Transcript Mountain Building, Earthquakes, and Sea Floor

Mountain
Building,
Earthquakes,
and Seafloor
Landforms
Mountain Building
 Terms:


Ranges  linear
association of peaks
System 
combination of
ranges
Mountain Building
 Mountains

form in various ways:
Volcanic
 Due
to both convergent and divergent plate
boundaries

Differential weathering and erosion
 Erosion

of batholiths that are revealed at the surface
Block faulting
 Tensional
stress pulls and causes
normal faults
 The uplifted blocks are horsts
 The down dropped blocks are
grabens
Mountain Building
 Orogeny
 mountain
building episodes


This occurs at
convergent plate
boundaries
You will see deformed
sediments present at a
current or historical
orogeny
Mountain Building
 Continent
– Continent Convergence
 This happened when the Indian and
Eurasian plates collided.
 Because of this convergence that
continues even today the Himalayans
are still “growing”
 There are other convergences that
produce orogenies but this is the main
one
Earthquakes
 Earthquakes
are
vibrations of the earth,
caused by a sudden
release of energy,
usually as a result of
faulting
 Magma
movement can
also trigger earthquakes
 Usually caused by a
transform plate boundary
Earthquakes
 Aftershocks
are adjustments along a fault
after an earthquake, but still are felt as
vibrations
 This is because of the elastic rebound
theory

When the strength of rocks is exceeded, the
rocks will snap back to their former shape
Earthquakes Terms:
 Seismology
 the study
of earthquakes
 Seismograph 
instrument which
measures earthquakes
 Focus  location where
the earthquake
originates
 Epicenter  location on
earth’s surface directly
above the focus
(usually what is
mentioned by the
media)
Earthquakes
 Seismic
Waves
 Body
Waves travel through the Earth
 P waves
 Primary
waves
 These are the fastest, and the first detected
 They act as compressional waves
Earthquakes
S
waves
 Secondary
waves
 These are shear waves/transform waves, they
move perpendicular to line of travel
 These waves cannot be transmitted through a
liquid
Earthquakes
 Surface
Waves are waves
that travel on the ground
 Rayleigh waves (R-waves)
 Slower
moving wave
 Moves similar to water waves
(circular)
 Love
waves (L-waves)
 Lateral
motion waves
 These waves cause damage
to the foundations of many
buildings
Earthquakes
 Locating
 You
the Earthquake
need three locations where P and S waves
were measured
 With those locations circles can be drawn that
have radii equal the distance measured from a
time-distance graph
Earthquakes
 The
intersection of these three circles is
the location of the epicenter
 This needs to be done quickly so the
population can be warned about other
effects of the earthquake
Earthquakes
 Effects:
 Ground
shaking (most
obvious)
 Ground failure
 Solifluction and
liquefaction
 Slumping
 Landslides
 Fire
 Tsunamis  seismic sea
waves
Earthquakes
 Distribution:
 80%
occur in the circum-Pacific belt, along
convergent plate margins
 15% occur in the Mediterranean-Asiatic belt
 15% are scattered, some occur in plate interiors
 1811-1812
New Madrid, MO
 Failed rift valley
Seafloor
 The
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Ocean Basins
97.2% of Earth’s water is in the Oceans
Pacific Ocean
Atlantic Ocean
Indian Ocean
Arctic Ocean
Seas are smaller bodies
of water
 Red Sea
 Dead Sea
 Caspian Sea
Seafloor
 Profile:



Coast
Continental margins
 Continental shelf
 Continental slope
 Continental rise
Deep ocean basin
Seafloor
 Continental

Margins
Types:
 Active

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Oceanic plate is subducted beneath continental plate
(convergent plate boundary)
No continental rise is present
There is an oceanic trench though
Very narrow continental shelf
Lots of volcanoes, earthquakes, and mountains
Seafloor
 Passive
 Occur



within a plate area
Broad continental shelves
Has both continental slope and rise
There is an absence of a trench
Seafloor

Continental shelf
 Gentle slope downwards
 Varies in width
 Ends at the shelf – slope break
 Average depth today is 135 m
Seafloor

Continental slope
 Steep decline
 Presence of submarine canyons
 Sediment is transported by gravity at this point


This is a location of turbidity currents/graded bedding
Deposits from the turbidity currents and other gravity flows
accumulate in submarine fans
Seafloor

Continental rise
 Very
gentle slope
 Sediments are transported by gravity
 This is not present in an active margin
 In the passive margins, sediments form series
of overlapping fans and develops the rise
Seafloor
 Deep Ocean Basin


Very dark, cold, intense pressure felt here
Abyssal plain
 Large
flat areas
 Sediments have buried the rugged seafloor

Trenches
 Long,
narrow areas
 Deepest parts of the ocean; associated with volcanoes

Oceanic ridges
 Volcanic
rocks (basaltic)
 Tensional forces/divergent plate boundaries
 Ridges are often offset by transform faults