Presentation on theme: "By Bethany Brewer. What is an earthquake? Earthquakes are the sudden shock of the earth’s surface. They are the Earth's natural means of releasing stress."— Presentation transcript:
What is an earthquake? Earthquakes are the sudden shock of the earth’s surface. They are the Earth's natural means of releasing stress. More than a million earthquakes rattle the world each year. The countries that are most at risk of having an earthquake are unknown precisely, as earthquakes can happen in many continents and countries around the world. Earthquakes can be felt over large areas although they usually last less than one minute.
What causes earthquakes? There are about 20 plates along the surface of the earth that move slowly past each other. When the rocks shift with great force, it causes an earthquake. As the Earth’s tectonic plates move they put forces on themselves and each other. When the force is large enough, the crust is obligated to break. When the break occurs, the stress is released as energy which moves through the Earth in the form of waves, which we feel and call an earthquake.
Where do earthquakes happen? Within areas of the crust are fractures, known as faults, along which two crustal blocks have slipped or moved against each other. One block may move up while the other moves down, or one may move horizontally in one direction and the other in the opposite direction. Earthquakes occur repeatedly at faults, which are zones of weakness in the earth's crust.
Why does the earth shake during an earthquake? Earthquakes occur at the boundaries of tectonic plates where stresses accumulate in the Earth's crust, causing energy to be stored in the form of elastic strain (like the elastic strain in a spring). Ultimately this stress will ascend the strength of the crust in the fault causing a sudden brittle failure or rupture. This causes movement and a sudden release of the stored elastic strain energy in the form of waves (as well as heat) causing an earthquake. These waves cause the ground motions or shaking.
What are ‘after shocks’? Aftershocks are “mini” earthquakes that follow the largest shock of an earthquake sequence. They are smaller than the main shock and within 1-2 rupture lengths distance from the main shock. Aftershocks can continue over a period of weeks, months, or years. In general, the larger the main shock, the larger and more numerous the aftershocks, and the longer they will continue.
How is a ‘Tsunami’ related to an earthquake? When earthquakes happen underwater, they cause the ground level to rise and therefore cause water to flow largely in one direction. This makes an extremely large and deadly tidal wave which then crashes into and destructs whatever is in it’s path. On 26 th December, 2004, a deadly and tragic tsunami hit many islands in the Pacific Ocean killing at least 275,950 people including children.
How do scientists measure earthquakes? There are two ways which scientists use to measure earthquakes. They measure the severity of the earthquake, using the Richter scale and they measure the damage caused by the earthquake, using the Mercalli scale. The Richter scale works by taking readings of vibrations caused by earthquakes. The vibrations are calculated through a mathematical device which then is measured from 0 to 10+. The Mercalli scale measures the strength of an earthquake kind of like the Richter Scale but this scale uses the observations of the people who witnessed the earthquake to estimate its intensity on a scale from1 to 12.
Can scientists predict earthquakes? Earthquakes cannot be predicted - although scientists are working on it! Scientists were convicted in Italy for failing to predict a deadly earthquake. But no one can predict when an earthquake will happen, or how big it will be. There are increased amounts of data, new theories and powerful computer programs and scientists are using those to explore ways that earthquakes might be predicted in the future. We can certainly hope that someday we’ll be in a world where an earthquake can be predicted before it occurs and give us time to move away from it to reduce deaths.
What environmental impact do earthquakes have? Earthquakes have many environmental impacts on our earth including the deaths of people and sometimes, animals. Also many natural things are affected largely like landslides, tsunamis, ground failure, seiche and many secondary effects such as broken water pipes, hazardous material spills and electrical and gas pipe leaks.
Bibliography http://www.weatherwizkids.com http://wiki.answers.com http://earthsky.org http://www.ehow.com http://images.google.com.au http://www.animationfactory.com http://answers.askkids.com And my own knowledge!!!! Earthquakes
Thank you Mr Knobel and students!! Please note that these were real life pictures of tragic tsunamis and earthquakes around the world and many people lost their lives.