An earthquake is what happens when two blocks of the earth suddenly slip past one another. Geologists, in mapping the rocks at the earths surface, locate the faults fractures and folds plastic bends which are evidence of the mechani cal deformation of rocks in mountain building. This map illustrates 119 years of global seismicity in the context of global plate tectonics and the earths physiography. Earthquakes teacher notes and student activities ga record. The quaternary geology of the seattletacoma urban corridor building the foundation for geologichazard mapping pdf ground motion and site conditions the data obtained from active source studies are archived at iris andor at the national geophysical data center. The lecture will be enhanced if the instructor presents. Global maps show tomographic scans of seismic wave velocities in the upper mantle, a in map view at depths of 100, 300, and 500 km 60, 190, and 310 miles, and b in cross section to a depth of 660 km 410 miles directly beneath the two lines indicated, one that girdles earth. An experience of science theatre to introduce earth interior. That activity builds stress and creates earthquakes. While many countries have borders along faults and mountain ranges, earthquakes dont care about political boundaries. Primarily designed for use by earth scientists, engineers, and educators, this map provides a comprehensive overview of strong magnitude m 5. Earth where rocks failure on the san andreas fault has caused an earthquake. Some surface waves move along earth s surface in a manner that.
That break is the origin or focus of the earthquake. You will learn more about density in a later section. Earthquakes and the earths interior an investigation using. Seismic tomographyusing earthquakes to image earths interior. Layers can be inferred by recording energy from earthquakes. Fault fracture systemzones along which rocks have been displaced fault segment. Some earthquakes originate very far inside earth and are called deepfocus earthquakes, while others are shallower and are called shallowfocus earthquakes. Earthquake vibrations are measured with seismometers. The surface expressions of the release of mechanical energy of mountain building and other earth movements are earthquakes.
Energy moves outward as an expanding sphere of waves. The surface where they slip is called the fault or fault plane. Earth science guided reading and study workbook 55 vocabulary definition earthquake a. The major structural components in the earth that are. If the earth were of uniform composition and density seismic rays would travel in straight lines as shown in figure 1. Some of the energy is left over from the formation of the planet about 4. Earthquakes and the earths interior a violent pulse. Seismic tomographyusing earthquakes to image earths. But our planet is broadly layered causing seismic rays to be refracted and reflected across boundaries. Crust brittle, rocky outer layer of the earth 540 km thick thinnest layer. Lesson 2 allows students to focus on plate boundaries where a large fraction of all earthquakes, volcanic eruptions, and mountain building occur. Each earthquake produces three basic types of seismic waves. Studying them has revealed much information about earths interior. Its like when youre teacher loses their marbles because youve asked them the same question 7 times in a row.
Middlehigh school book title authors description earthquakes and volcanoes ellen prager describes how plate tectonics and shifts in the earths crust cause earthquakes and volcanoes, and explains the danger behind the. The energy earthquakes release travels in the form of waves called seismic waves. Basic structure of the interior of the earth 4 major layers. Our direct knowledge of earth s interior is limited to the first few tens of kilometers immediately below the surface. These vibrations travel laterally as surface waves. Middlehigh school book title authors description earthquakes and volcanoes ellen prager describes how plate tectonics and shifts in the earth s crust cause earthquakes and volcanoes, and explains the danger behind the. In fact, at earths center the temperature is greater than 6000c. Geology 12 earthquakes and earths interior youtube. Earthquakes arent predictable, so the best practice is to always be prepared. This release of energy causes intense ground shaking in the area near the source of the earthquake and sends waves of elastic energy, called seismic waves, throughout the earth. By analyzing these seismic waves, seismologists can explore the earth s deep interior. Earths interior can also be divided into layers based on physical properties.
The dialogue then focuses on earthquakes, seismic and volcanic hazard while emphasizing that risk might be mitigated by preparedness strategies. Energy released at an earthquakes focus radiates outward as body waves, which are of two kinds. What is the principal cause of convection in earths mantle. The location below the earth s surface where the earthquake starts is called the hypocenter, and the location directly above it on the surface of the earth is called the epicenter.
Studying them has revealed much information about earth s interior. Causes of earthquakes earthquake hazard and emergency management 24 objective 2. Earthquakes and earths interior summary abrupt movements of faults that release elastically stored energy cause earthquakes elastic rebound. Evidence of a restless planet california academy of. The movement of earths crust resulting from the release of built up potential energy between two stuck tectonic plates. Earthquakes and volcanoes make the following foldable to help you compare and contrast the characteristics of earth quakes and volcanoes. California academy of sciences earthquake educator guide 09 c. Physical processes of the earth in lesson 1 students learn about the earths interior and plate tectonics, which is the driving mechanism for earthquakes. Earthquakes occur when energy stored in elastically strained rocks is suddenly released. An earthquake is the result of the sudden release of builtup stresses within the earths crust, which is recorded with a seismograph.
Develop an understanding of the structure of the earths interior by constructing a scale model of a slice of the interior of the earth and study the material properties of the earths interior. Earthquake earthquakes are sudden, violent shaking of the earths crust. Earthquakes occur when rock in this layer breaks andor moves there are two major types of crust. The science behind earthquakes what is an earthquake. Earthquakes create seismic waves that travel through the earth. The geological society earthquakes information on the basics of earthquakes.
Earthquakes of magnitude 3 or lower are mostly imperceptible, while quakes of magnitude 7 and above cause serious damage over large areas. The topmost part of the mantle is cooler than the parts below. Many earthquakes happen at the borders of tectonic plates. Major tectonic plates on the earths surface the earth and its interior long time ago, a large collection of material masses coalesced to form the earth. These are smaller earthquakes that happen in the same place as the larger earthquake that follows. Focus point where strain is released along a fault deep in earth interior.
First predicted earth quakeuake, few deaths, few deaths earthquakes accelerationshaking of ground caused sudden release of strain rupture along faults. Much of what we know about earths interior comes from waves generated by earthquakes. Some surface waves move along earths surface in a manner that. This fact sheet uses data from the 1994 magnitude 6. Large amount of heat was generated by this fusion, and slowly as the earth cooled down, the heavier and denser materials. Draw a volcano on one flap and label the flap volcanoes. Mediumfocus earthquakes are neither on earths surface nor deep in earth. Earthquakes are the sudden shaking and vibrating of the earths crust as a result of a rapid release of energy when rocks break and move along faults. Turn the paper horizontally and fold the outside edges in to touch at the midpoint mark. This is the energy that causes earthquakes as well as slow deformation of the crust. Also, the seismic waves from earthquakes can be used to image the deep interior of the earth, providing vital clues to the internal structure of our planet. Most of the damage from earthquakes is associated with. Earthquakes and the earth s interior earthquakes earthquakes occur when energy stored in elastically strained rocks is suddenly released. A the initial fault rupture started about 32 kilometers below the seafloor red dot and propagated to the west dashed red line, causing severe ground shaking in the miyagi prefecture.
A fault is a fracture or crack in the rocks where one side has moved relative to the other figure 1. It is best to download a large pdf file to your hard drive rather than open it inside your browser. The focus and epicenter of an earthquake can be located by measuring the differences in travel times between p and s waves. Learn vocabulary, terms, and more with flashcards, games, and other study tools. The activity is on page 5253 of the revised august, 2000 edition of tremor. Use this map to sketch the approximate locations of the major plate boundaries and name the plates. The geological society earthquakes 101 slideshow pdf pdf format of a complete powerpoint show for the basics usgs earthquakes by bruce a. Earthquake energy also causes earth s surface to vibrate. By analyzing these seismic waves, seismologists can explore the earths deep interior. Use colored pens, pencils, or crayons to plot the earthquakes from table 1 on the graph on. Earthquake summary posters for significant earthquakes. The lecture will be enhanced if the instructor presents electronic slides or overheads of the visuals below. British geological survey earthquakes 101 slideshow pdf pdf format of a complete powerpoint show for the basics usgs. Leftslip and rightslip faults are types of strikeslip faults.
Learning earthquake tip 1 earthquake design and construction. Surface waves are the slowest and largest of the seismic waves, and they cause most of the destruction during an earthquake. Faults can be identified by the offset of rock layers on either side of the fault surface. As you move from the crust to the interior of earth, there is an increase in the temperature, pressure, and density of the materials. Many earthquakes happen because of stress on local areas of rock. Much of what we know about the earths interior comes from waves generated by. Earthquakes occur when rock in this layer breaks and or moves there are two major types of crust. The movement of earth s crust resulting from the release of built up potential energy between two stuck tectonic plates.
Earth quakes reading earthquakes earthquakes provide evidence of earths structure, which includes the core, mantle and crust. The amount of energy released during an earthquake can vary by very large amounts. Earthquake waves diminish in intensity the further they travel, so the further you are from the epicenter the point on the earths surface where the earthquake wave first strikes the less intense is the shaking from the earthquake. When the stress builds to a level that is too high, the rock gives way, snaps, and breaks. Earthquakes represent the vibration of earth because of movements on faults. The location below the earths surface where the earthquake starts is called the hypocenter, and the. Earthquakes provide evidence of earths structure, which includes the core, mantle, and crust. Earthquakes and the earths interior earthquakes earthquakes occur when energy stored in elastically strained rocks is suddenly released.
There is a large amount of geologic activity and movement along the borders of these plates. Earthquakes in the central united states16992002 usgs. Earth s layers can be examined indirectly, such as by studying earthquakes, magnetism, gravity, and heat flow and by applying the laws of physics. Earthquakes podcasts, presentations and fact sheets on the basics of earthquakes. Of the choices, volcanic activity was a good cause of earthquakes. Normal and reverse faults are types of dipslip faults. There are two principal sources of earths internal heat energy.
Before an earthquake during an earthquake after an earthquake for more information on earthquake. It is a large fault zone that separates two great sections of earths crust. Finally, axels fear is relieved while aurora envisages an earth without earthquakes and volcanoes. Draw a mark at the midpoint of a vertical sheet of paper. They are caused when the earths tectonic plates move, rub, collide, or break apart. Bolt online companion links related to subjects covered in book w. Textonly pdf 69 kb this version of the report is accessible as defined in section 508. Most earthquakes occur at depths of less than 80 km 50 miles from the earths surface moonquakes earthquakes on the moon occur, but they happen less frequently and have smaller magnitudes than earthquakes on the earth.
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