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The Moving Crust Topic 4 The Moving Crust The crust is the top layer of the Earth. It also includes the minerals in the rocks below it. The Crust The Mantle The Earth’s mantle is made up of a plastic rock layer Plastic means it is melted and gooey, but not completely liquid The mantle can flow, but very slowly. The Mantle The Core The Core of Earth is very hot – around 6000oC The outer core is liquid iron and nickel around 5500oC The intense heat and pressure have made the inner core a solid ball The Core Continental Drift The shape of land is constantly changing. Continental Drift Evidence - Wegener Alfred Wegener was one of the first scientists to question plate movement He formed the Theory of Continental Drift Evidence Evidence – Sea Floor Spreading Evidence - Technology Sonar uses sound wave to make measurements Sonar identified the Mid-Atlantic Ridge Magnetometers detect the direction and strength of a magnetic field The magnetic field of the crust in the Atlantic sometimes pointed south, instead of north these are called reversal strips Mid-Ocean Ridges Evidence - Technology The Theory of Plate Tectonics Technology showed that the Earth’s crust is moving The crust is made up of plates of rock that fit like puzzle pieces Converging plate are coming together Diverging plates are moving apart Canadian Scientist J. Tuzo Wilson also concluded that plates can slide past each other Plate Tectonics Subduction Subduction zones are where plates are converging. Subduction is when one plate slides underneath another. Subduction Plate Tectonics Plate Movement Plate Movement Mariana Arc (& Trench) Earthquakes Topic 5 Earthquakes Earthquakes are caused by sudden movements in the tectonic plates. Seismic is of or having to do with the movement of tectonic plates Seismologists can use seismographs to measure the intensity of an earthquake It is attached to the bedrock to detect vibrations Earthquakes Liquefaction is the process of a solid taking on fluid qualities, like quicksand Tsunamis are huge waves that happen when an earthquake occurs under the ocean (Japanese word meaning 'harbour wave') Avalanches or rock slides occur in mountains as a result of an earthquake Richter Scale Earthquakes are gauged on the Richter scale up to 10. Less than 2 is not generally felt, above 8 totally destroys communities and structures Table 1: Relationship between Richter Scale magnitude and energy released. Richter Scale 2.0 5.0 Energy Release (J) Comment Smallest earthquake detectable by people. 2.8 x 1012 Energy released by the Hiroshima atomic bomb. 7.6 x 1013 About 120 shallow earthquakes of this magnitude 6.0 - 6.9 to 1.515 x 10 occur each year on the Earth. 7.7 x 1014 6.7 Northridge, California earthquake January 17, 1994. Major earthquake threshold. Haiti earthquake of January 12, 2010 2.1 x 1015 7.0 resulted in an estmated 222,570 deaths Turkey earthquake August 17, 1999. More than 12,000 people 7.9 x 1015 7.4 killed. Deadliest earthquake in the last 100 years. Tangshan, China, July 1.5 x 1016 7.6 28, 1976. Approximately 255,000 people perished. 1.6 x 1017 8.3 San Francisco earthquake of April 18, 1906. 9.0 Japan Earthquake March 11, 2011 December 26, 2004 Sumatra earthquake which triggered a 4.3 x 1018 9.1 tsunami and resulted in 227,898 deaths spread across fourteen countries Most powerful earthquake recorded in the last 100 years. 8.3 x 1018 9.5 Southern Chile on May 22, 1960. Claimed 3,000 lives. 1.3 x 108 Seismic Waves Seismic waves are the energy waves that travel outward from the source of the earthquake. Primary Waves Primary or p waves are fastest Can go through solids, liquids and gases. Compression vibrations before an actual earth quake. Secondary Waves Secondary or s waves slower Only pass through solids not liquids or gasses. Surface Waves Surface waves are the slowest Move like ripples - rolling motion Most destructive Created when p and s waves collide Earthquake Location The time between P and S wave can help locate the source of an earthquake The source of an earthquake deep in the crust is called the focus The location directly above the focus is called the epicenter of an earthquake Aftershocks are actually smaller earthquakes from the same focus Earthquakes Earthquake Location Primary waves are bent or refracted as they travel through the Earth The area where they do not come through the other side of the earth is called a shadow zone Think about it! How could the 1995 earthquake in Kobe, Japan have been recorded on Richter scales in Manitoba? Distribution of earthquakes with a magnitude less than 5.0 relative to the various tectonic plates found on the Earth's surface. Distribution of earthquakes with a magnitude greater than 7 on the Richter Scale. Faults Rock located where tectonic plates meet is under very high pressure If the rock is bent or stretched enough the rock can break creating a fault through the crust There are three types of fault movement between the tectonic plates Fault movement creates earthquakes The Big One Faults Normal Faults Tension or pulling action, which breaks rocks apart North Atlantic Reverse Faults Compressive , causing rock to bend break and buckle Marianas Trench, near Japan Slip, Strike or Transform Faults Shear forces causes slipping which and jagged edges break off Pacific Plate Normal Faults Reverse Faults Slip Faults San Andreas