Earthquakes What is an Earthquake? An earthquake is the sudden and sometimes violent shaking of the Earth’s crust. It can have devastating effects on the land and areas on the surface as a result of the shock waves from the energy built up underground. How Can You Move Your Plates? Use two pieces of paper. Can you remember the different ways can you move the plates around? Rubbing together Towards each other Away from each other This kind of movement causes earthquakes. An earthquake happens as a result of energy being released in the form of seismic waves after a build up at a plate boundary. Plate movement Pressure builds up between plates Watch this video https://youtu.be/dJpIU1rSOFY Large earthquakes often occur at tectonic plate boundaries. Small earthquakes happen on these boundaries several times a day, but are so small that they can only be detected with specialised equipment. The tectonic plates which make up the Earth’s crust are constantly moving. This movement is so slow that it cannot be felt by those living on Earth. When two plates slide past each other it is called a conservative plate boundary. As the plates push past each other, they can get stuck. This causes pressure to increase until the plates deform and suddenly jolt past each other. Energy that has built up under the ground during this time is released as seismic waves and causes the damage we see from earthquakes. Where do Earthquakes Occur? Earthquakes happen frequently in these areas. What do you notice about where they happen? Make your own earthquake This simple earthquake experiment lets us know why buildings in earthquake-prone areas need to be built differently to withstand the fallout of the quakes. Activity time Supplies needed: ■ metal cookie sheet / any sheet ■ wooden blocks ■ Lego bricks Directions: 1. 2. First, have the students construct a tower on the cookie sheet using the wooden blocks. Have two of the kids sit on either side of the cookie sheet and shake it as if there were an earthquake. Not surprisingly, when we did this, the tower crumbled with very little shaking and the blocks fell. The metal cookie tray is meant to represent a tectonic plate and the shaking represents the shifting that happens with an earthquake. Directions Part Two: 1. 2. 3. Next, work together to construct a tower with interlocking Lego blocks. Our kids, are always excited when Lego and school collide! Made it approximately the same height and shape as the wooden block tower. For us, it took much longer of course to make the Lego brick tower, which led to a discussion about how sometimes doing things the right way takes more time. Set the new tower on the cookie sheet and have two kids sit on either side (in order for the experiment to be as scientific as possible, we wanted to use the same people so that they could attempt to create the same earthquake force). At first, they recreated the same shaking they had the first time and the tower stayed intact. Simulate a larger, more powerful earthquake. When we did this, they became more and more forceful with the shaking, eventually lifting the tray up and banging it up and down as well as side to side before they were able to knock the tower over and dislodge a few of the bricks. How Strong Is It? There are two main ways to measure the power of an earthquake. Machines called seismographs measure the power of an earthquake at its epicentre on a scale called the Richter scale. Another measure is the Mercalli scale, and this is based on people’s observations during an earthquake. Comparing Earthquakes Mercalli Intensity Intensidad de Mercalli Effect I Felt by no-one. II Felt by very few people. Hanging objects may swing. III Felt by many but they don’t realise it is an earthquake. IV Felt indoors by most people. Vibrations similar to a lorry hitting a building. V Felt by nearly everyone. Sleeping people may be woken. Trees and poles sway. VI Felt by all. People run outside. Furniture moves. Slight damage to property. Comparing Earthquakes Mercalli Intensity Intensidad de Mercalli Effect VII Felt by all. People run outside. Moderate damage to buildings VIII Specially designed buildings damaged, others collapse. IX All buildings damaged. Cracks appear in ground. X Many buildings destroyed. XI Almost all buildings destroyed. Wide cracks in the ground. Water, gas and electric out of action. XII Total destruction. The ground moves in waves or ripples. Preparing for an Earthquake Drop, Cover and Hold Duck under a strong table or desk. Cover your head and neck with your arms. Stay away from windows. Stay Calm Make safe choices for yourself and those around you. Stay Shelter in place. Whether you’re in a car, in bed, or in a public place. Do not try to run out of the building during strong shaking, hold tight until the shaking stops. Tsunami What Is a Tsunami? What do you think a tsunami is? Tsunami is a Japanese word. It means ‘Harbour Wave’. A tsunami is a giant wave. Was your idea close to the real meaning? What Causes a Tsunami? A tsunami is a giant wave caused by a huge earthquake under the ocean. The earthquake causes a large amount of water to be displaced very quickly. A series of waves travel through the deep water. As the waves travel through shallow water near the land, they get bigger. Did you know? Before the tall wave hits the land, the water level at the shore will drop. What Damage Does a Tsunami Cause? What can you see that looks out of place? What kinds of damage have occurred in the area? If you were in a rescue team who have just arrived at the scene, what kinds of help might you need to give? Why are Tsunamis Dangerous? They are very fast and powerful. You cannot out-run a tsunami. Once the tsunami hits land it keeps going. The waves are strong and can damage, sometimes destroy buildings, vehicles and other items on land. The waves continue to travel fast as they move across the land. There may be more than one wave. They can travel far. The wave may carry debris. One large wave can hit hours after the first rolls onto land. As waves move across the land, they collect and pick up things in their path. Tsunami Warnings Natural Warnings If you live in a coastal area, you will be aware of your environment and its changes. Some things to look out for are: • a strong or long earthquake; • a sudden rise in sea level; • unusual noises from sea (can often sound like a train or a jet). Tsunamis Around the World Japan – 2011 At 2:46pm, an 8.9 magnitude earthquake struck the north-east coast of Japan. The quake triggered a huge tsunami which swept inland. In places, the tsunami waves reached as far as 10km inland and entire towns virtually disappeared. Japan has the longest recorded history of tsunamis. Sumatra, Indonesia – 2004 This Indian Ocean earthquake and tsunami was the most devastating of its kind in modern times, killing 230,000 people in 14 countries, and caused 30m high waves. It was the third largest earthquake ever recorded, had the longest duration ever observed (8.3 - 10 minutes), and caused the entire planet to vibrate. Tsunamis Around the World Italy - 1783 Lisbon – 1755 The earthquake and tsunami almost totally destroyed Lisbon 100,000 people. Italy – 1908 The Messina earthquake and tsunami took about 123,000 lives in Sicily and Calabria, southern Italy. The major cities of Messina and Reggio Calabria were almost completely destroyed. The Calabrian earthquakes were a sequence of five strong earthquakes that hit the region of Calabria, producing two tsunamis. Between 32,000 and 50,000 died during this earthquake. Watch this video https://www.nationalgeographic.com/environment/article/tsunamis Thank you
