Nature’s Forces

What does this sound like? Has anyone ever experienced an earthquake? Why do you think an earthquake makes those sounds?

Objectives Understand how an earthquake happens Plan the best and safest way to survive an earthquake Create own mini earthquake to see how shock waves can be so damaging

Question If you find yourself indoors during an earthquake, is it better to rush outside or to take cover inside?

It’s better to Stay Inside!! Many people are injured by falling debris just outside buildings. Usually it's better to stay inside, if you are already inside, and to stay outside if you are already outside. Inside, try taking cover underneath something sturdy like a desk, and avoid windows, mirrors, and heavy furniture that might fall such as overloaded bookshelves. Outside, avoid walls, chimneys, and electrical power lines. Try not to look up, however: because it's important to protect your head!!

How do earthquakes happen? Earthquakes are usually caused when rock underground suddenly breaks along a fault. This sudden release of energy causes the seismic waves that make the ground shake. When two blocks of rock or two plates are rubbing against each other, they stick a little. They don't just slide smoothly; the rocks catch on each other. The rocks are still pushing against each other, but not moving.

After a while, the rocks break because of all the pressure that's built up. When the rocks break, the earthquake occurs. During the earthquake and afterward, the plates or blocks of rock start moving, and they continue to move until they get stuck again. The spot underground where the rock breaks is called the focus of the earthquake. The place right above the focus (on top of the ground) is called the epicenter of the earthquake.

Different Types Of Earthquakes There are many different types of earthquakes: tectonic, volcanic, and explosion. The type of earthquake depends on the region where it occurs and the geological make-up of that region. Tectonic earthquakes are the most common. These occur when rocks in the earth's crust break due to geological forces created by movement of tectonic plates. Volcanic earthquakes occur in conjunction with volcanic activity. Collapse earthquakes are small earthquakes in underground caverns and mines. Explosion earthquakes result from the explosion of nuclear and chemical devices. We can measure motion from large tectonic earthquakes using GPS because rocks on either side of a fault are offset during this type of earthquake.

The most recent earthquake happened… In New York City on. Saturday, October 27 th. What Happened? It was very minor, and people were just slightly shaken up, but there was no damage done to the city. What might people have mistaken it for? Terrorist attacks………This is why we need to prepare….

How to prepare for an earthquake: Prepare an emergency plan for your family and household. Take a first aid course, including cardio- pulmonary resuscitation (CPR). Know the safe places to be - and where not to be - in your home during an earthquake. Practice taking cover in the safe places. Safe places under heavy tables or desks; inside hallways; corners of rooms or strong archways.

Dangerous places : near windows or mirrors; under any heavy objects that can fall; the kitchen where the stove, refrigerator or contents of cupboards may fall on you; doorways where the shaking may slam the door on you. Chances of survival are improved if emergency plans are prepared and practiced together with your family. Start by discussing what could happen and what you should do at home, at school or at work if an earthquake strikes. Prepare a list of what needs to be done ahead of time. Divide up tasks so that everyone involved in the plan participates as much as possible. Write down and exercise your plan. Make sure everybody has a copy and keeps it close at hand.

Hands-On Activity Earthquake and Shock Waves Materials: Plastic Table Three cups of sand Rubber Mallet.

Procedure: 1. Pour three cups of sand on the top of a plastic table near the edge. 2. Tap the table lightly with the rubber mallet. You will see the sand "jump" into the air. As rocks snap and break at the focus of an earthquake shock waves are sent out in all directions. The "jumping sand" represents the release of the energy from the hammer through the plastic table.

3. Move the sand farther away from the point of contact and see what happens. The farther away the sand is from the source of energy (tapping of rubber mallet) the less the sand jumps. This represents the fact that the farther you are from the epicenter the less you will feel the earthquakes shock waves.. 4. Move the sand to the opposite side of the table and tap lightly. You should observe a very small movement of the sand.

Closure When you go home today, talk with your family about how to prepare for an earthquake, and share with them what you have learned.