CHAPTER 10, SECTION 2Standards 3d. Students know why and how earthquakes occur and the scales used to measure their intensity and magnitude.

Objective 1

Describe elastic rebound.

Objective 2

Compare body waves and surface waves.

Objective 3

Explain how the structure of Earth’s interior affects seismic waves.

Objective 4

Explain why earthquakes generally occur at plate boundaries.

Assessment

Flap Book, Daily Quiz, Chapter Test

Review Daily Bellwork, Science Starters, Standards Practice

Chapter 12, Section 1

KEY TERMSCreate a flashcard for each of the following terms (found on p.295 in your text book). Earthquake Elastic rebound Focus Epicenter Body wave Surface wave

P wave S wave Shadow zone Fault zone

If you finish early, study your flashcards!

INTERACTIVEQuickwrite:

Describe what happens when a rock is thrown into a pond. How might this be similar to an earthquake?

WHY EARTHQUAKES HAPPEN Earthquakes are movements of the

ground caused by a sudden release of energy when rocks along a fault move.

Rocks on both sides of a fault are pushed tight against each other. As stress builds up on one or both sides the rocks eventually and suddenly slip past each other. This causes the shaking of an earthquake.

ELASTIC REBOUND Elastic Rebound is the sudden return of

elastically deformed rock to its undeformed shape.

ELASTIC REBOUND DEMO

ANATOMY OF AN EARTHQUAKE The FOCUS = the location along a fault

where the earthquake occurs. EPICENTER= the point on the Earth’s

surface directly above the focus.

INTERACTIVE! Draw and label a diagram for an

earthquake…

QUICK CHECK!!1. What is the difference between the

focus and the epicenter? ________________________________________________________________________

2. __________ ________ is the theory that rock returns to its original shape.

SEISMIC WAVES As rocks slip along the fault lines the

energy released as vibrations are called SEISMIC WAVES.

Waves are like the ripples in a pond when you throw a rock in.

2 types of waves: Body Waves Surface Waves

BODY WAVESP Waves• Primary or Compression Waves• Fastest, first waves to be detected• Rock moves in a Back and Forth direction

parallel to the direction the waves are travelling in

• Move through solids, liquids, and gasesS Waves• Secondary or shear waves• Slower than P waves• Rock moves side to side perpendicular to the

direction in which the waves are traveling

ENJOY THE MUSIC AND THE SHOW Seismic Waves

Brainpop--Earthquakes

WHERE DO EARTHQUAKES OCCUR? Earthquakes generally occur near tectonic plate boundaries. Convergent Oceanic Environments

Divergent Oceanic Environments

Continental Environments

FAULT ZONES Fault zones are at plate boundaries Regions of numerous, closely spaced

faults Faults are breaks in a body of rock (like

a giant crack)

Let’s Go Online…

EARTHQUAKES AWAY FROM PLATE BOUNDARIESEarthquakes in places such as Missouri and Arkansas,occur because of ancient fault zones deep within the Earth’s crust.

ASSESSMENT Choose 6 of the 11 questions on page 300 to answer.