Transcript Earth`s Structure

Earth’s Structure
The layers of Earth
•
Earth is divided into 3
layers based on
chemical composition.
1) Core: Dense metallic
center, made up of
mainly metal iron.
2) Mantle: Liquid middle
layer made up of silicon,
oxygen and
magnesium.
3) Crust: The solid outer
layer made up of silicon,
oxygen and aluminum.
Continental and Oceanic Crust
•
There are two types of
crust:
1. Continental: is thicker
2. Oceanic: is thinner and
heavier.
• Compared to the other
layers, both types of
crust are rocky, thin and
fractured.
The Physical Structure of Earth
•
Earth is divided into five layers
based on physical properties.
1.
2.
3.
4.
5.
Lithosphere
Asthenosphere
Mesosphere
Outer core
Inner core
Lithosphere
1. Lithosphere:
cool rigid layer,
made up of the crust
and upper layer of
the mantle.
Lithosphere is
divided into pieces
called tectonic
plates.
Asthenosphere
2. Asthenosphere
• Below the lithosphere.
• Made up of slow
flowing solid rock.
• The moving rock
allows for tectonic
plates to move.
Physical Structure cont.
• 3. Mesosphere: Slow
flowing layer beneath
the Asthenosphere
• 4. Outer core: Layer of
liquid Iron and Nickel.
• 5. Inner core: Solid iron
and nickel, temperature
is estimated to be
between 4000ºC to
5000ºC
Mapping Earth’s Interior
• How can we know so
much about Earth’s
interior if no one has ever
drilled through the crust?
• Earthquakes produce
seismic waves, and travel
thru materials at different
speeds.
• Scientists use these
waves to determine the
density of each of Earth's
layers
Continental Drift
• In the 1900’s,Scientist
Alfred Wagner, viewed
the continents as puzzle
pieces.
• Had a hypothesis that our
continents used to be one
large continent.
• He named his hypothesis
the Continental Drift
Theory.
Evidence for Continental Drift
• Fossils of same plant
can be found on
continents that are far
from each other.
• Location of mountain
ranges with similar
rocks show a pattern.
The Breakup of Pangaea
• A single continent
Pangaea (many
thousands of years ago).
• Split into two continents –
Laurasia and Gondwana
(thousands of years ago).
• Split into today's
continents.
• Continents sometimes
collided, forming
mountain ranges and
volcanoes.
Sea-Floor Spreading.
• When Wagner introduced his hypothesis, many
scientists did not accept it because the strength
needed to move Earth’s crust seemed
impossible.
• In the 1960’s Scientist studying the ocean floor
discovered identical patterns of magnetism on
both sides of the mid ocean ridge.
• This was proof that continental drift was
possible.
Sea-Floor Spreading cont.
• At a mid-ocean ridge, magma rises
through fractures in the sea floor.
• As the magma cools it forms new sea
floor.
• As this continues to happen, new floor is
made and older floor is pushed away from
the fracture.
• Sea-floor spreading was proven to cause
continents to move.