find the center act 1
TRANSCRIPT
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)