Midterm 1 Review Questions.docx

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University of Toronto Mississauga
Earth Science
Lindsay Schoenbohm

Midterm Review Sheet Lecture 2 : Formation and Structure of earth 1. Describe formation of solar system including sun and orbiting planets • Anebula forms from hydrogen, helium and helium left over from big bang Nebula condenses into a swirling disc, with a central ball surrounded by rings Ball at centre grows dense and hot enough for fusion → becomes the sun In the rings, dust particles collide and stick together, forming planetesimals Planetesimals grow into the proto-Earth; interior heats up and becomes soft Gravity reshapes proto-Earth into a sphere; interior differentiates into a core and mantle Soon after Earth forms, a small planet collides with it → blasts debris forming a ring around Earth The moon forms from the ring of debris Atmosphere develops from volcanic gases; when the Earth becomes cool enough, moisture condenses and rains to create the oceans. Some gases may be added by passing comets • Planetsimals use gravity to pull in nearby objects incorporating debris within making it a full fledged planet 2. Explain process which shaped earth into interlay layered sphere • Transform kinetic energy into thermal energy during collision, decay of radioactive elements, bombarded by meteorites • Iron alloy separate and sink to centre (creating core) and rocky materials remain in shell surrounding centre (crust) 3. Explain how moon formed • Small planet collides with earth – creating debris around earth  this debris forms moon 4. Describe basic composition and thickness of major layers of earth : crust, mantle, inner core and outer core • Crust : oceanic, continental and oxygen – 10-70 km • Mantle: peridotite, soft enough mantle rock – 2880 km • Outer core: liquid iron alloy – 2260 km • Inner core: solid iron nickel alloy – 1220 km 5. List and explain 5 methods used to understand structure and composition of earth’s interior Experiments that mimic core conditions Computer models Meterorites  get sample of all materials that makes up earth, composition to explain own planet Kimberlite pipes  Seismic waves (p and s waves) generated by earthquakes, when rocks break creates vibrational energy = speed depends on density of material (different types of waves that interact w/ material in different ways) 6. Know age of earth and how it is determined from rocks, minerals, meteorites Midterm Review Sheet • 4.5 billion years • Samples  to date how old the earth is • Stony creek 4.03 billion 7. Define p and s waves and why s waves don’t travel thru liquid PWaves: causes particles of material to move back and forth parallel to direction in which wave itself moves S Waves: causes particle of material to move back and forth perpendicular to direction in which wave itself moves  s waves don’t travel thru liquid (particles in liquids aren’t close enough to support movement of particles moving perpendicular to direction wave is moving) 8. Explain why seismic lines take curved rather than straight path thru earth Vibrations  not straight Changes in density as the lines move throughout the earth 9. Explain origin of earth’s magnetic field Convection is transfer of heat thru fluid Outer core spins around inner core Convection and polarity New rocks form at mid ocean ridges which causes reverse polarity Lecture 3: Tectonics I 10. describe difference b/w continental and oceanic crust (approximate thickness and density) and between the lithosphere and asthenosphere • continental(35 km thick )is thicker than oceanic (10 km thick) • density: ocean is more dense (3.2 g/cm^3) vs continental crust (2.65) • lithosphere(100-250km ) on top what we on right now, asthenosphere(200km) is below lithosphere . lithos is rockier (rigid) . asthenosphere is ductile (easily deformed) 11. explain the basic tectonic model (thin, rigid lithosphere over weak asthenosphere, interacting plates) lithosphere = thin , cool, weak, asthenosphere = hot and weak. Lithosphere broken up into large fragments into plates  plates float on asthenosphere – plates moves around and interact with other 12. define isostacy and describe how it explains why oceans are below sea level and the continents are , for the most part, above sea level Isostacy plates float on elevation depending on thickness and density Continental (LOW DENSITY) so higher elevation since Ocean (HIGHER density) Midterm Review Sheet 13. list and explain the evidence for continental drift (fit for continents, matching rock units, mountain belts, fossils, paleoclimate belts and glaciations) • fit for continents – how southAmerica andAfrica fit together • matching rock units – fit of continental shelf (rocks adjacent are similar together) • matching mountain belts – mountain formations of northAmerica andAfrica have same structure • matching fossils – fossils remains of land animals that have migrated to continents before land split • matcing paleoclimate belts – different environments stitched together (similar climates) • matching glaciations – gigantic ice sheet traveling away from the center )stritations and tills) 14. recognize approximate configuration of pangea WHAT IT LOOKS LIKES  200 million years ago • created theory of continental drift 15. describe evidence from oceans (topography, heat flow, volcanoes, earthquakes) which led to an understanding of sea floor spreading sea floor spreading process (mid ocean ridge which spread the continents): created by magnetic reversals a. heat flow (divergent floors move away to allow lava to seep through) b. volcanoes form on the island that line up with the trenches c. earthquakes form thru heat flow + underwater mountain ranges 16. explain formation of magnetic stripes on sea floor there is an alternating normal and reversed polarity in rock layers new rocks being formed, which spreads out the old rock and old new old new  reverse polarity 17. describe evolution of sea floor from ridge to subduction zone in terms of age of ocean crust, it’s depth below sea level, its magnetic signal (normal or reverse) and amount of sediment cover subduction zones: when plate tectonics move under another plate tectonic and sink into mantle as the plates converge. Evolution of sea floor from ridge to subduction zone is at mid oceanic ridges where new oceanic crust is formed thru volcanic activity: stripes of rock parallel to crest alternate in magnetism(normal reverse normal,etc). rocks away from ridges are older and sediment is thicker, rocks near ridges are younger and sediment is thinner 18. explain why deep earthquakes occur at subduction zones Midterm Review Sheet friction causes the plates to lock in position until the stress exceeds the shear strength of fault zone. This accumulation of stress causes deformation in rock mass around the lock fault, which is suddenly released when the fault slips 19. explain why continental crust cannot be subducted continental is less dense than oceanic crust which causes oceanic to subduct Lecture 4: Tectonics II 1. Name and define 3 types of plate boundaries a. Divergent : moving away from each other, 2 oceanic plate move apart by process of sea floor spreading, new oceanic lithosphere forms, takes place at mid-ocean ridges b. Convergent: moving towards each other, 2 plates move towards one another, one plate sinks down while the other rises. Oceanic lithosphere has to sink down and continent or oceanic lithosphere can rise up c. Transform: moving past each other 2. Recognize different types of plate boundaries (e.g. transform/continent-continent or convergent/ocean-continent, etc) from distribution of earthquakes, volcanoes, topography, and age of ocean floor Topography – result of plate tectonic movement (mid ocean ridges, deep ocean trenches, and fraction zones) 3. Explain some of the different features found at ocean-ocean, ocean-continent and continent- continent convergent zones (trench, volcanic arc, mountain range). Given a real world example of each. Converge Ocean – ocean : shallow waters around land mass, dense earthquake activity, thin belt of volcanic activity Ocean – continent: high elevation on land, low depth in waters, dense earthquake activity, thin belt of volcanic activity, young oceanic crust Continent – continent: wide belt of high elevations along plate, some instances of low sea levels, randomly sparsed patter of earthquake activity , low instances of volcanic activity 4. Describe the evolution of a divergent boundary from initial continent rifting to mid ocean ridge. Know a real world example of a continental rift Evolution of a divergent boundary • Rifting causes the continent to crack and break apart; new mid­ocean ridge  forms and sea­floor spreading begins • As continents pull apart, magma rises from the mantle into a magma  chamber • Some magma along the sides of the magma chamber cools to form gabbro o Gabbro moves away  Midterm Review Sheet from the magma chamber o New magma rises to keep volume of magma constant • Some magma rises to fill  vertical cracks above the magma chamber, solidifying to form dikes o Dikes break in half as sea­floor spreading  continues and move to the side o New magma rises to fill the crack and create new dikes  • Some magma makes  it to the surface and extrudes as basalt pillows → forms the top of the sea­floor crust Divergent can be ocean­ ocean (mid Atlantic ridge), this is very common because of the mechanism of convection or continent­continent  (African rift valley) this is uncommon because it will become ocean­ocean soon after. Divergent ocean­ocean  boundaries are not linear because as rifting progresses spreading ridges form perpendicular and transform faults  form parallel to plate motion. 5. Describe and be able to draw the basic structure of oceanic crust (magma chamber, sheeted dykes, pillow basalts, sediments) 6. Describe some of the features associated with a continental transform fault and give a real world example • No new plates form and no plate is consumed, earthquakes occur on segment of a fracture zone that lies between the 2 ridge segments, very young oceanic crust(closer to ridge) • NorthAmerican - pacific 7. Explain origin of hot spots, how they tell us about plate motion Heat source for hot spots = results of mantle plume: very hot rock rising up through the mantle to base of lithosphere 8. Know approx. speed of tectonic plates Divergent: 1-10 cm / year 9. Describe 3 driving mechanism of plate tectonics (ridge push, slab pull, and mantle convection) and know the relative importance of each. • Mantle Convection: when mantle rocks near radioactive core are heated – become less dense than cooler upper mantle rocks  warmer rocks rise while cooler rocks sink – creating verticle currents within mantle. Movement cerates pockets of circulation within mantle called convection cells. Circulation of these convection cells could be driving force behind movement of tectonic plates over asthenosphere. Certain areas in mantle are hotter and less dense, so materials in mantle move up and cool down – eventually sink to only heat up again  process will carry other things with it – can drag to lithosphere, slow moving convection currents, take lithosphere with it • Ridge-Push Force: ridge push is a gravitation force that causes a plate to move away from crest of an ocean ridge, and into a subduction zone • Slab Pull Force: result of plate subducting at steep angle thru the mantle; this downward motion tends to pull other side of the plate away from ridge crest Midterm Review Sheet Lecture 5 Minerals I 1. Describe structure of an atom (nucleus with protons and neutrons, electron cloud) Composed of electron cloud made of negatively charged electrons + a nucleus  nucleus has same # of positive and neutral neurons, outer shell has about same # of negative electrons 2. Define an element Grouping of same atoms that all have same # of protons and neutrons, a pure substance that cannot be separated into other elements 3. Define fundamental properties of a mineral (naturally occurring, orderly internal arrangement/crystal structure, definable chemical composition, inorganic) • Naturally occurring : produced in nature • Solid : can maintain its shape indefinitely • Crystalline structure: orderly internal arrangement; fixed • Definable chemical composition: possible to write chemical formula • Inorganic: sugar and protein are not minerals 4. Know difference between cleavage and crystal form • Crystal form = shape of crystal, crystal face = singular surface • Cleavage = tendency to crystal to split along definite structural planes o Forms in direction where bonds holding atoms together in crystal are the weakest o Cleavage planes can be repeated 5. Know how the moh’s hardness scale works, relative hardness of a few key minerals (e.g. talc, calcite, quartz, diamond) Mohs Scale Mineral 1 Talc 2 Gypsum 3 Calcite 4 Fluorite 5 Apatite 6 Feldspar 7 Quartz 8 Topaz 9 Corundum Midterm Review Sheet 10 (hardest) Diamond 6. Understand how to identify other basic properties of minerals such as colour, luster, and streak Colour, bad diagnostic test Luster – the way a mineral surface scatters light, can be metallic or non-metallic Texture- how mineral feels to the touch. Hardness – ability to resist scratching, Mohs scale Cleavage-how a mineral breaks Fracture- splitting with no orientation Density- how dense a mineral is. Streak – rubbing the mineral against a porcelain plate Special properties – magnetism, salty, density, reaction with acids 7. Describe difference covalent and ionic bonds Covalent: 2 non metals , shares electrons (e.g. water  2 hydrogen) Ionic: strong, metal and non metal (e.g. salt  sodium (metal) – chloride (non metal)  transfers electrons 8. Relate properties of halite to its mineral structure Halite – 3 cleavage planes, salty, symmetrical, 90 degrees 9. Compare crystal structure of diamond and graphite and relate structure to mineral properties Diamond: covalent : silicatetrahedra Graphite : hexagonal prism Diamond and graphite have the same chemical composition – pure carbon but have different structure Lecture 6: Minerals II 10. Relate properties of quartz to its mineral structure 11. Be able to draw and explain structure of silia tetrahedron Midterm Review Sheet 12. Name 3 most abundant elements in whole earth and 3 most abundance elements in earth’s crust Whole earth : iron, oxygen, magnesium Earth’s Crust: oxygen, silicon, aluminum 13. Describe arrangement silica tetraherea in quartz, feldspar, mica, amphibole/hornblende, pyroxene, and olivine. Know how mineral structure and composition relate to physical properties such as crystal shape and cleavage 14. Place olivine, pyroxene, amphibole, biotite, quartz, muscovite, potassium feldspar and plagioclase feldspar in correct places in bowen’s reaction series Bowen’s reaction series: sequence in which minerals form during a cooling of a melt 15. Describe different minerals found in continental and oceanic crust and the mantle, and how the density and silicate content varies Mantle – mafic (rich in Mg and Fe) Ocean Crust – intermediate Continental Crust – silicic(no Mg and Fe) • More iron and magnesium • Pyroxene
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