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Earthquakes and Tsunamis
Quiz by Catie Neumeyer
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Earthquakes and tsunamis: Honshu, Japan, 2011What is an earthquake? Would you be surprised to learn that several million earthquakes happen every year? Seriously. Most are so small in magnitude or size that we cannot even feel them. In fact, only 20 earthquakes are efficiently reported each year in the United States Geological Survey. Wow! That is a huge difference! The Earth has four major layers. Inner core, outer core, mantle, and crust. Think of the crust and top of the mantle like the skin of the earth. This skin is made up of different pieces of rock called tectonic plates. There are about 15 major slabs that join together, kind of like a puzzle. The edges around the tectonic plates are called plate boundaries. These massive pieces of rock slide back and forth under the Earth's surface, bumping up against each other and creating a lot of tension. This tension and movement create faults, which are basically huge cracks in the rock. When the faults get stuck, they build up pressure. And when they get unstuck, you guessed it, an earthquake. So basically, an earthquake is caused by the shifting and sliding of tectonic plates on the Earth's upper mantle and crust. There are three ways that tectonic plates shift or slide. They are subduction, lateral sliding, and spreading. Subduction happens when plates crash into each other. This can cause one plate to slide under another and be destroyed. Or the edges of the plate may rise up and form mountains. Lateral sliding means that the plates slide alongside each other, which can create lots of friction. And like you might have guessed, spreading happens when plates move apart from each other. When they do, melted rock between the plates rises and cools, forming new crust. Here's an interesting fact. Nearly 90% of all earthquakes begin in the Pacific Ocean, in an area called the Ring of Fire. It's called the Ring of Fire because along with earthquakes, it's filled with many active volcanoes. More than 450! Earthquakes can be powerful enough to change the surface of the earth and can do a lot of damage. And sometimes earthquakes can even cause other natural disasters, like avalanches, landslides, and tsunamis. Pretty wild, right? The epicenter is the location of an earthquake on the Earth's surface. The closer you are to the epicenter, the more of the earthquake you will feel. Earthquakes lose intensity as they travel away from the epicenter. Scientists measure the intensity of an earthquake using a special device called a seismograph. Seismometers detect and measure the vibrations given off by an earthquake. Magnitude is the number given to record the size of an earthquake. For example, a magnitude 5.5 is considered moderate. Above 8.0 is considered a major earthquake and we see one every year or two. Earthquakes measured at 2.5 or less are usually not felt, but can be recorded. And believe it or not, there are millions that happen each year. You can make a model of a seismograph at home, and we are going to show you how. It's activity time! You can print off directions for this one on our website at learnbright.org. You'll need a cardboard box, string, a plastic cup, a marker, small heavy objects, a long strip of paper, and a friend because this is an activity for at least two people. Now comes the fun part. One friend shakes the box, alternating between hard and soft and slow and fast, while the other friend is pulling the strip of paper through the bottom. Watch the marker as it records the movement. This is exactly what a seismograph does during an earthquake. So, in a way, we have not only created our own seismograph, but our own earthquake as well. Now, we can analyze the data just like scientists. Can you tell how hard the box was shaking based on the line? Can you tell when it was barely shaking at all? You are on your way to becoming a seismologist. A seismologist is a person that studies earthquakes. It's pretty cool to watch the process, but it's even more exciting to do it yourself. You can head on over to our website to get detailed instructions for this activity. Just download the lesson plan and as always have fun! Hope you had fun learning with us! Visit us at learnbright.org for thousands of Hope you had fun learning with us! Visit us at learnbright.org for thousands of free resources and turnkey solutions for teachers and homeschoolers.The collision of oceanic and continental crust as well as the collision of two oceanic crust results in the formation of trenches and volcanic arcs. This will also result in the generation of earthquakes, tsunamis and volcanic eruptions. Earthquakes are generated when a fault on the edges of the plates occurs. That is, part of the edges of the plate breaks. The breaking causes shaking on the plates that are felt on the surface. This shaking is what we call earthquakes. When part of the plate breaks during the collision, shifting of the ocean floor happens. During the shifting, energy is released. This energy pushes the ocean water above. When this ocean water reaches the shores, we call them tsunami. During subduction, as plates reach the mantle, it will eventually be melted as magma. When these magmas find a weak spot in the crust, it forms a volcano. This volcano erupts when the crust cannot withstand the pressure exerted by the magma. Earthquakes, Tsunamis, and Volcanoes oh my!Earthquake Hazards There are so many things that can happen during or after an earthquake. There are surface rupture and physical damage to buildings and other infrastructures, liquefaction, fire, landslide, and tsunami. Surface rupture and physical damage is the most obvious hazard of an earthquake the ground to break and buildings to collapse. Urban areas would experience more Earthquakes with higher energy create stronger ground motion, which can cause of this damage due to the presence of more infrastructures. Liquefaction occurs in areas where the soil becomes saturated with water. During an earthquake, the movement of the ground may loosen the soil and allow more water to seep in between the particles. This decreases the ability of the soil to support structures that are resting upon it. When it can no longer support a building, instead of being toppled over, the building starts to sink. Liquefaction mostly occur in reclaimed lands, which were once a part of a body of water. Fires can break out during or after an earthquake due to damaged or broken utility lines, substations, and power plants. It can also occur when ground rupture breaks gas tanks or pipes that lead to gas leaks. Tsunami or a harbor wave is an earthquake hazard that is generated when earthquakes occur on the seafloor. Tsunami displaces large volume of water from the sea to the land, causing damages in the cities and communities near the shore (figure 4-2).Earthquake Hazards There are so many things that can happen during or after an earthquake. There are surface rupture and physical damage to buildings and other infrastructures, liquefaction, fire, landslide, and tsunami. Surface rupture and physical damage is the most obvious hazard of an earthquake the ground to break and buildings to collapse. Urban areas would experience more Earthquakes with higher energy create stronger ground motion, which can cause of this damage due to the presence of more infrastructures. Liquefaction occurs in areas where the soil becomes saturated with water. During an earthquake, the movement of the ground may loosen the soil and allow more water to seep in between the particles. This decreases the ability of the soil to support structures that are resting upon it. When it can no longer support a building, instead of being toppled over, the building starts to sink. Liquefaction mostly occur in reclaimed lands, which were once a part of a body of water. Fires can break out during or after an earthquake due to damaged or broken utility lines, substations, and power plants. It can also occur when ground rupture breaks gas tanks or pipes that lead to gas leaks. Tsunami or a harbor wave is an earthquake hazard that is generated when earthquakes occur on the seafloor. Tsunami displaces large volume of water from the sea to the land, causing damages in the cities and communities near the shore.Earthquakes are generated when a fault on the edges of the plates occurs. That is, part of the edges of the plate breaks. The breaking causes shaking on the plates that are felt on the surface. This shaking is what we call earthquakes. When part of the plate breaks during the collision, shifting of the ocean floor happens. During the shifting, energy is released. This energy pushes the ocean water above. When this ocean water reaches the shores, we call them tsunami. During subduction, as plates reach the mantle, it will eventually be melted as magma. When these magmas find a weak spot in the crust, it forms a volcano. This volcano erupts when the crust cannot withstand the pressure exerted by the magma. Earthquakes, tsunami and eruption of volcanoes are natural disasters brought by the activity of the subduction zone. These natural disasters may cause the loss of lives, damage to properties, displacement to other areas, and livelihood.Important Preparations Before an Earthquake Strikes • Follow the structural design and engineering practices when constructing a house or building. • Evaluate the structural soundness of the buildings and houses: strengthen if necessary. • Be aware of the earthquake evacuation plans for all of the buildings you occupy regularly. • Strap or bolt heavy furniture and cabinets to the wall to keep them in place. • Breakable items, harmful chemical, and flammable materials should be stored properly in the lowermost secure shelves • Prepare and know where fire extinguishers, first aid kits, alarms, and communication facilities are located and learn how to use them beforehand. • Pick safe places in each room of your home, workplace, and school and practice doing drop, cover, and hold.Essential Things to Do While an Earthquake is Happening • Stay calm. • Duck under a sturdy desk or table and hold onto it. Protect your head with your arms. • If there is no sturdy furniture, sit on the floor in a corner next to an interior wall and cover your head and neck with your arms. • Move away from glass windows, sliding doors, shelves, cabinets, and other heavy objects. • Grab anything handy to shield your head and face from falling debris and splinting glass. • Stay indoors until the shaking stops. If you must leave the building. use the stairs rather than elevators. • Stay away from trees, power lines, posts, and concrete structures and proceed cautiously to an open area. • Move away from steep. slopes, which may be affected by landslides. • Move quickly to higher grounds since tsunamis might follow • Pull over to a clear location and stop. Avoid bridges, overpasses, and power lines, if possible. • Be updated about disaster. prevention instructions from battery operated radios.Essential Safety Measures After an Earthquake • Check yourself and others for injuries. • Do not panic. • Expect and prepare for aftershocks. These aftershocks may be weaker but they may sometimes cause more damage than the major earthquake. • Look for emergency supply kits. They should include food, water, medication, clothing, and other things you may need. • If you need to evacuate, leave a message stating where you are going • Do not enter damaged buildings since they might have weakened foundations, increasing their susceptibility for collapse. There can also be a lot of falling debris. • Do not use elevators • Check water and electrical lines for damages. Turn the main switch off to avoid any incidences of electric shock • Look for and extinguish fires to reduce their chances of spreading. • Avoid fallen power lines. • Tune in to radio broadcasts and be updated on disaster prevention instructions.