Download Continental Drift and Sea Floor Spreading

Earth‘s
Layers
Anticipation guide
• Convergent boundaries occur where
plates move apart
• The outer core is liquid and the inner core
is solid
• Earthquakes generate seismic waves
• The Richter scale measures the intensity
of earthquakes
• The lithosphere is found deep in the
mantle
VA SOL
• ES.7 The student will investigate and
understand geologic processes including
plate tectonics. Key concepts include
• geologic processes and their resulting
features; and
• tectonic processes.
Enduring Understanding
• The core, mantle, and crust of the Earth
are dynamic systems that are constantly in
motion.
The Earth is divided
into layers by
density.
As the Earth solidified during the formation of
the solar system elements with higher density
were drawn toward the center of the Earth by
gravity.
Earth’s Interior
• It has a pressure of 3.2-4 million times that of
the surface and this pressure keeps the metals
in solid state
Earth’s Interior
• Inner Core is solid and is made of the densest
material.
• It is believed to be comprised of iron and nickel
Earth’s Core
The core of the
Earth is composed
of the elements
Nickel and Iron,
it makes up 19
percent of
Earth's volume
and 33 percent
of Earth's mass.
The core of the Earth
is divided into two
parts, the Inner Core
and the Outer Core.
The Outer Core is liquid metal and the
Inner Core is solid due to the pressure
from the weight of
all the matter in
the Mantle and Crust.
The Inner Core is 5,150 km deep with a
temperature of 5000 degrees celsius.
The Outer Core is 2,900 km deep and is
from 2200 - 5000 degrees Celsius getting
hotter moving toward the center of the Earth.
The largest layer of the Earth is the Mantle.
Earth's Mantle makes up 80 percent of Earth's
volume and is made up of silicon, oxygen, and
magnesium.
The crust of the Earth is a very thin solid
outer layer of the Earth.
It is only 1 percent
of the volume
of the Earth.
Earth’s Crust
• Oceanic crust is comprised mainly of the
rock basalt
• Continental crust is comprised mainly of
the rock granite
Earth’s Crust
• Continental crust makes up the land masses.
This thicker, less dense material allows the
continents to rise above sea level and remain
dry for very long periods
The Crust and the upper part of the Mantle
together make up the Lithosphere.
Lithosphere
Crust
Upper Mantle
The Lithosphere is about 100km thick and is
broken up into several solid plates that are
moved by convection currents within the
mantle.
The Asthenosphere
is a plastic layer
near the bottom of
the Lithosphere.
Earth’s Interior
• Most of the mantle is in solid or plastic form
(think silly putty)
As the very hot core heats the material in
the Mantle it causes the material to move in
a circular pattern. The mantle material heats
up and rises and then cools and sinks. This
circular pattern of movement within the
mantle (called a convection current) pushes
the lithospheric plates as they float. The
movement and interaction of these plates
causes most of the large scale changes on
Earth's surface.
Earth’s Interior
• The motion of the liquid metals in the inner
core is what generates the Earth’s magnetic
field
Draw, color, and label these in your notes…
Next class you will have a quiz on the layers of the
Earth. You need to know the following:
Density increases: Crust  Mantle  Core
Core is divided into molten outer core and solid
inner core.
Core is made of iron and nickel.
Lithosphere is the crust and upper mantle.
Asthenosphere is plastic (like playdough) and is
part of the mantle.
Both definitions and diagrams will be on this quiz.
Continental Drift and Sea
Floor Spreading
Anticipation guide
• There are 4 main layers of the Earth
• Continental drift is a theory explaining how
continents move over time
• Mountains are created in random places
on earth by random forces
• All volcanoes are created by plates
colliding
• The oldest crust on Earth is found under
the ocean
VA SOL
• SOL 7 The student will investigate and
understand geologic processes…... Key
concepts include
• A. tectonic processes (subduction, rifting
and sea floor spreading, and continental
collision).
Objective
Outline the history of plate tectonics to
include continental drift and sea-floor
spreading.
Explain how the lithosphere is divided into
plates that are in motion (compression,
tension, and shearing) with respect to one
another (because of convection currents in
the mantle).
Enduring Understanding
• The core, mantle, and crust of the Earth
are dynamic systems that are constantly in
motion.
Continental Drift
• Throughout the typical human lifespan the
Earth’s surface appears to remain relatively
unchanged.
Continental Drift
• On the geologic timescale the surface is
constantly moving back and forth swallowing
and creating oceans and continental mass as
it goes
Continental Drift
• Early mapmakers were the first to suggest that
the continents appear to have fit together at
one time
Continental Drift
• Alfred Wegener a German scientist was the
first to propose this theory to the scientific
community in the early 1900’s
Continental Drift
• Pangea was the name for this supercontinent
that began to break up about 200 million
years ago
Continental Drift
• Wegener’s theories were not accepted at the
time because his explanations were not
supported by physicists
Continental Drift
• His explanation for movement was that the
continents plowed through the seafloor crust
like moving islands
Continental Drift
• His explanation for the reason why the
continents moved was the spinning of the
earth
Evidence of Continental Drift
• Although his explanations for the reason the
continents drifted were incorrect there was still
convincing evidence that they were indeed
once together.
Evidence of Continental Drift
• Rock formations in the Appalachian
Mountains matched up with ones in
Greenland.
Evidence of Continental Drift
• Fossil evidence found in South America and
Africa were especially strong
Evidence of Continental Drift
• Bones from the Mesosaurus and
Kannemeyerid were found in the same rock
formations in Brazil and Chad
Evidence of Continental Drift
• Even glacial striations from ancient Ice ages
were found to match perfectly
Evidence of Continental Drift
• Climatic evidence found that there were coal
deposits in Antarctica suggesting that
continent was at one time much closer to the
equator
Sea Floor Spreading
• Alfred Wegener died in 1930 never having
seen the acceptance of his controversial
theory
Sea Floor Spreading
• In the early 1960’s new evidence revealed
the process on how the continents could
indeed move
Sea Floor Spreading
• Advances in sonar technology in the 1940’s
and 50’s allowed us to begin to accurately
map the seafloor
Sea Floor Spreading
• This evidence proved that the seafloor was not
flat and featureless as once thought. Vast
underwater mountain chains and deep trenches
were discovered.
Sea Floor Spreading
• Earthquakes and volcanic activity was prevalent
in certain parts and missing in others
Sea Floor Spreading
• The ocean floor was found to be much
younger than the continental crust
Sea Floor Spreading
• The thickness of the layers of sediments
increased with the distance on either side of the
ocean ridges
Paleomagnetism
• Once scientists were able to bring sea floor
samples to the surface they were able to
determine that a record of the seafloor was
being kept by Earth’s magnetic field
Paleomagnetism
• Paleomagnetism is the study of this magnetic
record using data gathered from iron-bearing
minerals
Paleomagnetism
• The magnetic records for the seafloor on either
side of the mid-ocean ridges matched perfectly
showing that the seafloor was growing outward
from the ridges in both directions
Paleomagnetism
• Isochron is a line on a map that connects
points that are the same age
Paleomagnetism
• Once scientists had compiled all the
topographic, sedimentary, age and magnetic
data an American scientist named Harry Hess
proposed a theory that could explain the
observations
Paleomagnetism
• Sea Floor Spreading states that new ocean
crust is formed at the ocean ridges, moves
outward in both directions, then destroyed at
the deep sea trenches.