1. Earthquakes 4 th Quarter Science April 22-26

2. What causes an earthquake? “Earthquakes” video 1:29 Earthquakes happen for 2 important reasons. First, Earth is like a ball with many layers. It has an outer later called the crust. That’s the surface of the Earth, where people, plants, and animals live. Under the crust is another layer called the mantle. The mantle is partly made up of liquid rock. Earth’s crust floats on the mantle. The core is divided in two layers, the inner core and the outer core.

3. Causes of Earthquakes The second reason for earthquakes is that Earth’s crust isn’t just one piece. It is made up of many pieces, like a puzzle. The pieces are called tectonic plates. The plates float on the molten rock of the mantle, so they are always moving. Where the edges of the plates meet, they cab rub against each other. Sometimes they get stuck, and when that happens, tension builds up. When they finally get ‘unstuck’, they can cause the ground to move and shake. Text book pages C10-C15.

4. How do earthquakes change the surface of the Earth? Earthquakes can happen almost anywhere on Earth. But, they are more common in certain areas. Places where Earth’s plates meet have more earthquakes than places far from the edges do. Also, these areas tend to experience a greater number of large, destructive quakes. “Earthquakes and Mountains” video 4:39 eBook Assignment, “Earthquake Zone”

5. How Are Tsunamis Related to Earthquakes? Earthquakes can happen on the part of the Earth’s surface we call “land”, but the can also happen on the ocean floor. The tectonic plates are not the same as continents. Remember that the ocean floor is part of the Earth’s crust. It is just a part that is covered with water. When an earthquake happens on the ocean floor, it can cause a large wave called a tsunami. Tidal Wave video 12:00 Reading passage, “Sizing up the Seismos”