Transcript Take A Journey to… - Mr. Jensen`s Science

What is inside Earth?
Because Earth’s center is too deep to dig to,
we gather clues by looking at earthquakes,
volcanoes, deep-sea trenches and
mountains.
Physical Structure of the Earth
(5 Layers)
• Lithosphere- rigid outer layer (crust)
• Asthenosphere- solid rock that flows
slowly (like hot asphalt)
• Mesosphere- middle layer (Mantle)
• Outer Core- liquid layer
• Inner Core- solid, very dense
Using Volcanoes and Earthquakes
• Volcano give clues to what is inside the
planet and what it is made of.
• When an earthquake happens, a
seismograph measures the waves all over
the world.
• These waves come at different
frequencies and are “bent”, which tells
scientists that Earth is made of layers that
have different thickness and physical
properties.
Crust
• Continental crust and Oceanic crust
• Continental crust is less dense than
oceanic crust, though it is considerably
thicker; mostly 35 to 40 km versus the
average oceanic thickness of around 7-10
km.
• The oceanic crust consists of a volcanic
lava rock called basalt. The continental
crust is composed mostly of granite.
The Mantle
• Largest layer of the Earth3000 km or1800
miles thick.
• The temperature of the mantle varies from
1600 degrees Fahrenheit at the top to
about 4000 degrees Fahrenheit near the
bottom!
• Plastic like layer.
Outer Core
• The outer core is so hot that the metals in
it are all liquid state.
• The outer core is located about 1800 miles
beneath the crust and is about 1400 miles
thick.
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 about like a liquid, but
are forced to vibrate in place as a solid.
• The inner core is made of nickel and iron.
• The inner core begins about 4000 miles
beneath the crust and is about 800 miles
thick.
Inner Core
• The temperatures may reach 9000
degrees F and the pressures are
45,000,000 pounds per square inch. This
is 3,000,000 times the air pressure at sea
level!
Hot
Hot
Hot!
Continental Drift
• Alfred Wegener’s
theory stated that
Pangaea was once
one continent that
slowly broke apart
and moved to it’s
current position we
now have.
• Wegener called this
the theory of
continental drift – the
movement of
continents.
Pangaea
• In 1912, scientist
Alfred Wegener
proposed the idea of
a supercontinent
named Pangaea.
• He looked at a map
and noticed the
continents could fit
together like a puzzle.
Clues to support Continental Drift
• Wegener found fossils, such as the plant fossil
Glossopteris, in Africa, South America,
Antarctica, and Australia.
• Fossils of the reptile Mesosaurus were found in
Africa and South America. These were
freshwater and land animal, so it is unlikely they
swam across the ocean.
• Wegener also found fossils in cold, icy
Antarctica of organisms that live in warm,
tropical climates.
Plates
Convection Currents
• Convection currents are caused by the
very hot material at the deepest part of the
mantle to rise. While the coldest and
densest material sinks.
Convection Currents
PLATES IN MOTION
• A divergent plate movement occurs when
two plates move away from each other
• Divergent takes place at the boundary of
the oceanic plates and forms new sea
floor. This process is called sea-floor
spreading.