Rivers, volcanoes, earthquakes

• earthquake- the ground begins to shake due to the sudden movement of rock blocks

  • fault blocks become “locked”
  • stress becomes too great and rupture occurs
  • plate boundaries
• Elastic rebound theory

  • earth wants to return to its original state
  • stress causes rupture but earth get to snap back to its original shape
  • foreshocks & aftershocks
• earthquake can be generated by a multitude of things..

  • faults
  • volcanoes
  • ground collapses
  • human activity (bombs)
• Most common earthquakes are from movement of rock blocks/tectonic plates
• Compression - reverse fault
• Extension - normal fault
• Shear - strike slip fault
• Reverse thrust

  • compression
  • hanging wall goes up
  • associated with convergent boundary
  • deep to shallow earthquakes
  • most dangerous and most damage
• Normal faults

  • extension
  • hanging wall goes down
  • horst & graben
  • associated with divergent boundary or rift zones
  • shallow earthquakes
• Strike-slip faults

  • motion is horizontal (no hanging wall)
  • right (lateral) or left (lateral) steps
  • no vertical displacement
  • shallow earthquakes
  • can have large earthquakes
• hypocenter/focus

  • where slip began
  • where seismic waves originate from
• Epicenter

  • point directly above hypocenter
• Body waves (p&s waves)

  • travel entirely within the earth and propagate spherically from hypocenter
• P(primary) wave

  • smallest and fastest wave
  • push and pull motion
  • changes particle VOLUME
• s (secondary) wave

  • shear motion
  • cannot travel through liquids and gasses
  • change particle SHAPE
• Body waves change velocity and direction as they encounter different layers
• Surface waves

  • Rayleigh wave
  • love wave
• Seismometer

  • uses inertia (stationary objects remain stationary unless acted upon by an outside force)
  • needs to be placed in very quiet area
• P-S interval

  • time log between p and s waves determines earthquakes distance
  • greater the space the farther the earthquake
• Determining epicenter

  • 3 stations minimum
  • p-s wave interval distances
  • intersection of circles mark epicenter
• Richter scale

  • measures magnitude (strength of earthquake)
  • no longer used
• Moment magnitude

  • what we currently use
  • way to measure earthquakes
• landslides

  • sudden movement of the ground downslopes
• Earthquake hazards

  • ground shaking
  • landslides
  • sediment liquefaction
  • tsunami
• Sediment liquefaction

  • when a saturated or partially saturated soil substantially loses strength and stiffness from the ground shaking
• Tsunami

  • giant waves cause by seafloor VERTICAL
  • Most damaging and dangerous
• After effects of earthquakes

  • fire
  • disease
• hydrologic cycle

  • 1/4 of rainfall falls on land sculpting the earths landforms
  • evaporation -> condensation/precipitation -> runoff
• Rainwater follows topography
• Drainage basins

  • form tributaries
  • overtime will be eroded away by river
• Main river systems

  • Columbia
  • colorado
  • Mississippi
• Lighter sediment

  • chemical weathering
  • dissolved or suspended load
• Denser sediment

  • physical weather
  • bed load = bounces, slides, rolls
• River flow velocity controlled by

  • discharge
  • channel size, shape, roughness
  • gradient (slope)
• Discharge

  • amount of water varies seasonally
• anatomy of a river system

  • zone 1 - sediment production
  • zone 2 - sediment transportation
  • zone 3 - sediment deposition
• zone 1

  • sediment production
  • steepest part of river
  • steep gradient = fast speeds
  • erodes down
  • bedrock streams
• Base level

  • where the water body loses its downward erosional power
  • sea level, lake level, stream level
• zone 2

  • sediment transportation
  • main trunk
  • not as steep
  • valley widening
• zone 3

  • sediment deposition
  • river reaches the ocean or lake it slows down
  • flatter land
  • slower velocity
  • distributaries