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Transcript
PLANET EARTH TOPIC 1 - MINERALS What is a mineral A mineral is an inorganic, naturally occurring substance. • • Minerals can be elements (pure substances) or compounds (two or more elements) All rocks are made of one or more minerals Classifying Minerals We can classify minerals using the following methods: 1. Lustre - The shininess of a mineral 2. Colour 3. Streak – The colour of a minerals streak when you scratch it 4. Cleavage and Fracture – How a mineral breaks What is a rock • A rock is a natural material made of one or more minerals What is an element • A pure substance that can’t be broken down into simpler parts by chemical means TOPIC 2 – ROCKS AND THE ROCK CYCLE Igneous Rocks • • Igneous rock forms when hot magma cools and solidifies Obsidian and basalt (used in BBQ’s) are two types of igneous rocks Sedimentary Rocks • Rocks made from sediment or loose material • Sandstone and shale are types of sedimentary rocks Metamorphic Rocks • • Metamorphic rocks are formed when heat and pressure change the parent rock into a new rock Schist and marble are types of metamorphic rocks Rock Cycle Rocks continue to change in an ongoing process called the rock cycle Sediment and Soil Soil is formed by: • Rock and rock fragments (sediment) • Plants and animals add organic matter on top of the rock and sediment • The above combine to form soil Humus – Dark, nutrient rich soil • Humus is important in healthy soil TOPIC 3 – EROSION Erosion The movement of rock and mineral grains from one place to another. Rock and minerals are broken down through weathering There are three types of weathering: 1. Mechanical Weathering • • Physical break up of rock Examples of this are freezing and cracking and gravity causing rocks to fall and break 2. Chemical Weathering • Break down of rocks and minerals through chemical reactions • An example of this is through acid rain 3. Biological Weathering • Break down of rocks and minerals caused by living organisms • An example of this is when roots grow through rocks and break the rock apart The Changing Surface of Earth Some common causes of change on the Earth’s surface are: 1. Glaciers – glaciers erode the land by scraping it 2. Gravity – gravity causes landslides and rock slides 3. Wind – wind picks up small bits of material that wear down rock by abrasion 4. Water – moving water erodes soil and rock TOPIC 4 – THE MOVING CRUST Layers of the Earth • • • • The thinnest layer is the crust and is where minerals and oil and gas are formed The mantle is the thickest section – the upper part is solid the lower is liquid The outer core is hot and liquid The inner core is solid...Why would this be solid while the outer is liquid? The high pressure of the outer layers makes it solid Continental Drift A theory that says the continents have slowly changed positions over time Evidence for Continental Drift 1. If you look at the shape of the continents, they look as though they once fit together. 2. Fossils of the same plants and animals were found on different continents. Therefore it was concluded that the continents must have been closer together at some time. 3. Scientists also discovered that similar types of rocks were found on different continents. 4. Coal beds are found on different continents in moderate to cold weather climates. However, coal forms in areas rich in plants that are normally found in warm climates. Therefore they must have been in warmer areas before and moved. The theory of Continental Drift was made by the scientist Alfred Wegner Theory of Sea Floor Spreading A theory that states that new rock is being produced at the mid ocean ridges and that rock moves out, away from the ridge. The Theory of Plate Tectonics A theory that states that the Earth’s crust is broken up into pieces called plates. These plates then move on the Earth’s mantle. This is science’s best theory to explain volcanoes, earthquakes and mountains. What causes the Earth’s Crust to move Convection Currents • • A convection current is the rise of warmer materials followed by the sinking of cooler materials. This happens in the mantle. Scientists believe this is why Earth’s plates move. Why Plates Diverge and Converge (subduction) • • Where convection currents heat up, rise and move away you get diverging plates. Where convection currents cool, fall and move towards each other you get converging plates or subduction. Diverging Plates and Subduction Zones The Earth’s Tectonic plates move in two different ways: 1. Molten lava rises to the surface at ocean ridges causing the plates at ocean ridges to move away from the ridge – This means the plates diverge here. Where continental plates move away, a rift valley is formed. 2. Where the ocean plates hit the continents, they move under the heavier continental plates – This is called a subduction zone. Subduction zones occur near the shores of the continents or where one continental plate goes under another continental plate.