Download indirect evidence

Earth’s Interior
• Earth’s surface has been lifted up, pushed down, bent, and broken
therefore it looks much different today than it did millions of years
ago.
• Can we dig to the center of Earth? Explain why it is or is not possible.
No way! The extreme conditions within Earth’s interior prevent
scientists from exploring.
Exploring Inside Earth
Geologist use two main types of evidence to learn about Earth’s interior:
direct evidence from rock samples and indirect evidence from seismic
waves.
Direct Evidence
Indirect Evidence
• Geologist drill holes that bring
up samples of rock
• From the samples they make
inferences about conditions
deep inside Earth, where these
rocks were formed.
• Geologist also study rocks that
blast up to the surface from
deep within Earth
• Earthquakes (EQ) produce
seismic waves that scientists
record to see how they travel
through Earth’s interior.
• The speed of the waves and
paths they take reveal the
structure of the planet.
• Use this data we’ve discovered
the Earth is made of layers.
Earth’s Layers
•
Four main layers of the Earth:
Inner Core, Outer Core, Mantle,
Crust.
•
Each layer has a different size,
composition, temperature, and
pressure.
Crust
• Outermost layer covering Earth
• Makes up only 1% of Earth’s volume
• Two types of crust
1. Continental
 25 to 70 km thick
 buoyant (less dense
than oceanic crust)
2. Oceanic
 5 to 10 km thick
 dense (sinks under
continental crust)
-Curst Continued• Temperature- range from
200 C to 400 C
• Composed of aluminosilicates (igneous,
metamorphic, and
sedimentary rocks).
 70% of Earth’s surface is
covered in oceans
Mantle
Scientists divided mantle into layers based on physical characteristics of
those layers.
Lithosphere
• Uppermost part of mantle that is rigid and very similar to crust
Asthenosphere
• This material is hotter and under increasing pressure  less rigid
• This layer of mantle can bend like plastic but still considered a solid
Lower Mantle
• Solid material
-Mantle Continued•
The mantle is between crust and outer
core
• Entire mantle is 2, 900 km thick
• Temperature
• 500 to 900 C at the upper boundary
• Up to 4,000 C at the lower boundary
• Composed of ferro-magnesium silicates
rich in iron and magnesium
 Molten rock moves in a convection
motion
 The motion causes the movement of
Earth’s tectonic plates.
Outer Core
•
•
•
•

Just below the mantle
2, 266 km thick at outer boundary
Temperature of 4, 400 C
Composed of nickel-iron alloy
Consists of liquid magma- the
solid inner core rotates inside
outer core generating magnetic
field.
 Magnetic field protects Earth from
harmful radiation and solar wind
Inner Core
• Just below the outer core (center
most layer)
• Radius of 1, 220 km
• Temperature of 6, 400 C
• Composed of a solid ball of iron
metal
 Scientists think the inner core
rotates at a different speed