Download crust - River Dell Regional School District

CH 17: EARTH
STRUCTURE
GEOPHYSICAL
The Layers of the Earth
© Copyright 2006. M. J. Krech. All rights reserved.
THE FOUR LAYERS
The Earth is composed of
four different layers. The
crust is the layer that you live
on, and it is the most widely
studied and understood.
The mantle is much hotter and
has the ability to flow.
The outer core and inner core
are even hotter with
pressures so great you would
be squeezed into a ball
smaller than a marble if you
were able to go to the
center of the Earth!
EARTH LAYERS
• The Earth is divided into four main
layers.
*Inner Core
*Outer Core
*Mantle
*Crust
- lithosphere
-asthenosphere
THE CRUST
*The Earth’s crust is like
the skin of an apple. It
is very thin compared to
the other three layers.
*The crust makes up 1%
of the Earth.
* The crust is made of the
lightest matter and the
core consists of heavy
metals
THE CRUST
The crust is only about
3-5 miles (8 kilometers)
thick under the
oceans (oceanic
crust) and about 25
miles (32 kilometers)
thick under the
continents
(continental crust).
THE CRUST
The crust is composed of two rocks. The
continental crust is mostly granite. The oceanic
crust is basalt. Basalt is much denser than the
granite. Because of this the less dense
continents ride on the denser oceanic plates.
THE LITHOSPHERE
The crust and the upper layer of the mantle
together make up a zone of rigid, brittle rock called
the Lithosphere. This rock is divided into fragments
plate.
WHAT IS THE THEORY OF PLATE
TECTONICS?
• Tectonic plates: a theory that
giant plates of rock are moving
slowly across Earth’s surface
THE LITHOSPHERIC PLATES
The crust and upper portion of mantel
(lithosphere) of the Earth is broken into many
pieces called plates. The plates "float" on the
soft, semi-rigid asthenosphere.
ASTHENOSPHERE
The plates move along the
soft mantle which is the layer
located below the crust.
LITHOSPHERE AND ASTHENOSPHERE
• The lithosphere (litho:rock; sphere:layer) is the
strong, upper 100 km of the Earth.
• The lithosphere is the tectonic plate we talk about in
plate tectonics.
• The asthenosphere (a:without; stheno:strength) is
the weak and easily deformed layer of the Earth
that acts as a “lubricant” for the tectonic plates to
slide over.
• The asthenosphere extends from 100 km depth to
660 km beneath the Earth's surface.
• Beneath the asthenosphere is the mesosphere,
another strong layer.
The Asthenosphere
The asthenosphere is the
semi-rigid part of the
middle mantle that flows
like hot asphalt under a
heavy
weight.
PLATE TECHTONICS
• The plates move along smoothly
but sometimes they get stuck and
pressure builds up.
EARTHQUAKES
The pressure builds and
causes an Earthquake as
rocks break and crack.
San Francisco City Hall after the 1906
Earthquake. (from Steinbrugge
Collection of the UC Berkeley
Earthquake Engineering Research
Center)
THE MANTLE
• The mantle is the
layer below the
crust.
• The mantle is the
largest layer of the
Earth.
• The mantle is
divided into two
regions: the upper
and lower sections.
MANTLE
• The movement of the
mantle create the
movement of the Earth’s
plates.
• It is made of hot, dense
rock. The rock in the
mantle flows like asphalt
because of the
temperature differences
found in the mantle.
CONVECTION CURRENTS
The middle mantle
"flows" because of
convection currents.
Convection currents
are caused by the
very hot material at
the deepest part of
the mantle rising, then
cooling and sinking
again --repeating this
cycle over and over.
CONVECTION CURRENTS
The next time you heat
anything like soup or water in a
pan you can watch the
convection currents move
in the liquid.
When the convection currents
flow in the asthenosphere
they also move the crust. The
crust gets a free ride with these
currents, like the cork in this
illustration.
CORE
•The core of the Earth is
much like a ball of very
hot metals. The inner core
is surrounded by a fluid
iron outer core.
CORE
OUTER CORE
* The core of the
Earth is like a ball
of very hot metals.
* The outer core is
liquid.
* The outer core is
made up of iron and
is very dense.
INNER CORE
* The inner core of
the Earth has
temperatures and
pressures so great
that the metals are
squeezed together
and are not able to
move.
* The inner core is a
solid.
REVIEW
1) What are the four layers of the Earth?
2) The Earth’s crust is very ______?
3) The mantle is the largest layer of the Earth? True or
False
4) Is the Outer Core a liquid or a solid?
ANSWERS!
1) Crust, Mantle, Outer Core, Inner Core
2) Thin
3) True
4) Liquid
WHY DO WE NEED TO KNOW THIS?
Earth has layered structures with solid
rock at the surface and partly liquid
rock material below.
When scientists understand the Earth’s
structure, they can help predict when
a geyser or a volcano will erupt, or
how a river will change course over
time.
DID YOU KNOW?
In many parts of the world, columns of
steaming hot water can be found
shooting up from the Earth’s surface.
These boiling fountains are known as
geysers!!!
Jim Bridger was
Quoted as saying
the geysers are so hot
that meat is readily
cooked in them!!
DID YOU KNOW?
Yellowstone National Park in
Wyoming is well known for its
numerous geysers and hot springs.
OKAY, BACK TO GEYSERS…
What do geysers tell us about the
Earth’s interior?
GEYSERS TELL US
THE EARTH’S INTERIOR IS…
HOT, HOT, HOT!!!
THE DEEPER INTO THE EARTH’S
INTERIOR YOU GO, THE
HOTTER IT GETS!!!
SO, IS IT HOTTER AT THE EARTH’S
CORE, OR THE EARTH’S CRUST?
- CORE, MANTEL, OR CRUST?
LET’S THINK…
Where would be the best place on Earth’s surface to
try to drill a hole all the way to the mantle?
(Remember, the mantle is the thickest layer between
the crust and the outer core.)
A. The ocean floor
B. The top of a mountain
THE OCEAN FLOOR
The crust is thinner under the ocean, making it easier
to drill a hole to the mantle.
Why would it be most difficult to drill a hole to the
mantle starting at the top of a mountain?
ANSWER
The crust is thickest at the
top of a mountain.
(Think of it this way… if you start drilling at the top of a
mountain you must drill all the way down through the
mountain just to get to ground level. Then, you have
to continue drilling until you hit the ocean floor. Only
then does the actual drilling below the Earth’s crust
begin.
QUESTION
What layer of the earth’s core is liquid?
ANSWER
Outer core!!!
The heat there is hot enough to
melt rock, but the pressure is not
great enough to make a solid
mass, as it is in the inner core.
UP NEXT!!!
Next, we’ll study plate tectonics, volcanoes and
earthquakes!!!