Transcript Land & The Earth

Plate Tectonics
Layers of the Earth
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Crust– 1st layer is solid rock. The thinnest layer.
Lithosphere – The layer that is the crust and the
top of the mantle. Lithos means “rock”.
Asthenosphere – The layer just below the
lithosphere & is part of the upper mantle. Acts
like a plastic, with low density. The layer that
moves the crustal plates.
Mantle – Layer of hot solid rock. The thickest
layer.
Outer Core – Layer made of liquid iron and
nickel. Is responsible for Earth’s electromagnetic
field.
Inner Core – Layer of solid iron and nickel.
Composition of the Layers
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The Earth becomes denser the farther you
go inside.
The crust is made primarily of silicon and
oxygen (silicates) as well as calcium (Ca) &
sodium (Na).
The mantle is primarily iron (Fe),
magnesium (Mg), aluminum (Al), silicon
(Si), and oxygen (O).
Electromagnetic Field
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The Electromagnetic (EM) field is caused due to
the spinning iron and nickel in the outer core.
The EM field protects Earth from harmful
electromagnetic waves in space.
The field also gives Earth its magnetism (North &
South Pole).
The EM field changes each day. It constantly has
to be measured all over Earth.
Form from electrons and protons. Held
together by the magnetic field.
Crust Features
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There are 2 types of crust – Ocean &
Continental.
Ocean crust is most dense and is made
mostly of basalt. Rocks tend to be younger
(no more than 200 million yrs.)
Continental crust is less dense and is made
mostly of granite. Rocks tend to be the
oldest on Earth.
Plate Tectonics
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THEORY - The crust is brittle and can
break. The crust itself is broken into plates.
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These plates move due to convection
currents in the asthenosphere.
A boiling pot illustrates the
convection current in a liquid.
Scientists hypothesize that a
similar action is happening in
the asthenosphere.
The
convection
current
moves the
plates
slowly over
time.
Overview of the actions at plate boundaries
The Theories…..
Various models of
how the
asthenosphere may
be behaving.
Effects of Plate Tectonics
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Earthquakes
Volcanoes
Mountains
Continental Drift (Pangaea)
Hot Spots
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Hawaiian Islands are the
perfect example
The Pacific plate is slowly
moving to the Northwest
Kauai formed first, and as
the plate has moved over
the hot spot, Oahu,
Molokai, Maui, and finally
the big island of Hawaii
have successively formed
Yellowstone is also an
example of a hot spot
Hot Spots are huge plumes of magma
that come from the deep mantle
Proving Plate Tectonics
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Paleomagnetism
Ocean Drilling
Plate Boundary Evidence – including
mapping the ocean floor
Earthquake & Volcanic Activity
SEISMIC WAVES!!
Using Seismic Waves
• These are
devices which
detect seismic
waves.
• The plate is
placed in front
to create the
waves.
• The waves give a
A sledgehammer
profile of the
can
be used to
land.
generate the
seismic waves
Paleomagnetism
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Rocks that align
with the current
magnetic field have
what we call
normal polarity
Rocks that align to
the south pole have
what we call
reverse polarity
The ocean floor is
said to have a
“zebra stripe”
magnetic signal
Ship
The zebra stripes are not visible to the
naked eye, but only to a magnetometer
as it is towed behind a ship
Paleomagnetism
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Yes, the magnetic
signature of the rocks
flip-flops, but the
distances between each
reversal are the same on
either side of the midocean ridge
This allows geologists to
conclude that sea-floor
spreading is equal on
either side of a mid
ocean ridge
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Compare these distances here and
you find that they are identical
Ocean Drilling
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The Deep Sea Drilling Project (DSDP) spent from 1968-1983
drilling 1092 sediment and basalt cores in every ocean on
earth
It was found that fossils in the sediments closest to the ridges
were younger than fossils found further away
This cross section
of the Atlantic
Ocean shows the
topography that the
DSDP found
Sediments near the
ridge were found to
be younger than the
sediments near the
continental margins
Ocean Drilling
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The ocean vessel “GLOMAR CHALLENGER” was the ship that gathered
all the data for the Deep Sea Drilling Project
DSDP has changed into the Ocean Drilling Program (ODP) and
continues to help us understand the oceans even to this day
The Glomar Challenger was
named after the original oceanic
science vessel, Challenger, of
the 1800
Earthquake Patterns
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Well over 95% of all earthquakes occur along the current plate
boundaries
The map shows where earthquakes occur on an annual basis
Do the patterns match up with anything you’ve seen before?
The red dots represent earthquake activity.
What is the relationship with their location and
plate boundaries?
Types of Boundaries
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Convergent – boundaries moving towards
each other.
Divergent – boundaries moving away from
each other.
Transform – boundaries moving side-byside.
Divergent Boundaries
Rio Grande
Rift Valley
Red Sea
East African
Rift Valley
East Pacific
Rise
Mid Atlantic
Ridge
Mid Indian
Ridge
Evidence of
Divergence
in North
America
Rio Grande Gorge – evidence of the
North American plate pulling apart.
Convergent Boundaries
Cascade
Mountains
Appalachian
Mountains
Ural
Mountains
Himalayan
Mountains
Aleutian
Island Arc
Japanese
Island Arc
Philippine
Island Arc
Andes
Mountains
Himalayan Mountains –
picture from space
French Alps
Transform Boundaries
San Andreas
Fault
Continental Drift
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The theory that Earth’s continents move
together and apart due to the moving
crustal plates. Developed by Alfred
Wegener.
The supercontinent when all 7 are together
is called Pangaea.
It take approximately 225 million years for
the continents to come together.
The Evidence
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Continental Jigsaw Puzzle – shorelines & continental
shelves fit together.
Fossils – fossils of animals and plants matched on
different continents that had no way of being
transported across an ocean.
Examples – Glossopteris (fern) found in
Africa, Asia, Australia, India, Antarctica, & South
America; Mesosaurus found in South America &
Africa; Marsupials in Australia & North America
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Rock Types – Mountain ranges that end at a
coastline, then pick up on a different piece of
land.
Example – Appalachians, Mt. range
that starts in the British Isles and then picks up in
Scandinavia, Mts. in South America that begin
again in Africa.
Ancient Climates – Glacial deposits were found in
South America & Africa that were identical;
Evidence of lush forests in the Northern
Hemisphere such as in E. United States, Siberia, &
Europe where it is now cold; South Africa was
situated over the South Pole.
Plates Throughout History
Plates Throughout History
Plates Throughout History
Plates Throughout History
Plates Throughout History
Plates Throughout History
Plates Throughout History
Plates into the Future
Ok, Prove it…
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REMEMBER: The four
main reasons that
scientists give to support
the theory of plate
tectonics
– Earthquake Data
– Ocean Drilling Data
– Hot Spots
– Paleomagnetism