Transcript Evidence of Earths Layers Density and P and S Wavesx

Earth’s Layering
Bell work
• A rock has a MASS of 13.4 grams
• The VOLUME of the rock is 3.6 cm3
• What is the DENSITY of the rock?
• Rank the items from more - less density:
– Glass, wood, iron, plastic
Vocabulary
• Mass: the quantity of matter in a body
regardless of its volume or of any forces
acting on it
• Volume: the quantity of three-dimensional
space enclosed by a closed surface
• Density: the mass per unit volume
= mass/volume
Nebular Hypothesis: formation of the solar system
Earth
Essential Question:
What materials are INSIDE the Earth?
Investigate the Densities of some of Earth’s Rocks.
Rock sample
Mass
(.01g)
Granite
Basalt
Peridotite,
pyroxene, or
olivine
Iron meteorite,
Magnetite or iron
Volume(before)
(0.1 ml)
Volume(after)
(0.1 ml)
VOLUME
Density;
Difference in water
level (ml)
mass/volume
(g/cm3)
Earth’s Rocks Lab tips
• Measure the mass of the rock in grams. Make sure your
balance is on grams (g) and zero
• Fill the graduated cylinder up to 60 ml of water. This is
the volume before (write in your chart).
• Slowly slide the rock down the side of the graduated
cylinder. Record the After volume. If needed, dry well
before repeat.
• Subtract After-before volume to get Final Volume.
• Density of Rock = mass/Final volume
• Bring your data to the front to get class average
Earth’s Layered Structure;
As Earth cooled, the materials: rock and metal were
“sorted” by density
________________g/cm3
name _________________
________________g/cm3
name ________________
____________g/cm3
name ___________
________________g/cm3
name _____________
Earth’s inner and outer core contain IRON and NICKEL density 7.8 – 8.9
How do scientists know that the
Earth has different layers?
How did they discover this?
We know from volcanic activity that there is a layer of molten (melted) magma
rock under Earth’s solid surface.
http://www.discovery.com/tvshows/curiosity/topics/inside-amagma-chamber.htm
Exploring magma
Density of Earth’s (surface) Crustal Rocks
Granite
Basalt
Peridotite, Olivine
Average thickness of Earth’s crust: _______ km
Earth’s radius: 6400 km
What percent of Earth is the crust? _______ %
How is a stud finder able to see
studs behind the wall?
How do bats ‘see’ their prey in
the dark?
How do scientists “SEE” what
is inside the Earth?
• Andrija Mohorovicic
– 1909
– Used seismic waves from
earthquakes
– Noticed a CHANGE IN
VELOCITY of waves
about 50 km depth
– Found a boundary between
the rocky crust and the
magma mantle
– He discovered the Earth
had layers!
Seismic Waves
• Two types of seismic wave behave differently
– depending on the material that they go through
• Compressional primary or P waves
– travel and refract through both fluid and solid materials.
• Shearing secondary or S waves
– cannot travel through fluids like air or water
– Fluids cannot support the side-to-side particle motion
– Travel through solids only
http://www.classzone.com/books/earth_science/terc/content/investigations/es0402/es0402page03.cfm?chapter_no=in
vestigation
Bellringer Question:
Earth
What do P and S waves tell us about the
materials that are INSIDE the Earth?
P-waves travel through SOLIDS and LIQUIDS
S-waves travel through SOLIDS ONLY
stop
Bent
Bounce off
http://www.classzone.com/books/earth_science/terc/content/investigations/es0402/es0402p
age05.cfm?chapter_no=investigation
Shadow Zone:
A zone where no
waves pass
through Earth.
P-waves reappear
later, but bent at
a different
location.
S-waves don’t go
through at all!
There must be a
liquid layer below
the mantle:
A liquid CORE!
Draw and Label the parts of the Earth on this Diagram!
P waves are bent as they
pass through the outer core
Some P waves actually
bounced off!
They must have hit a
SOLID INNER CORE
(Discovered in 1936)!
A liquid outer core!
• molten / melted (liquid)
(S-waves don’t pass through)
• If it is a liquid it must MOVES / FLOWS like a liquid
But liquid what? What material makes up the
outer core?
How hot is it at the core?
What is the Earth’s core made of?
Let’s look at more Evidence and do the
math…
Density of Earth’s CRUST:
2.6
Granite __________
g/cc
3.1
Basalt ___________
g/cc
3.3
Peridotite _________
g/cc
Average: _________ g/cc
Density of crust and mantle
Earth’s Average Density:
5.5 g/cc
Density of iron: 7.8 g/cc
Density of Nickel 8.9 g/cc
• The outer core is IRON
– IRON and NICKEL (alloy)
• Liquid, molten magnetic
IRON
• Flowing magnetic iron gives
Earth’s its magnetic field
Velocity of P and S waves change with depth
– they move ________. Now do the
Temperature graph!
Density of Earth’s Material vs. Depth
(density is one measure of the PRESSURES exerted by Earth’s layers)
On your POM chart write down what
this tells you!
Bellringer: Name and describe the four parts
of the Earth.
Is the temperature
inside the Earth
hot enough to melt
iron and nickel?
Earth’s internal
TEMPERATURES
change as depth
increases. They
__________
This indicates a
change in the type
of material.
Different Layers!
Earth’s Internal Heat Source
1. For millions of years Earth was bombarded by high velocity
meteorites and comets
These collisions generated immense amounts of HEAT energy
and melted the metals and rock on the young planet.
2. Decaying radioactive rocks in Earth release heat energy.
3. Immense Pressure from the weight of Earth’s layers heat Earth
So….Earth’s 4 layers were determined by
physical properties….
1. Temperatures and pressures
(both increase and change with greater depth)
2. Physical properties
(density, chemicals and elements)
3. Mechanical behavior
(how the material moves or doesn’t move: solid or liquid)
ACT Science Test Prep Question
1. Figure 1 shows that a seismograph
located at 125° around the Earth
from the earthquake focus would
receive which type(s) of seismic
waves?
A. P-waves only
B. S-waves only
C. Both P and S waves
D. Neither P or S waves
2. According to Figure 1, when P-waves
encounter the boundary between the
mantle and the core, the P-waves most
likely:
F. Stop and do not pass into the core
G. Enter the core and are refracted
H. Change into S-waves
J. Change to a third type of wave