Plate Tectonics Lesson 4

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# Plate Tectonics Lesson 4 - PowerPoint PPT Presentation

Plate Tectonics Lesson 4. Big Idea: How Do Earthquake’s Affect Earth’s Surface?. Earthquakes?. If you were holding a ruler at both ends and put pressure on both ends at the same time, the ruler will bend slightly. If you press very hard, the ruler will snap in two.

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### Plate TectonicsLesson 4

Big Idea:

How Do Earthquake’s Affect Earth’s Surface?

Earthquakes?

If you were holding a ruler at both ends and put pressure on both ends at the same time, the ruler will bend slightly. If you press very hard, the ruler will snap in two

An EARTHQUAKE is a release of energy at a fault that causes Earth’s crust to shake.

The focus is the point inside Earth where the crust slips and releases energy.

The epicenter is the point on the Earth’s surface directly above the focus.

There are three types of earthquake waves:

P waves are primary waves and they move with the greatest speed.

S waves are secondary waves and can move up and down or side to side. Their movement looks somewhat like the letter S.

Surface waves travel along the Earth’s surface. They can most of the damage to buildings in an earthquake.

Measuring EarthquakesScientists study the intensity (how much shaking there is) of an earthquake with different instruments and scales.
• In the early 1900’s Giuseppe Mercalli developed a scale that let people calculate the intensity of an earthquake.
In 1935, Charles Richter developed an earthquake scale based on the heights of waves recorded on a seismograph.

An earthquakes’ magnitude is the amount of energy it releases.

The Richter Scale
the distance of a place from the epicenter

Earthquake damage 100 km from the epicenter

the epicenterEarthquake damages 200 kilometers from the epicenter:

Local geology

Countries such as Japan that are surrounded by water have greater damage

Softer ground shakes more than harder ground