Transcript PLATE TECTONICS

PLATE TECTONICS
GEOLOGY
Chapter 16
JAMES HUTTON
 1727-1797
 Father of Geology
 Edinburgh, Scotland
 Doctor of Medicine
then became a farmer
Can you
believe he
never
married?
Before Hutton there was no Geology
as a science 
Influenced Charles Darwin
Claim to Fame
 Earth is older than 6,000years!
 Not all rocks were deposited in the “Great
Flood”
– Not all sedimentary or flat!
 UNIFORMITARIANISM- present is the
key to the past
– Basis of geology today
ALFRED WEGENER
Father of Plate Tectonics
1880-1930
PLATE TECTONICS
 Born in Germany
 Greenland
meteorologist
 Originated
“radical”
continental drift
theory
CREDENTIALS
Ph.D. in astronomy
Ph.D in meteorology (U of Berlin)
polar atmosphere researcher
published
–Origin of Continents and Oceans
(1915)
EVIDENCE FOR “CONTINENTAL
DRIFT”
Shapes of continents- fit together
Identical fossils separated by
oceans
Same rock layers match across
continents
Glacial evidence in tropics
No one believed him- why not?
Didn’t know
what caused the
plates to move
 tidal force?
Plates “plowed” through ocean
crust- ocean floor is not weak!
 Last photo of Wegner
 Died lost in
Greenland- 1930
 Ridiculed by scientist
NEW (post Wegner)EVIDENCE
1. Sonar (1960’s)-
mapped ocean
floor
– each side of
mid-ocean
ridges match up
• Age of rock
• paleomagnetism
More “new” evidence
 2. Pattern of earthquakes- outline edges of
plates
Maybe Wegner was right!
 “New” theory (1968)
called
PLATE TECTONIC
THEORY
Included:
– “new” way plates
move
– “new” ocean evidence
How do plates move?
 Theory one-
convection currents
 Hot magma rises and
cold magma sinks
creating a current
 Heat comes from
radioactivity
 Plates “ride” on this
current
Convection currents
How do plates move?
 Theory 2- Slab pull/ridge push
– Plates pull themselves down due to density
How do plates move?
 UNSURE!
– Combo of both?
– Wasn’t this the same problem Wegner had?
What is a plate?
Plate tectonics explains so much!
 Location of…
– Volcanoes
– Earthquakes
– Igneous rocks
– Metamorphic rocks
– Mountains
– Folds and faults
PLATE BOUNDARIES
Where plates meet
DIVERGENT
 Move apart
 tensional stress
 fissure eruptions
 basalt
 most under the sea- Mid Ocean Ridge
 some continental- East African rift, Red
Sea,Yellowstone
Divergent boundaries
Fissure eruption
CONVERGENT BOUNDARIES
 Move together
 compressional stress
 3 types
Ocean-ocean
 Volcanoes form on
ocean floor- create
island arcs
 Trenches
 andesite
Japan
Ocean-continental
 Trenches (not as deep)
 composite volcanoes-
pumice, rhyolite
 Volcanoes form on
land
Mt. St. Helens
Continental-continental
 Folded mountains-
non-volcanic!
 Metamorphic rock
Himalayas
 Mt. Everest
TRANSFORM(strike-slip)
 Plates slide past each other
 shearing stress
 shallow earthquakes
San Andreas Fault
Passive Plate boundaries
 Non- active ocean/ cont. boundary
Who gives a schist?
 Predict earthquake areas
 Source for geothermal energy
 Find areas of mineral resources
 Predict future?