Earthquakes!!!!!!!!! http://www.youtube.com/watch?v=4Y-62Ti5_6s&safety_mode=true&persist_safety_mode=1

Have you ever felt the Earth move under your feet? Many people have!! Every day, somewhere on this planet, an earthquake is happening

What is an earthquake? An earthquake is the shaking of the ground caused by rock shifting along a fault. http://www.youtube.com/watch?v=VSgB1IWr6O4&safety_mode=true&persist_safety_mode=1

Locations Most earthquakes occur near the edges of tectonic plates. Tectonic plates move in different directions and at different speeds As a result of these movements, faults occur.

Locations Earthquakes occur along faults because of sliding. Ring of Fire! Redo to include that earthquakes occur at all types of boundaries, but most frequently transform

Locations --- Epicenter The epicenter is the point on the Earth’s surface directly above the earthquake’s starting point. The focus is the point inside the Earth where the quake begins

What causes Earthquakes? Increased stress along faults near the edges of plates This cause the collision, division, sliding of the plates As a result, the rock in the plates deform.

Causes --- Rocks along fault lines deform in two main ways Plastic Deformation Elastic Deformation Rock moves like modeling clay. Will take new shapes Does not break Does not lead to earthquakes While rock can stretch further than steel, it does have a breaking point When the rock breaks, it releases a tremendous amount of energy When the rock breaks, the broken pieces return to their un-stretched shape. This sudden return of elastically deformed rock to its original shape is called elastic rebound. Causes --- Rocks along fault lines deform in two main ways

Causes ---Elastic Rebound During elastic rebound, energy is released. Some of this energy travels as seismic waves. The seismic waves cause earthquakes!

How do waves travel? Waves that travel through the Earth are called seismic waves. Seismic waves that travel through the Earth’s interior are called body waves. There are two types of body waves: P-Waves, and S-Waves

Two types of waves --- P-Waves “P”ressure waves “P”rimary waves Travel through solids, liquids and gasses Fastest seismic waves Travel ahead of other seismic waves Move back and forth, which squeezes and stretches rock,

Two types of waves --- S-waves “S”urface waves, “S” hear waves When rock is deformed from side to side, and after it is deformed, it springs back to its original position and S waves result. Travel through solids Most destructive!!!!

How are Earthquakes Measured? How do seismologists know when and where earthquakes begin? How do seismologists know how strong an earthquake was? Can seismologist predict where and when a future earthquake may take place?

Locating Earthquakes Seismologists use instruments called seismographs to measure earthquakes Seismographs are located at or near the Earth’s surface and record seismic waves. When seismic waves reach a seismograph, a seismogram is created A seismogram is a tracing of an earthquake in motion.

Time and Location of earthquakes Seismologists use seismograms to figure out when earthquakes begin. They also use seismograms to find out an earthquake’s epicenter.

Measuring an earthquake’s strength Seismograms can also find out an earthquake’s strength! There are two scales for determining an earthquake’s power Richter Scale Modified Mercalli scale

Richter scale A scale for measuring power from 1-10 Developed by Charles Richter in 1935 (modified in 1977) Measures the ground motion of the earthquakes

Modified Mercalli scale A scale from I-XII(1-12)is used to measure the damage and effect an earthquake has on the people.