Download Earth`s Internal Processes

Earth’s Internal Processes
Section 3
Earth’s Interior
Inside the Earth

Scientists learn about the interior by:
◦ Drilling a hole 200 m into the oceanic crust
◦ Studying the behavior of seismic waves
Earth’s interior is not the same
throughout
 Earthquake waves arrive at different times

Earthquake Observations
•
A boundary that marks a density change between layers is called a
discontinuity.
Think – Pair - Share

Why do you think that scientists
attempted to drill through oceanic crust
instead of continental crust?
Earthquake Observations
Seismic recording stations like ours
record seismic wave data.
 Waves refract when they encounter sharp
changes in density.

Shadow Zones
P- and S- waves spread out from an
epicenter
 Waves travel through 105 degrees of arc
 Shadow Zone – “dead zone” between 105
and 140 degrees
 From 140 to 180 degrees only P-waves
are recorded

Earth’s Interior
3
Shadow Zones
Earth’s Core

Shadow zones reveal
◦ A layer in the interior
may be absorbing
waves
◦ S-waves turn into Plike waves
◦ S-waves travel only
through solids
◦ Outer core may be a
liquid
Inner Core
P-waves are refracted as they pass
through the inner core
 Inner core must be denser than outer
core
 Pressure of outer core keeps the inner
core solid
 Outer core remains liquid because of the
high temperatures

Composition of Layers
Layers become denser with depth
 Lithosphere – crust & upper mantle

◦ Rocky materials – mostly silicates

Asthenosphere – weaker layer under
lithosphere
◦ Plasticlike layer

Mantle – divided into upper and lower
◦ Made of silicates
Composition (con’t)

Core – divided into outer and inner
◦ Mostly nickel and iron
Earth may have formed from meteoritelike material
 Material was forced together by gravity
and melted
 Densest materials are in the core, less
dense ones float on the surface

.
Post PowerPoint

What do scientists know about Earth’s
interior?

How do they know this?
Section Check
Question 1
What is Earth’s core made of?
Answer
Earth’s core is primarily made of metallic material such
as iron and nickel.
Section Check
Question 2
Earth’s internal layers become _______ with depth.
A. cooler
B. darker
C. denser
D. lighter
Section Check
Answer
The answer is C.
Section Check
Question 3
Why can’t S-waves penetrate the liquid outer core?
Answer
S-wave only travel through solids. This suggests that the outer
core is in a liquid state.