What is an earthquake? The text describes an earthquake as something that happens “when two blocks of earth suddenly slip past one another.” A fault is where this happens. The hypocenter is where the earthquake begins. The epicenter is the spot above the hypocenter.
Graphic #1 shows layers of the Earth. This diagram shows that the hypocenter of an earthquake is below the surface of the Earth. It also shows that one “block” of earth might shift higher than another “block” of earth.
What causes earthquakes andwhere do they happen? This section explains that there are four layers of the Earth, which include the inner core, the outer core, the mantle, and the crust. The surface of the Earth is not just one large piece—“it is made up of many pieces like a puzzle.” The puzzle pieces are tectonic plates. Sometimes, plates get stuck. When they become “unstuck,” there is an earthquake.
Graphic #2 shows the four layers of the Earth. This diagram helps the reader understand that these layers are not all the same size. It also shows the distance in km of each layer. The lithosphere is the smallest layer. The core, including the inner core and outer core, is larger than the mantle.
Why does the earth shake whenthere is an earthquake? When the edges of two faults are stuck, energy is stored up. When the two faults move, the stored energy comes out in waves. These seismic waves come “outward from the fault in all directions.” The text says these waves are “like ripples on a pond.” Then, these waves are what shake the Earth during an earthquake.
Graphic #3 shows the different plates on the Earth. This map helps the reader understand that some of the plates are larger than continents. Also, some of the plates have more than one continent on them. It also shows that the oceans are on top of the plates.
What I would add: I would add photographs of what it looks like when an earthquake happens. I would even add photos of how earthquakes affect buildings and people’s homes.
Source: “The Science of Earthquakes.” US Geological Survey. 27 Oct. 2009. Web. 22 Mar. 2012.