Download Crust - SharpSchool

1.1 Earth has several Layers
 Denser
material sinks
 Less dense material rises to the
top
• Crust: Thick layer of cool rock,
surrounding earth. There are 2 types:
oceanic and continental
• Mantle: Earth’s thickest layer, 1700
miles thick, hot rock, less dense than
core
• Outer Core: Layer of liquid metal that
surrounds inner core
• Inner Core: Ball of solid, hot metal
 Lithosphere:
most rigid of the
layers, contains the outermost
part of the mantle, and the
crust
 Asthenosphere: layer of
hotter, softer rock in the upper
mantle


Tectonic plates fit together like a jigsaw
puzzle
Contain both continental crust and oceanic
crust
1.2 Continents Change over Time
 Continental
Drift
 Hypothesis proposed by Alfred
Wegener in 1912
 Earth’s continents were once
joined in a single landmass
and gradually moved apart.
Fossils: mesosaurus found in South
America & Western Africa – not found
anywhere else!
 Climate: evidence of change: Warm
weather plants in Greenland, glacial
evidence in South Africa
 Geology: rocks from Brazil match
those of Western Africa, Limestone of
Appalachian mountains matches
Scotland’s highlands

 Pangaea:
Greek meaning “all
lands”
 Giant continent that reached
from pole to pole and covered
area where Africa lies today
 In
the mid 1900’s scientists
proved that tectonic plates
move.
 Built upon Wegener’s ideas.

Mid Ocean Ridges: huge underwater
mountain ranges
◦ Sea Floor Spreading – ridges form along
cracks in the crust, molten rock rises
through the cracks making new crust
◦ Age of sea floor – sea floor is youngest at
the ridges, older farther away
◦ Ocean trenches – deep canyons where the
sea floor is sinking into asthenosphere.


Convection: energy
transfer by the
movement of
material
Convection current:
sinking and rising
motion that
transfers heat in a
material
Convection

Theory of plate tectonics: Earth’s lithosphere
is made of huge plates that move over the
surface of the earth.
1.3: Plates move apart
 Divergent
boundaries:
occurs
where plates move apart – most
are found in the ocean
 Convergent boundaries:
occurs where plates push together
 Transform boundaries:
occurs where plates scrape past
each other


AKA spreading centers
Rift valley: deep valley formed as tectonic
plates move apart, as a long a mid-ocean
ridge


Mid-ocean ridges are the longest chains of
mountains on Earth
Mid-Atlantic ridge world’s longest mountain
range


Earth’s magnetic poles switch places, called
magnetic reversals
How stuff works


Like the sea floor, continents can split apart
at a divergent boundary
Great Rift Valley

View plate boundaries


Hot spot: heated rock rising in thin columns
from the Earth’s mantle.
Hawaiian islands
1.4: Plates converge of scrape past each other
 Subduction:
when one plate
sinks beneath another
 Oceanic crust: crust under
ocean floor - more dense
 Continental crust: crust
forming the continents – less
dense
 Two
plates carrying continental
crust push together
 Same density, neither one skins
 Rocks crumple and fold to form
mountains
 Examples: European Alps,
Himalaya



One plate of oceanic crust subducts (sinks)
beneath another plate of oceanic crust
Older plate is colder and denser, and sinks
below younger plate
Creates two features:
◦ Deep ocean trenches – deep canyons in ocean floor
example: mariana trench
◦ Island arcs – chains of volcanic islands that form on
the top plate parallel to trench. Example: Japanese
islands
Ocean crust sinks under continental
crust
 Oceanic crust is colder and denser
than continental crust
 Features created:
◦ Deep ocean trenches – can cause
underwater earthquakes
◦ Coastal Mountains – Examples:
Cascade Mountains


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Transform boundary: plates scrape past each
other in opposite direction
Crust is neither created nor destroyed
Example: San Andreas Fault, San Francisco
California
The plates lithosphere has been in
motion for millions of years
 By studying rock layers geologists can
uncover the history of any region.
 Plate tectonics gives scientists a way
to study and predict geologic events
such as earthquakes and volcanic
activity
