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Transcript
Name:_________________________________________ Homeroom:___________________________ Date:____________________________________ Study Guide Unit Test Study Guide: _________________ Geology __________________ Use the summary points below as a resource to help you study for our unit test at the end of the un EXPLORING & CALCULATING DENSITY: Density is a measure of how much mass there is in a volume of a substance. You can find the density in three different ways: o Using the formula. o If you would like to find out the density of an odd-shaped object and you have a graduated cylinder filled to let’s say 4 mL – drop the odd-shaped object into the graduated cylinder. The difference between 4mL and the new measurement on the graduated cylinder would give you its volume. You could use a balance to obtain the mass, then use the above bullet for the density equation. o Take two or more liquids and place them in a container together to see which is more or less dense. The liquid(s) that are closer to the bottom are more dense. The liquid(s) that are closer to the top are less dense. least dense (floats) most dense (sinks) EARTH’S LAYERS: Facts About the layers of the Earth: The four main layers of the Earth: Density, temperature and pressure increases as you move inside the Earth from the crust. The crust includes dry land and the ocean floor. The crust and inner core are made of solid rock. The outer core is liquid. The mantle is the largest layer and is broken up into three layers, which are upper mantle (solid), asthenosphere (molten/melted rock) and the lower mantle (mostly solid). The outer core is made of liquid nickel while the inner core is made of solid nickel and iron. CONVECTION CURRENTS IN THE MANTLE: Heat from the core and lower mantle causes convection currents in the mantle. The process works like this: 1. The lower mantle and core heat up the magma in the asthenosphere. 2. The magma rises once it is heated b/c it is less dense. 3. Since the lithosphere is composed of the two coolest layers, when the magma rises it is cooled off by the lithosphere, so it sinks b/c the cooling has made it more dense. 4. The process starts all over again. lower THEORY OF PLATE TECTONICS: The theory of plate tectonics explains the formation, movement and subduction of Earth’s plates. or come together causes the formation of mountains (continental crust) causes volcanoes to form (oceanic + continental crust) this is subduction!!! slide past each causes stress in the crust causes earthquakes when stress is released DRIFTING CONTINENTS: Scientist Alfred Wegener hypothesized that all continents had once been joined together in a single landmass and have since drifted. Wegnener used four pieces of evidence to support his hypothesis: The continents fit together like puzzle pieces. We call this supercontinent Pangaea. He found fossils of tropical animals and plants in arctic places. He collected evidence of historic climate data indicating an ice age had indeed taken place – movement of the poles. He noticed that the pattern of mountains on different continents lined up perfectly if you put the continents together like puzzle pieces. FORCES IN THE EARTH’S CRUST & FAULTS: When Earth’s plates move, rocks are pushed and pulled. The pushes and pulls are called stress. There are 3 types of stress in the crust: divergent movement rock is pushed together convergent movement rock slides past each other transform movement Faults usually occur along plate boundaries, motion push or pull the crust so much that the crust types of faults: normal faults, reverse faults and Over millions of years, the forces of plate movement can landforms such as mountains. Strike-slip fault Rock is pulled apart reverse fault plates move apart other cause mid-ocean ridges cause sea-floor spreading you can get volcanoes & mountains this way normal fault where the forces of plate breaks. There are three main strike-slip faults. change a flat plain into EARTHQUAKES: When tension builds up in the Earth’s crust, sometimes an earthquake happens along with a fault. Earthquakes are measured using seismographs. We use the information from the seismograph to assign the earthquake a number on the Richter Scale. During an earthquake, seismic waves cause the seismograph to vibrate. The recording of the level of vibrations (magnitude) helps scientists to determine the severity of the earthquake. Seismic waves carry energy from the focus, through rock in the crust and onto the Earth’s surface. There are 3 types of seismic waves: primary waves compress and expand like an accordion; they move the fastest of the three types secondary waves vibrate from side to side or up and down in an “s” motion surface waves roll the ground with a wave-like motion. They are the slowest, but most destructive! VOLCANOES: Volcanoes can occur as a result of divergent and convergent plate movement. They can also occur in hot spots. A hot spot is an area of volcanic activity that is not near a plate boundary. When a hot spot forms under a tectonic plate, the hot spot stays in one place, while the plate moves slowly over it. This movement produces a chain of volcanoes. The Hawaiian Islands are a chain of volcanoes that formed this way. hot spot crust Volcanoes mostly occur at convergent boundaries where continental meets oceanic crust. The more dense oceanic plates sink underneath the less dense continental plates. This is called a subduction zone. The edge of the oceanic plate sinks into the mantle and melts. The pressure and heat then build in this area, push through the mountain made from the convergent plates and eventually will erupt to form a volcano (because pressure builds up). There is no difference between lava and magma. We just call it magma if it is below Earth’s surface and we call it lava once it reaches Earth’s surface. The Ring of Fire is an area in the Pacific Ocean that has many earthquakes and volcanoes. The map below shows the Ring of Fire. You can see that it matches plate boundaries around the edge of the pacific ocean. Nearly 75% of Earth’s volcanoes are located along the Ring of Fire. SEA-FLOOR SPREADING In sea-floor spreading, the sea floor spreads apart both sides of a mid-ocean ridge as new crust is added. As a result, the ocean floors move like conveyor belts, carrying the continents along with them. Where the sea-floor separates (fault), ridges form on both sides. We call these ridges mid-ocean ridges since they happen in the middle of the ocean floor. Sometimes the lava can cool over the fault and that area becomes a volcano. The oldest portion of the sea floor would be found farthest away from the mid-ocean ridge. While the newest portion of the sea floor would be the part closest to the mid-ocean ridge. Earth doesn’t grow or expand b/c as the sea floor moves apart in one area, on both sides there are subduction zones sucking the ocean floor underneath the Earth to be recycled again because of density. WEATHERING, EROSION & DEPOSITION: MINERALS: Weathering breaks it down! Erosion carries it away! Deposition piles it up and that is where it stays! Weathering – the breaking down of rock into sediments by ice, water or wind Two types: mechanical or physical Minerals – naturally occurring solids that have a definite crystal shape and structure Minerals are classified in five ways which are: LUSTER Cleavage & Fracture How a mineral reflects How the mineral breaks HARDNESS The results of scratching a mineral against another COLOR STREAK The powder that a mineral leaves behind when rubbed across a surface A mineral’s color The ROCK CYCLE: The rock cycle describes how rocks are formed. All rocks are made up of sediments plus at least one type of mineral. There are three types of rocks. They are: Igneous Rocks formed by heating and cooling of molten/melted rock Extrusive – formed on Earth’s surface by lava Intrusive – formed inside Earth’s surface by magma Example: granite, obsidian Sedimentary Rocks formed by piling up of sediments into layers (compaction & cementation) Can form on water or land Form from other rocks being weathered Metamorphic Rocks formed by heat and pressure below Earth’s surface All metamorphic rocks were previously some other type of rock (sedimentary or igneous) Example: marble, gneiss Example: sandstone, limestone SOIL: Soil is a mixture of weathered bedrock plus humus (decayed organic material) Bedrock - (the Earth’s crust that has not been weathered) Organic – any material that was is living or a part of something living THE LAW OF SUPERPOSITION: The law of superposition states that younger sedimentary layers pile up on top of older layers. Scientists use the order of the layers to make inferences about the Earth’s history. Index fossils are fossils that date a certain period in history. A fossil’s age is the same as the layer where it is found. Horizon O Intrusions are cooled magma that has oozed out of the asthenosphere and lays across or touches already existing sedimentary layers. An intrusion is ALWAYS YOUNGER than any layer that it touches or cuts across! Regular sedimentary layers: Sedimentary layers with an intrusion: