Earth Science

Define the following terms: Continental drift theory: the separating of continents by drifting across the oceans Theory of plate tectonics: The theory that the Earth’s crust is broken into many large pieces that move on the mantle Seafloor Spreading: The process of new crust forming at the ocean ridges and spreading outwards. Caused by divergent plate boundaries. Subduction: Where one crust sinks beneath another crust, caused by converging plate boundaries. Continental crust: The crust that forms the continents. This is thicker, but less dense than oceanic crust. Oceanic crust: The crust that forms the ocean floor. It is thinner, but more dense than continental crust. Converging boundary: Where plates are moving towards each other, colliding together. Causes some crust to be melted into the mantle and lost, therefore also called destructive boundaries. Diverging boundary: Where plates are moving apart from each other in opposite directions. Causes magma in the mantle to rise and form new crust, therefore also called constructive boundaries. Transform boundary: Where plates are sliding parallel to each other, but in opposite directions. No crust is created or lost, therefor also called conservative boundaries. Earthquake: The rapid movement of the ground, usually back and forth and up and down in a wave motion due to the movement of the earth’s crust. Epicentre: The point on the Earth’s surface directly above the focus of an earthquake. Focus: The place below the ground where the earthquake starts. Hot spots: isolated places away from plate boundaries where a lot of hot magma is created. Seismometer: An instrument that detects seismic waves from an earthquake to measure the earthquakes intensity. Volcano: Natural opening in the Earth’s crust connected to areas of molten rock (magma) deeo inside the crust. Volcanic eruption: Event that causes lava to flow from vents and red-hot fragments of rock, dust, ash and gases shoot out of crater of a volcano. Crust: Outermost layer of the earth, includes landforms, rock and soil. Mostly made up of rock. Varies in thickness from 5km-70km. Mantle: Located underneath the crust of the Earth, made up of molten rock, temperatures between 500C and 2000C. Approximately 2900km thick. Pangea: The former ‘super continent’ that once existed that included all of the land masses of the earth, thought to have existed before the continents broke apart. Laurasia: Supercontinent of the Northern Hemisphere Gondwana: Supercontinent of the Southern Hemisphere Fold: buckling of rocks caused when rocks are under pressure from both sides Fault lines: a break in a rock structure causing a sliding movement of the rocks along the break After shocks: A smaller earthquake following the main shock of an earthquake. OUTCOME1: Identify the structure of the Earth (crust, mantle, inner and outer core) and its composition 1. Label the Earth’s layers on the diagram below and state two facts about each. 2. Name the two types of crust that form tectonic plates and explain how they are different. Continental crust – between 30km-70km thick, it is the parts of the Earth’s crust that make up the land. Oceanic crust – Thinner and denser than continental crust, it is the parts of the Earth’s crust beneath the ocean. 3. Explain why the Earth’s core is not molten even though the temperature is thought to be as high as 7000⁰C. The iron in the Earth’s core is under a huge amount of pressure from the layers above it causing it to be a solid rather than a liquid. OUTCOME2: Understand that the Earth’s crust is divided into plates 1. Describe the theory of plate tectonics The theory of plate tectonics states that the Earth’s crust is divided in to plates of varying sizes and that these plates are slowly moving. 2. What is the name of the plate Australia is located on? Indo-Australian Plate OUTCOME3: Understand the movement of tectonic plates is due to convection currents in the mantle 1. Explain how something as large as tectonic plates can be moved. Due to the convection currents in the mantle. The magma found in the mantle that is closest to the outer core is exposed to high temperatures making it extremely hot. The hot magma rises to the surface of the mantle which displaces the cooler magma causing the magma at the surface to fall. This creates a convection current which drags the plates of the Earth’s crust causing them to move. 2. What is a convection current? And what drives the convection current in the Earth’s mantle? When a liquid is heated it causes the liquid to expand and become less dense making it rise. As the heated liquid rises it displaces the denser cooler liquid above, making it fall. This convection current in the mantle is caused by the magma in the mantle closest to the outer core gains heat energy from the outer core making it hotter and less dense causing it to rise. The more dense and cooler magma at the surface of the mantle then falls. OUTCOME4: Investigate how the theory of plate tectonics developed 1. What evidence is there to support the theory of plate tectonics? a) Shape of the continents, they are shaped so that they may fit into each other like a jig-saw puzzle, supporting the idea they were once all connected. b) Data obtained from satellites suggests the continents are slowly moving each year. c) Fossils of the same species have been found on different continents and there is no other reasonable explanation of how the same species came to live on various continents other than that they were once connected. 2. Name the person who proposed the ‘Continental Drift’ theory and describe this theory. The theory suggests that the continents are slowly moving and that they were once all together as a supercontinent. This was suggested by Alfred Wegener. 3. Explain how flightless bird fossils have been found on multiple continents. All of the continents once existed as one giant supercontinent called Pangea. The flightless bird lived on this supercontinent and as the continents drifted apart some of the flightless bird population were on the separate land masses. OUTCOME5: Understand the movement of plates at diverging boundaries, converging boundaries and transform boundaries 1. Complete the table below Plate boundary Diagram Description of movement of plates What can movement at this plate boundary cause? Convergent Plates are moving towards each other – colliding with each other. Crust is being destroyed in the process (destructive boundary). Ocean trenches near land and volcanoes near oceans. High fold mountains. Earthquakes. Divergent Plates are moving away from each other. Magma rises to fill the gap left between the plates meaning crust is being formed (constructive boundary). Seafloor spreading, ocean ridges, volcanic activity (under the ocean), shallow earthquakes, rift valleys. Transform Plates are sliding parallel to each other but in opposite directions. No crust is being created or destroyed (conservative boundary). Earthquakes. Folds and Faults in rocks. 2. Describe the process of subduction with the aid of diagrams. Process in which two tectonic plates push against each other, and dense oceanic crust sinks below the less dense continental crust 3. Explain the origin of the Himalayas The Himalayas have been formed as a result of a converging plate boundary whereby two continental crusts have collided creating fold mountains. As the plates continue to move towards each other the height of the Himalayas is growing each year. 4. At diverging boundaries, seafloor spreading is occurring as new crust is continually created. Propose why the Earth’s crust isn’t getting any bigger. The crust being created at diverging boundaries is balanced out by the crust that is being destroyed or melted into the mantle at converging plate boundaries. 5. Explain how deep ocean trenches form near land with volcanic activity close by. Deep ocean trenches form near land with volcanic activity nearby as a result of converging oceanic and continental crust. Subduction occurs is this situation where the dense oceanic crust is pushed under the less dense continental crust. This creates an ocean trench and an area where crust is melted into magma creating extreme heat and a weakness in the Earth’s crust which forms a volcano. OUTCOME6: Recognise that earthquakes occur along fault lines 1. Explain why Australia has few earthquakes. Australia is not located close to any plate boundaries. Earthquakes are mainly caused by movement of tectonic plates at plate boundaries and fault lines. As a result Australia has very few earthquakes. 2. Where are earthquakes likely to occur and why? Along fault lines and near plate boundaries. OUTCOME7: Understand that the focus is where the earthquake takes place underground and the epicenter is immediately on the Earth’s surface where the earthquake hits 1. On the diagram below label the focus, epicenter and fault. 2. List 2 factors that can influence the devastation caused by an earthquake. • How close the epicentre is to the focus (how far below ground the movement occurred) • Distance between the city/town and the epicentre • Population density • Stability of buildings, a large amount of older buildings that have not been designed to withstand earthquakes cause more damage • Magnitude of the earthquake. • Access to health care and emergency services after an earthquake. OUTCOME8: Understand that seismologists study earthquakes and use a seismograph to record the magnitude of an earthquake which is measured on the Richter scale 1. Name the occupation that studies earthquakes. seismologist 2. One earthquake measures 5 on the Richter scale and the other measures 7. Explain what the Richter scale is and how these earthquakes would be different. Scale numbered 0-10 which measures the magnitude/amount of energy released by an earthquake. An increase of 1 means a 30 times increase in energy. Therefore the magnitude 7 earthquake would have 900 times more energy than the magnitude 5 earthquake and there would be 100 times more movement of the earth. A magnitude 5 earthquake would cause mild damage to buildings while a magnitude 7 would cause major damage to many buildings and cause cracks in roads. OUTCOME9: Recognise that volcanoes occur at the melting edge of a subduction zone 1. Outline why there are more volcanoes situated near subduction zones than anywhere else on continental crust. At a subduction zone dense oceanic crust is pushed under less dese continental crust which causes the oceanic crust to come closer to the mantle causing it to melt into magma. This creates a lot of heat under the Earth’s surface and the hot magma bursts to the surface to form a volcano. OUTCOME10: Understand the terms ash cloud, conduit, magma chamber, vent, side vent, eruption, dormant, crater in relation to volcanoes. 1. Use the words below to label the diagram: 2. Describe the difference between a dormant, active and extinct volcano. Active volcanoes - Erupting volcanoes or volcanoes that have recently erupted (within the last 20years) Extinct volcanoes - Those that have not erupted for thousands of years. Considered to be ‘dead’ and unlikely to erupt again. Dormant volcanoes - Volcanoes that have not erupted for over 20years but are not considered extinct. They could still erupt. Considered to be ‘sleeping’.