Transcript Inside the Earth

If you were lost,
how could a dog help?
A new study says that dogs choose the direction they
relieve themselves based on our planet's magnetic field.
Inside the Earth
How do scientists know?
Earth in General
3 Layers
• Crust
• Mantle
• Core
Diameter
• 12,750 km
Cross Section Diagram
Overview of the Crust
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Solid Basalt and Granite
5-100 km thick
Coolest in temperature
Least dense
2.2-2.9 g/cm3
• Like the “shell of egg,”
is brittle and can break
• Layer we live on
What is the difference between
sediment and bedrock?
Sediment is
Smaller pieces of broken
rock mixed with organic
material and remains
Bedrock is rock
underneath the
accumulated
sediment
Overview of Crust (continued)
• Major changes
 Plate Tectonics
• Minor changes
 Weathering & erosion
 Deposition of sediments
• Two types of Crust
 Oceanic (very dense,
made of basalt)
 Continental (less dense,
made of granite)
Example of minor change
& a bit of New Hampshire folklore
For A. Cleary
Oceanic and Continental Crust
Oceanic Crust
• Mainly Basalt
•Thinnest part of crust ~ 5 km thick
•Density 3.0 g/cm3
• Ocean puddles on top
• Youngest part of crust, new crust
is made here
Continental Crust
• Mainly Granite
•Thickness varies but ~ 30 km thick
• 100 km thick under Himalayans Mts.
•Density 2.7 g/cm3
• Oldest part of crust
Overview of the Mantle
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Like “white” of egg
Hot layer of semi solid rock
Contains more iron, magnesium and calcium than crust
Hotter & denser… temp and pressure increase w/depth
~2900 km thick
Density 3.4 – 5.6 g/cm3
Multiple layers which have
different densities
Upper Mantle and Lower Mantle
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Upper Mantle
~720 km thick
Density 3.4 – 4.4 g/cm3
~1480 C, rock is near
melting
Magma from some
volcanoes can originate
here
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Lower Mantle
~2170 km thick
Density 4.4 – 5.6 g/cm3
~ 2600 C
Higher level of magnesium
& silicon oxides
Overview of the Core
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Mostly iron & nickel, metal
Core is not rock or fire
~3300 km thick
Twice as dense as mantle
Outer Core
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Liquid nickel and iron
2200 km thick
Density 9.9 – 12.2 g/cm3
~3800 C
Inner Core
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Solid nickel and iron
1250 km thick
Density 12.2 – 13.1 g/cm3
~4300 C
The inner core is
solid but hotter than
the outer core; why?
Where does the core get its heat?
• Chunks of material collided and stayed
together, (Heat from these collisions can be on
the order of 10,000 kelvins about 18,000
degrees Fahrenheit).
• Friction, when denser core material sinks
• Decay of radioactive elements, mostly
uranium and thorium according to physicists.
Earth’s Layers
How are the earth’s layers
similar to an egg?
• Shell=crust
• Egg white=mantle
• Yolk=core
Interactions between Layers
Lithosphere
• Includes crust and solid, uppermost part
of the mantle
•Broken into about 19 pieces, these pieces
are called “PLATES”
•The plates move on top of the
Asthenosphere (which is a thin layer of the
upper mantle)
Interactions between Layers
Asthenosphere
• Beneath the lithosphere, in the mantle,
lies a soft, relatively weak region of rock
that flows slowly (like soft plastic or hot
asphalt)
•Convection Currents that drive the
movement of plates happen in the
Asthenosphere
Vocabulary expected to know
Sphere – shaped like a ball
Hemisphere – half of a sphere
Interior – inside
Exterior – outside
Cross Section – diagram that shows a piece “cut
out,” so you can see the inside
Molten – melted, usually referring to material
that melts at very HIGH temperature
Vocabulary expected to know
*Lava – melted rock touching atmosphere
*Magma – melted rock below the crust
Tectonic Plates – broken pieces of the
lithosphere
Tectonic Plates
• Earth’s crust is broken into about 19 pieces
• These plates move on top of the
asthenosphere (thin layer of the upper mantle)