Download Plate Tectonics 1

Plate Tectonics 1
Structure and Physical
Properties of Earth’s
Interior
Continental Drift vs. Plate Tectonics
What was the Evidence
Supporting Continental Drift?
Alfred Wegner came up with the Continental
Drift Hypothesis. His 5 pieces of
evidence were:
1) Continents seemed to fit together
2) Similar fossils on each continent
3) Rocks matched (age and composition)
4) Glacial evidence – striations (scratches in
rocks matched) + deposits
5) Climate evidence – due to types of fossils
found, coal deposits… continents have
been in different locations on Earth’s
surface
Structure and Physical Properties of
Earth’s Interior
• Lithosphere
– Continental Crust
– Oceanic Crust
•
•
•
•
MOHO
Mantle
Outer Core
Inner Core
30 km
Crust
Rocky
What is the lithosphere?
The Lithosphere is the crust and uppermost part
of the mantle
•It is cool, rigid
and solid layer
broken into plates
that move
•Oceanic crust is
mostly basalt
•Continental crust
is composed of
granite
granite
basalt
What are lithospheric Plates?
• Earth’s surface consists of moving pieces
of crust called lithospheric plates
• Lithospheric plates
– Have both continental and oceanic crust
• Plate Tectonics is the study of formation,
destruction and movement of these plates
Earth’s Crust
• Composed of THE BIG EIGHT - the eight most
abundant elements in the earth’s crust
– oxygen, silicon, aluminum, calcium, iron, sodium,
potassium, magnesium
Continental Crust
Oceanic Crust
Thickness
Average 32 km
Less than 10 km
Composition
Si, O, Al, Ca, Na, K
Si, O, Fe, Mg
(mafic)
(granitic/felsic)
Location
Crust beneath the
continents
Crust beneath
the oceans
Density
Less dense than
oceanic crust
More dense than
continental
crust
The Continental Crust
• Average Thickness is 25 miles
• May exceed 40 miles in mountainous
regions
• Granitic Rocks-LOWER density
• Up to 4 Billion years old
The Oceanic Crust
• Average Thickness is 5 miles
• Basaltic Rock - HIGHER density
• Younger than 180 million years old
– (younger than continental crust)
MOHO
• Mohorivicic Discontinuity
– The boundary between the crust and Mantle
The Mantle
• Consists of the Asthenosphere (upper
mantle) and Mesosphere (lower mantle)
• Below the crust to a depth of 1800 miles
• Composition of the upper mantle is igneous
rock peridotite
– (changes at a greater depth)
The Asthenosphere
• Beneath the lithosphere about 130-160 km
thick
• Upper part of the mantle to a depth of about
660 km
• Soft, weak layer easily deformed
• Composed of hot molten material that can
flow easily
The Mesosphere
• Depth at 660-2900 km beneath Earth’s
surface
• More rigid layer
• Rocks are very hot and capable of a gradual
flow
The Outer Core
• Liquid layer composed of a nickel & iron
alloy (very high density)
• 2270 km (1410 miles) thick
• Convective flow generates Earth’s magnetic
field
The Inner Core
• Sphere with a radius of 1216 km (754
miles)
• Has properties consistent with solids
• Composed of mostly Iron (and Nickel)
Where is the lithosphere
and the Asthenosphere?
Review
What is plate tectonics?
What are the lithospheric plates?
What do lithospheric plates consist of?
What are the 5 types of evidence supporting
the theory of continental drift/ plate
tectonics?
Review
What are the four layers of the earth?
What is the state (consistency)/composition of
each layer?
Review
What is oceanic crust composed of?
What is continental crust composed of?
Which one is thicker?
What are the similarities and differences of
the lithosphere and the asthenosphere?