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Dynamic
Earth
Ms. Susinno
• In 1915, the German
geologist and meteorologist
Alfred Wegener first
proposed the theory of
continental drift which
stated that continents were
all connected at one point in
Earth’s history.
• The theory of Continental
drift led to the currently
accepted theory of plate
tectonics.
* The continents never
actually looked like a
chicken, but it’s funny!
Theory of Continental Drift
Despite publishing a large body of compelling fossil and rock evidence
(GEOLOGIC EVIDENCE) for his theory between 1912 and 1929, the
theory of Continental Drift was rejected by most other scientists because the
theory failed to provide a mechanism for HOW the continents moved. Poor
Alfred: https://youtu.be/T1-cES1Ekto
Plate Tectonics:
The theory that the outer rigid layer of the earth (the lithosphere) is
divided into a couple of dozen "plates" that move around across the
earth's surface relative to each other. Evidence suggests that the plates
are moving atop convection cells in the asthenosphere.
Click to see plate boundaries in action!
http://www.wwnorton.com/college/geo/egeo2/content/animations/2_1.htm
Earth’s
layers
• The
properties of
the inner
Earth are
inferred with
evidence from
Earthquake
waves
• We have
never
penetrated
the crust so
we have very
little direct
evidence of
the Earth’s
interior!
https://youtu.be/ZkaDvzGGspM
http://www.regentsearth.com/Illustrated%20ESRT/Page%2010%20(Earth's%20Interior)/Page%2010%20index.ht m
Earth’s layErs:
The asthenosphere is the layer of the Earth that lies below the lithosphere.
This Plastic Mantle contains rock that is partially melted and slowly
moving below the lithospheric plates. This allows the tectonic plates of the
lithosphere to move around on the Earth's surface by “riding" on the
convection cells in the asthenosphere!
https://ees.as.uky.edu/sites/default/files/elearning/module06swf.swf
Marie Tharp (July 30,
1920 - August 23, 2006)
created the first scientific
map of the entire ocean
floor.
The
Sea
Floor
Harry Hess (May 24, 1906 –
August 25, 1969) considered a
founding father of Plate
Tectonics, found evidence for sea
floor spreading
Mid ocean ridges
A mid-ocean ridge is a type underwater, volcanic mountain ridge. This
uplifting of the ocean floor occurs when
convection currents rise in the mantle
beneath the oceanic crust. Lava cools to
magma and creates a ridge where two
plates diverge. The sea floor is made of
basalt.
http://earthguide.ucsd.edu/eoc/teachers/t_tectonics/p_seafloorspreading.html
Sea floor Spreading
• Iron in the sea
floor lines up with
Magnetic North.
• Magnetic North
changes throughout
Earth’s History
• The ocean floor
keeps a tangible
record of polarity
Sea Floor
SpreadingEvidence that provided the mechanism
(convection cells in the asthenosphere)
for plate tectonics that Wegener was
lacking in his theory.
http://study.com/academy/lesson/sea-floor-spreading-and-polar-reversal.html
Plate boundaries
http://www.wwnorton.com/college/geo/egeo2/content/animations/2_1.htm
Types of
Faults
Hanging
wall
Hanging
Wall
Foot Wall
Foot Wall
Earthquake Waves
P Waves- Primary Wavestravel the fastest, first to arrive. Also
called push-pull waves because
this describes the grounds motion as
the waves pass. Travel through
solids, liquids or gas.
S Waves- Secondary WavesTravel slower than P waves. Also
called Side to Side waves because
this describes their motion. Only
travel through solids.
Surface Waves- includes both
push-pull motion and side to side
motion. Cause the most damage
because they travel along the
surface.
Seismometers are instruments that
measure motion of the ground, including
those of seismic waves generated by
earthquakes, volcanic eruptions, and other
ground shaking events
Seismogram:
The Richter magnitude scale (often shortened to Richter scale) is the most
common standard of measurement for earthquakes. It was invented in 1935 by
Charles F. Richter of the California Institute of Technology as a mathematical
device to compare the size of earthquakes. The Richter scale is used to rate
the magnitude of an earthquake, that is the amount of energy released during
an earthquake.
The Richter scale
doesn't measure
quake damage
The Mercalli intensity scale is a
seismic scale used for measuring
the intensity of an earthquake by
taking into account, the damage
reported at each location
Identify the earthquake
intensity of each
observation made at
different locations.
The shadow zone is
the area of the earth
from angular
distances of 104 to
140 degrees from a
given earthquake
that does not receive
any direct P waves.
The shadow
zone results from S
waves being stopped
entirely by the liquid
core and P waves
being bent
(refracted) by the
liquid core.
http://www.classzone.com/books/earth_science/terc/content/visualizations/es1009/es1009page01.cfm
Real-Time
Earthquake
Map
http://ds.iris.edu/seismon/
http://ds.iris.edu/seismon/swaves/
Earthquake safety
The End
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