Find The Center

Plate Tectonics

Compare and Contrast:

1. Continental Crust and Oceanic Crust

2. Lithospheric Plate and Plate Tectonic

3. Primary Waves and Secondary waves

4. Epicenter and Focus5. Seismogram and Seismograph

Recall: Seatwork

Continental and Oceanic

Crust

Crust is not the same all over the earth.

- under continents or large islands- is about 35 -60 km thick- rich in potassium, sodium, aluminum,

silicon

Continental Crust

- beneath the oceans- thinner – 7 to 10 km- under the oceans of the world- covers about 70.8% of the surface of the

earth- rich in iron, sodium and magnesium- denser than continental

Oceanic Crust

Lithospheric Plate and Plate

Tectonics

Outer part of Earth, including both crust

and the uppermost mantle - consists mostly of the cold, strong uppermost

mantle

Lithospheric Plate

Outermost rigid layer of the earth is broken in

several segments called plates and these are in motion.

Australian-India Plate North American Plate South American Plate African Plate Pacific Plate Eurasian Plate Antarctic Plate

Plate Tectonic

P-waves and S-waves

Primary waves

- Compressional wave- Push rocks in the direction they are

traveling - Faster and can travel through all

states of matter

P-waves

Secondary Waves / Shear waves

- displacing rocks at right angles to their direction of travel

- cannot pass through liquids

S-waves

Epicenter and Focus

- the point on the earth’s surface which is directly above the focus

- most violent shaking occurs here

Epicenter

Seismogram and

Seismograph

Plate Tectonics

Crust

Continental and Oceanic Upper Mantle

(Asthenosphere)

Lithosphere

in constant but slow motion ARCTIC RIDGE: slowest (less than

2.5cm/yr) EAST PACIFIC RISE near Easter

Island, in the South Pacific about 3,400 km west of Chile : fastest(more than 15cm/yr)

The movement is called TECTONICS

Lithosphere

What are the basis of scientists in dividing the lithosphere in this

manner?

PROCEDURE: Refer to the activity sheets. Write all your answers in a 1 whole sheet of

paper. Complete the table. Copy and Answer Q1 to Q4. Draw the map with the three circles

intersecting or nearly intersecting at a point. The intersection is the EPICENTER.

Act. 1: Find the center.

Table: 560 km; 400 km;

480km Q1. ...epicenter Q2. ...difficulty if only 2

stations Q3. ...distance of epicenter Q4. ...importance of

determining epicenter

Q and A

Locating the

Epicenter Step 1: Determine the difference in arrival

time for your P-wave and your S-wave

Locating the

Epicenter

Locating the

Epicenter

Locating the

Epicenter

a method that involves taking seismographic measurements from at least three separate seismic stations. Seismologists measure the time it takes seismic waves to reach the recording stations, as well as the magnitude of the waves, and triangulate the measurements to calculate the location of the epicenter.

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Triangulation

Locating Epicenter: Triangulation

Locating Epicenter:

Triangulation

Philippine Monitoring Stations

Seismologists

P waves travel faster than S wave Because of this difference in velocity

the distance of the epicenter from the recording station can be determined.

Triangulation method is used to determine the exact location of the epicenter.

Remember:

Determining the location

of earthquake epicenters plays a vital role in laying the foundations of plate tectonics.

Remember:

How do you think early

geologists used the plotted positions of earthquake epicenters throughout the world in conceptualizing crustal movements?

But....

Printed copy of

Map of earthquake distribution Map of active volcanoes of the world Map of the Mountain ranges of the world

2 Plastic sheets/cover, same size as your printed map

Marking pens (2 different colors)

Bring: (by group)