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Transcript
FORCES ON EARTH An investigation into how Newton’s Laws of Motion are applied to the tectonic activity on Earth. GEOLOGY Geologists – scientists who study the forces that make and shape the Earth Geologists divide the forces that change the Earth into two categories: •Constructive – shape the earth by building up mountains and landmasses • Destructive – slowly wear away mountains and every other feature on Earth SO….HOW DO WE KNOW WHAT’S INSIDE THE EARTH? • Geologists record seismic waves and study how they travel through the medium of Earth. • The speed and the path the waves takes reveal how the planet is put together. A JOURNEY TO THE CENTER OF THE EARTH • The further “in” you go… temperature and pressure both increase • There are three main layers that make up the Earth’s interior: • Crust • Mantle • Core THE CRUST • The layer of rock that forms Earth’s outer skin • It consists of about 10 miles of rock • Continental crust is thicker than oceanic crust • However, oceanic crust is much denser than continental crust THE MANTLE • The mantle extends to a depth of approximately 1,800 miles • It is made of a thick solid rocky substance • The uppermost part of the mantle and the crust together form a rigid layer called the lithosphere • The asthenosphere is super-heated rock (molten) • The remainder of the mantle is solid Upper mantel Lower mantel Lithosphere (hard) Asthenosphere (soft) Mesosphere THE CORE • Consists of two parts • Outer core – molten iron and nickel metal • Inner core – solid dense ball of iron and nickel metal CONVECTION CURRENTS AND THE MANTLE • Heat is transferred through: • Radiation • Conduction • Convection RADIATION • Radiation – transfer of energy by electromagnetic waves (ex. Sun heating the Earth) CONDUCTION • Conduction – heat by direct transfer of particles of matter CONVECTION • Convection - The transfer of heat energy by movements of a fluid. • The heating and cooling of a fluid, changes in the fluid’s density, and the force of gravity combine to set convection currents in motion. • Convection currents continue as long as heat is added! CONVECTION IN THE MANTLE • Heat from the Earth’s core and from the mantle itself cause the convection currents in the mantle • Convection currents are an unbalanced force that causes heat flow and the movement of material within the earth. • This moving material results in earthquakes and volcanic eruptions to create mountains and ocean basins. TECTONIC PLATES – WHAT ARE THEY? • The crust is broken into large pieces, which we call “plates” PLATE MOVEMENT • Plate movement result in stress within the Earth’s crust which adds energy to rock until the rock either breaks or changes shape PLATES AND FORCES • Plates apply equal and opposite forces on each other. (A push or pull ) • The acceleration of the plate depends on forces acting on the plate and the mass of the plate. http://education.sdsc.edu/optiputer/flash/co nvection.htm EFFECTS OF PLATE TECTONICS *There are several geological processes that occur where plates meet (at the plate edges): 1. Volcanoes tend to erupt at plate margins as a result of a process called subduction 2. Earthquakes occur where plates grind against or over one other 3. Mountain building occurs as one plate is pushed over another 4. Seafloor spreading occurs where two oceanic plates pull apart, makes ocean basins THE 3 TYPES OF PLATE BOUNDARIES “Convergent, means to come together.” CONVERGENT BOUNDARIES • Convergent Boundaries are the boundaries between two plates that are converging, or moving towards each other. • Earthquakes, island formation, mountain forming, and volcanoes all occur as the result of these plate collisions. • When two plates collide (converge) one plate moves under the other. This process is called “subduction.” • There are three types of convergent boundaries TYPES OF CONVERGENT BOUNDARIES Oceanic/oceanic Subduction occurs Oceanic/continental Oceanic plate sinks Continental/continental Mountain ranges form Convergent boundary of two oceanic plates. Creates an island arc and a trench. A trench is like a deep canyon, but in the ocean. Example: Japan The most famous trench in the world: Mariana Trench Oceanic plate and a continental plate. Forms a volcanic mountain range and a trench. Example: Andes Mts ContinentalContinental Boundary The convergent boundary of the Eurasian and Indian Plates has resulted in the formation of the highest mountain range in the world – The Himalayas This illustration shows the movement of the land mass known as India today. As it moved on the Indian plate through time, over millions of years, it finally collided with the Eurasian plate forming the Himalayan Mountains Mount Everest is the tallest mountain in the world, at over 29,000 ft. and is part of the Himalayas. This is a result of the Eurasian and Indian Plates colliding and it is still getting higher as these two plates continue to collide. DIVERGENT BOUNDARIES • Divergent Boundaries are the boundaries between two plates that are diverging, or moving away from each other. “Divergent, means to spread apart.” When plates are spreading apart from one another there is a lot of geological activity. Earthquakes and volcanoes occur here. •In some places like in East Africa, a rift valley can form that is hundreds of feet deep. Aerial view of Africa’s Rift Valley The Mid-Atlantic Ridge is one of the world’s largest divergent plates, running North to South in just about the center of the Atlantic Ocean. All along this ridge, volcanic activity takes place and the sea floor is spreading East and West at a rate of 1.25 cm per year. Question: So what is happening on the other side of that same plate? Divergent Boundary Between the Eurasian and North American Plate TRANSFORM FAULT BOUNDARIES • Transform Boundaries are the boundaries between two plates that are sliding horizontally past one another. “Transform, means to slide past one another.” PLATES MOVE SIDE BY SIDE • Transform boundaries neither create nor consume crust. Rather, two plates move against each other, building up tension, then releasing the tension in a sudden and often violent jerk. This sudden jerk creates an earthquake. Earthquakes in Austin Strike Slip Faults Transform-fault boundary where the North American and Pacific plates are moving past each other. Example: San Andreas fault in California The San Andreas Fault, seen here, is the result of the Pacific Plate sliding past the North American Plate. This is the site of many of the earthquakes that occur in the United States CHANGING EARTH’S SURFACE • Plate movement can alter Earth systems and produce changes in Earth’s surface • Deformation of the crust • Faults • Mountain building • Land subsidence • Volcanoes VOLCANOES • A volcano is a weak spot in the crust where molten, rockforming magma comes to the surface • Volcanic activity builds mountains made of lava rock and other volcanic materials LOCATION OF VOLCANOES • There are more than 600 active volcanoes on land and many more beneath the sea • Volcanic belts form along the boundaries of Earth’s plates. • One major volcanic belt is the Ring of Fire RING OF FIRE Ring of Fire – very active region of subduction http://www.vo lcano.si.edu/p layers.cfm?pid =2 RECENT EARTHQUAKES AND VOLCANIC ERUPTIONS WHAT ARE HOT SPOTS? • All seismic activity occurs along plate boundaries (except for hotspots) • Magma rises through the mantle forming an active volcano • The plate moves over this spot forming a chain of islands with the active volcano being the one over the hot spot Hot Spot Volcanoes HOW IT WORKS WEB-QUEST! • Get a computer and begin working on the web-quest. • Follow the questions and it will lead you through the online activities. • This is due – A day: 3/12 B day: 3/13