• MAXIMUM SURFACE OFFSET about 9 meters (30 feet)

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San Francisco Aftermath, 1906 Magnitude 7.9
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San Francisco, 1906 Magnitude 7.9
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