Transcript Plate tectonics 2 - PAMS

PLATE TECTONIC PUZZLE
1.
2.
3.
4.
Reconstruct Pangaea
What evidence led to your
conclusion?
What landmasses logically fit
together?
What other evidence led you to
believe the continents fit
together?
Early Earth and Plate Tectonics
The early Earth & Plate Tectonics
The Earth’s Drifting Continents
German scientist Alfred Wegener, 1900’s proposed
the Theory of Continental Drift… he was not the
only one to do this… he was able to collect
evidence though
Evidence
1. Glossopteris (gymnosperm… seed fern), located
in 250 myo rocks, were found in South Africa,
Australia, India, and Antarctica
2. Antarctica once had a warmer climate
3. Rock formations and deposits lined up on several
continents
4. Evidence of glaciers in now warm climates
The Evidence
Same fossils on
different continents
Same species of plants and rock
formations on different
continents
The Real Issue………..
How could the continents move through the solid
rock bottoms of the oceans?
In the 1950’s, scientists using better instruments
found underwater mountain chains with rift valleys
in their centers
Midocean ridge
Earth’s Spreading Ocean Floor
A. Mid-ocean ridges form the single largest
mountain range in the world (under the oceans)
B. 80,000 km long and 3 km high
C. Lava erupts to form new sea floor
D. As it spreads it takes continents with it
This explained the mechanism for continental drift!
Seafloor Spreading
Iceland, "the land of fire and ice", is being split by an
oceanic ridge that surfaces to create an oceanic island in the
North Atlantic Ocean.
Interesting Iceland
1.
2.
Slightly smaller than Kentucky
3.
Natural hazards: Earthquakes and volcanic activity;
avalanches
4.
Environment issues: Water pollution from fertilizer
runoff; inadequate wastewater treatment
5.
More land covered by glaciers than in all of continental
Europe
6.
Number of volcanoes: 43
Average temperature is 11°C (52°F) in July and -1°C
(30°F) in January
Magnetic stripes on the ocean floor were further
evidence that the sea floor was spreading. The
patterns are identical on each side of the ridge
Closer examination shows that the magnetic
poles have reversed themselves anywhere from
9-2,000 times in the past 3.5 million years…
depends on the strength of the field tested.
Pole Reversal
The magnetic pole is currently 966 kilometers (600
miles) from the geographic one.
The magnetic pole lies in the Arctic Ocean… it is
currently migrating toward Siberia
Earths
Magnetic Field
LITHOSPHERIC PLATES
Thousands protest against Global
Warming!!!
If the ocean floor is being created, is the
Earth getting bigger?... No
• Rock in the ocean is relatively young
• Ocean floor is being destroyed in trenches in a
process called subduction
• The denser ocean crust is pushed downward into
the mantle and melts
• It is a cycle… some goes down and some goes up
Some goes down
Some comes up
The Earth’s Moving Plates
The Theory of Plate Tectonics, which links continental
drift and seafloor spreading, explains how the Earth
has evolved over time. It helps to explain the
formation, movement, collisions, and destruction of
the Earth’s crust
PLATE TECTONICS
Lithospheric Plates
 There are seven major plates, Pacific, North
American, South American, Eurasian, African,
Indo-Australian, and Antarctic
 There are many small plates, Caribbean, Arabian
are examples
 Each plate moves at a different speed and
direction
 Some are oceanic and some are continental
ACTIVITY
1. Label & color the seven major plates
2. Answer the questions on the back
Sand Art… Relax while you work 
Moody Slide… hopefully it will work
Will the Earth Continue to Change?
The Floating Crust
Isostasy is the balance between the downward force
of the crust and the upward force of the mantle
Plate Boundaries
Divergent boundary- plates moving apart
C to C forms a rift valley that fills in w/ seawater:
Iceland or African Rift Valley
O to O forms a mid-ocean ridge: Mid-Atlantic Ridge
Convergent boundaryplates that are moving
together
Collision of
Continental and Oceanic Plates =
Trench and Volcanic Arc
Pacific Coast, Washington State
Collision of
2 Continental Plates =
Mountain Range
Himalayas (India)
Collision of
2 Oceanic Plates = Trench and Island Arc
Transform boundary, slip-strike,
lateral faults- plates slide past one
another resulting in earthquakes
San Andreas
Fault is this
type… and no
CA will not fall
into the ocean….
LA will be a
suburb of San
Francisco
Plate Motion
The power of the convection currents in the
mantle is thought to be the force that moves the
plates
The Earth’s Changing Surface
Stress is what causes the surface of the Earth to
change
As the rocks undergo stress, they slowly change
shape and volume
They also move up and down or sideways
Types of Stresses
 Compression squeezes the rock (Convergent)
 Tension causes the rocks to stretch out over a larger
area (Divergent)
 Shearing of the rock causes it to twist or tear
(Transform)
Faulting
A break or a crack along which
rocks move
Earthquakes are sometimes
along these faults
If the rock above the fault moves down, the fault
is termed normal (tension), whereas if the rock
above the fault moves up, the fault is termed
reverse (Compression)
Faulted Mountains and
Valleys
 Mountains formed when
there are many normal
faults in one area
 Blocks of rock are
uplifted
 Valleys may form when
the block of land
between 2 normal faults
slides downward
Folded Mountains
• When stress is applied to the rock formation and
it bends but doesn’t break
• Forms an anticline which is an upward fold and a
syncline which is a downward fold
Anticline v. Syncline
Synclines Sink
Volcanic Mountains
Single peak mountains
formed from
volcanoes
Yellowstone
Yellowstone Super Volcano Alert