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Term Test 1 Review.docx

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Earth Science
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TERM TEST 1 REVIEW SHEET Lecture 2: SCIENTIFIC METHOD Name and describe the steps of the scientific method (including observations, hypotheses, predictions and tests). Be able to give or analyze some examples. - observation o collecting data through observation and measurement - hypothesis o a hypothesis is an untested explanation/best guess for how or why things happen in the manner observed - prediction o method of testing hypothesis based on hypothesis - testing o conduct experiment to test hypothesis and collect more data - evaluation o consists of hypothesis acceptance, rejection, or modification o acceptance if prediction works o rejection if prediction doesn’t work o modification if prediction doesn’t work but you’ve got a good idea why Describe the difference between a theory and hypothesis. - hypothesis o a highly educated guess, informed by lots of observations o the best, although unproven, explanation for a phenomenon - theory o a hypothesis which has survived exhaustive testing and the defeat of competing hypotheses Explain some of the special difficulties faced by geologists in applying the scientific method. - only partial information is available - processes can only be observed as they are acting now o they may have been different in the past - time and space scale for many processes much too large to observe o can’t design a practical experiment Explain some of the techniques geologists use to get around these difficulties, such as computer models, laboratory experiments and natural experiments (for example, for understanding the structure of the earth). - natural experiments o certain seismic waves shouldn’t be able to pass through liquid o wait for an earthquake and observe - lab experiments o if the conditions of the outer core are recreated in the laboratory, iron should be liquid - computer models o computer model that builds in everything we know about physics, chemistry and the composition and conditions of the interior of the earth will predict a liquid outer core Lecture 3: FORMATION OF THE UNIVERSE, SOLAR SYSTEM AND EARTH Describe what happened after the big bang, and how that led to the formation of galaxies. - the universe began to expand at a constant rate - the explosion caused matter to initially be distributed inhomogenously o lumpiness; wasn’t smooth - over time, lumps of denser matter became centers of high gravity and began to grow - eventually the lumps became large group of stars and eventually galaxies o large groups of stars are called galaxies Explain why the solar system rotates. - because of leftover momentum from the solar nebula that all the planets and the sun formed from Describe the formation of the solar system, including the formation of the sun, the rocky inner planets and the gaseous outer planets. - a nebula forms from hydrogen helium and heavier elements left from the big bang - the nebula, under the influence of gravity, condenses into a swirling disc, with a central ball surrounded by rings o as it condenses, it begins to spin - ball at center grows dense and hot enough for fusion (two hydrogen atoms get together to form helium) o once fusion begins, this becomes the sun - in the rings, dust particles collide and stick together, forming planetesimals - planetesimals grow into the proto-Earth o as it continues to grow, the interior heats up and becomes soft - as the proto-Earth gets bigger, gravity reshapes it into a sphere o interior differentiates  more dense iron-nickel metal moves into core  less dense rock moves outwards into crust Explain the theory for the formation of the moon. - soon after Earth forms, a small planet, about the size of Mars, collides with it o Earth has iron core and so did the body that collided with it o body added iron to earth and some rocky debris got sent into space - debris formed a ring around the planet o the Moon formed from the ring of debris Know the difference between the following: universe, galaxy, solar system. - universe o everything we can see, all the galaxies - galaxy o cluster of stars - solar system o planets which are orbiting around a single sun Know the composition of the sun and the process that causes it to produce heat. - the sun o composed of hydrogen and helium o edges of sun is called corona  stuff that is being ejected from the sun; charged particles - sun causes heat because it undergoes fusion o two hydrogen join to form helium Explain the relationship between solar winds, sunspot activity, the Earth’s magnetic field and the northern and southern lights (aurora). - solar winds o stream of charged particles that reach earth o produced by sunspot - sunspot activity o caused by disruption in the sun’s magnetic field o sun spot has 11 year cycle o affects Earth and the signal of our communications - earth’s magnetic field o deflects soalr wind o some solar winds do reach earth - aurora o interactions of solar wind with earth’s magnetic field o concentrated in polar regions Describe the difference between a gaseous outer planet and a rocky inner planet. Name the gaseous and rocky planets. - inner plants o Mercury, Venus, Earth, and Mars o ‘rocky’ o all have iron core and have rocky sheath around it o Mercury and Mars only have solid inner core o Venus and Earth have both solid inner core and liquid outer core - outer planets o Jupiter, Saturn, Uranus and Neptune o ‘gaseous giants’ o mostly composed of gas and ice Compare asteroids and comets in terms of size, composition and where they are found in the solar system. - asteroids o rocky o more ‘common’ o smaller (<100 km) o travel slower (<180,000 kph) o come from asteroid belt between Mars and Jupiter - comets o icy o less ‘common’ o larger (>100 km) o travel faster (<180,000 kph) o come from the Kuiper belt and Oort Cloud beyond the solar system Define the terms asteroid, meteor and meteorite. - asteroid o large chunk of rock from the asteroid belt between Mars and Jupiter - meteor o an asteroid that has entered Earth’s atmosphere and is burning up o ie. shooting star - meteorite o an asteroid that survived passing through the atmosphere and crashed into earth Explain the hypothesized relationship between a comet and the extinction of the dinosaurs. - 65 million years ago - comet impacted the earth o impact produced tsunami o there would be air blasts (shockwaves), wildfires (because of all the hot debris around), a lot of dust would be ejected into the atmosphere which would block the sunlight for a long time What do scientists think happened? - evidence in rock layers o pre-extinction layer  oldest rock  consists of sediment containing microfossils from the time of the dinosaurs o ejecta layer  contains material blasted from the crater and deposited here within days to months o fireball layer  dust and ask fallout from the asteroid impact o post-extinction layer  youngest rock  sediments containing microfossils from after the dinosaurs Lecture 4: STRUCTURE OF THE EARTH Describe the basic composition, density and thickness of the major layers of the earth: crust, mantle, inner core, outer core. - total radius = 6371 km - crust o 0.5%, 10-70 km - mantle o 67%, 2880 km - core o outer  30.8%, 2260 km o inner  1.7%, 1220 km - crust o made of oceanic crust and continental curst o oceanic crust  crust is about 10km thick  higher density and heaver (3.2g/cm ) o continental crust  crust is about 35km thick  lower density and lighter (2.65g/cm ) - mantle o composition of the mantle (as far as we know) is homogenous; one composition throughout o the mechanical behaviours are different o divided into three regions  lithosphere  crust and uppermost mantle  thick (100-250km thick)  rigid: crust is in contact with atmosphere and the surface of the earth is relatively cold compared to the rest of the layers of the earth o upper part of the mantle is so cold that it becomes solid  asthenosphere  upper mantle  about 200km thick  relatively soft, not much liquid present (ductile)  over geologic time, it can act like a liquid  hot and under less pressure than the rest of the mantle so it is able to flow more easily  rest of the mantle - core o made out of mostly iron o entire core hot enough to melt o inner core is solid  all the way at the bottom of the earth and has all the weight of that rock on it  under so much pressure that it doesn’t melt and stays solid o outer core is liquid  still hot but under less pressure than the inner core Explain how and why meteorites help us understand the composition of the earth. - look at composition of meteorites that hit the earth - we can assume that if planetesimals were formed around the same time as the solar system, they have the same composition as the Earth so we can look at pieces of meteorites and infer the composition of earth - stony meteorites o resemble Earth’s crust - stony-iron meteorites o resemble Earth’s mantle - iron meteorites o resemble Earth’s core Know the age of the earth and how meteorites have been used to determine it. - 4.57 billion years o oldest dated rocks on earth: 4.3 billion years old o oldest meteorites: 4.57 billion years old - carbonaceous chondrite - amalgamated pellets of protodust from the earliest formation of the solar system Describe kimberlite pipes, how they form, and the importance of the xenoliths they carry in determining the composition of the earth. - formed by high velocity volcanic eruptions - source of volcanic eruptions is very deep in tectonic plate - magma erupts very quickly and explodes out the top of the volcano abruptly - some wood from forests in crustaceous period are also carried up - carry up mantle rocks (xenoliths) and diamonds o xenoliths  xeno = strange; lith = rock Define P and S waves and explain why S waves don’t travel through liquid. - P waves are compressional - S waves cause shearing o S waves can’t go through liquid Describe how seismic waves help us understand the structure of the earth. - generated by earthquakes - speed depends on properties of material the wave is passing through o more dense material = faster speed of waves o less dense material = slower speed of waves - with enough waves passing through at different angles, you can figure out the density structure Explain the origin of Earth’s magnetic field. - generated by convection in the Earth’s liquid outer core - deflects solar winds and keeps the atmosphere intact Lecture 5: TECTONICS THEORY Describe the difference between continental and oceanic crust (approximate thickness and density) and between the lithosphere and asthenosphere (approximate thickness and rigidity). - continental crust o crust: ~ 35 km thick o relatively low density (lighter… 2.65 g/cm3) - oceanic crust o crust: ~10 km thick o higher density (heavier… 3.2 g/cm3) - lithosphere o crust and uppermost mantle o ~ 100-250 km thick o relatively rigid - asthenosphere o upper mantle o around 200 km thick o relative ductile (easily deformed) Explain the basic tectonic model (thin, rigid lithosphere over weak asthenosphere, interacting plates). - lithosphere is thin, cool and hard - asthenosphere is weak and hot - lithosphere broken into large fragments called tectonic plates - plates “float” on the asthenosphere - plates move around and interact with each other Define isostacy and describe how it explains why the oceans are low and the continents are high. - plates “float” at an elevation depending on thickness and density List and explain the evidence for continental drift (fit of the continents, matching rock units, mountain belts, fossils, paleoclimate belts and glaciations). - Fit of the Continents o coastlines of South American and Africa fit together - Matching Rock Units o rock units in South America match rock units in Africa - Matching Mountain Belts o belts of mountain ranges that matched across continents were also same age - Matching Fossils o found fossils of (the same land animal in South America and Africa  land dwelling animal that would not be able to cross water o two continents must have been one land mass at one point to allow these animals to cross freely - Matching Paleoclimate o paleoclimate  types of rocks that were deposited o matched up northern and southern land masses - Matching Glaciations o as glaciers move across the landscape, rocks and other materials get embedded into their bases o as they move, rocks scrape striations into bedrock below  can tell which way the glacier was moving o looking at the glacier movements indicates that the land masses were all attached before Recognize the approximate configuration of Pangea. Describe the evidence from the oceans (topography, heat flow, volcanoes, earthquakes, magnetic stripes) which led to an understanding of sea‐floor spreading. - mid ocean ridges and deep trenches
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