Topic 12: Dynamic Earth

Using Your Marble

List the names of the interior layers of the Earth beginning with the core.

But wait, we didn’t learn that…… where ever could we find such information?

Interior Layers of the Earth: Using the copy of page

10 in the ESRT, count how many interior layers there are inside Earth and take a colored pencil for each layer.

Color each layer a different color.

With you partner, answer the questions about the layers.

How is it possible for us to know all of this about the inside of Earth?

Interior Layers of the Earth:

Interior Layers of the Earth:

Earthquakes An earthquake is the

vibration of Earth produced by rapid release of energy.

Focus is the point within Earth where the earthquake starts.

Epicenter is the location at the surface directly above the focus.

Earthquakes Faults are fractures in Earth where

movement has occurred.

Earthquakes

Earthquakes are caused when the strength of the rock is exceeded.

It suddenly

breaks causing the vibrations of an earthquake.

Earthquakes• These vibrations travel in the form of

seismic waves.

There are two kinds of seismic waves

Body waves travel through the Earth.

When body waves reach the surface of the Earth they are called surface waves.

Earthquakes

There are two types of body waves travel through Earth:

1. P waves

2. S waves

P waves (compression) can travel at the fastest speed and can move through solid, liquid, and gas!

S waves (shear) travel slower and can only move through solids!

Earthquakes

Which interior layers of Earth can S waves move through? (Use your ESRT)

Why?

Earthquakes

What causes a Tsunami?

A Tsunami is an underwater earthquake. When there is a shift in the ground

underwater, it displaces or moves the water. The water waves travel trough the deep water. When they approach shallow depths, the

energy in the wave is conserved by increasing wave height.

What causes a Tsunami?

Let’s meet Patty and Sarah!

Earthquakes

A seismograph is an instrument used to detect and record seismic waves.

A seismogram is the actual recording on paper.

Earthquakes

How do we know that P waves (compression) travel faster than S waves (shear)?

Earthquakes

-How do we know that P waves (compression) travel faster than S waves (shear)?

Earthquakes

-How do we know that P waves (compression) travel faster than S waves (shear)?

-Because they always show up first on a seismogram.

Earthquakes (ESRT p.11 Practice)

According to the graph of Earthquake P-wave and S-wave Travel Time in the reference information, what is the approximate total distance traveled by an earthquake’s P-wave in its first 9 minutes?

2,600 km 5,600 km 7,600 km 12,100 km

Let’s have some fun with numbers!!!

Earthquakes

What can the difference in P wave and S wave travel time can tell us about an earthquake?

Let’s figure it out together……..

Turn to page 11 in your ESRT!

Earthquakes

EarthquakesSeismograms at three stations

Earthquakes

*Which Station is closer to the earthquakes epicenter? *What information did you use to figure that out?

Station A: San Francisco, California

P-Wave arrival 3:02:20 S-Wave arrival 3:06:30

What is the time difference between P and S wave arrivals?

Station B: Denver, Colorado

P-Wave arrival 3:01:40 S-Wave arrival 3:05:00

What is the time difference between P and S wave arrivals?

Station C: Missoula, Montana

P-Wave arrival 3:01:00 S-Wave arrival 3:03:00

What is the time difference between P and S wave arrivals?

San Francisco: 4:10Denver, Colorado: 3:20Missoula, Montana: 2:00

Earthquakes

Time to….Surf the wave!

TAKE A PIECE OF PAPER, AND MARK OFF THE DIFFERENCE IN ARRIVAL TIME

MOVE THE PAPER UNTIL THE TWO TICK MARKS LINE UP WITH THE P AND S CURVES

WHEN TICK MARKS LINE UP, GO STRAIGHT DOWN AND READ THE EPICENTER DISTANCE

EPICENTER DISTANCE OF 2800 KM

San Francisco: 4:10

Denver, Colorado: 3:20Missoula, Montana: 2:00

Try the other two on your own.

San Francisco: 4:10 2,800km

Denver, Colorado: 3:20 2,000kmMissoula, Montana: 2:00 1,100km

The diagram shows data received at a seismic station following an earthquake.

The distance from this seismic station to the epicenter of the earthquake is approximately…..

a. 1,300 km b. 2,600 km c. 3,400 km d. 5,000 km

Earthquakes (ESRT p.11)

Let’s practice with Epicenter Info!

Earthquakes

Earthquakes So what does this distance we get from

the ESRT tell us anyway?

San Francisco: 4:10=2,800km

1,00

0

2,00

0

3,00

0

4,00

0

5,00

0

Open your compass to the EXACT distance on the scale.

. .

.

2,800km

San Francisco: 4:10 2,800km

Denver, Colorado: 3:20 2,000kmMissoula, Montana: 2:00 1,100km

. .

.

2,800km 2,000km

San Francisco: 4:10 2,800km

Denver, Colorado: 3:20 2,000kmMissoula, Montana: 2:00 1,100km

. .

.

2,800km 2,000km

1,100km

. .

.

2,800km 2,000km

1,100km

Earthquakes

We know that P and S waves are the body waves that travel through Earth.

Surface waves only travel along Earth’s surface.

We describe surface waves as either Love waves or Raleigh waves.

Check this out

Earthquakes

geo.mtu.edu/UPSeis/waves.html

But wait, how do P and S waves behave? Time to play with the slinky!!! How can we get the slinky to behave like a

P wave? An S wave? Recall the terms compressional and

shear.

Earthquakes

• Team Challenge: Each class will be timed!!

• Make a human P wave in order to get “energy” to travel from one side of the room to the other!

• Then make a human S wave!!!

• Ready….Set…..Go

Earthquakes

Recall: When traveling through the same material P waves move faster than S waves.

Recall: S waves can only travel through solids while P waves travel through solids and liquids!

Earthquakes

-Waves refract (change direction) and speed up as density increases.-Since density increases with depth, the wave path looks something like this…….

Earthquakes

Shadow Zone (120 degrees, 143 degrees)

Richter Scale Mercalli Scale