USC need an A – Flashcards
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Difference between atomic mass and atomic number?
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Atomic number is number of protons in nucleus. Atomic mass approximate number of protons and neutrons in nucleus.
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What is a proton and a Neutron?
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Protons carries a postive charge and make the atomic number of an atom. Example Carbons atomic number is 6 so it has 6 protons. Neutrons carry no charge and make up the atomic weight of an atom with protons.
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What is an Isotope and why are the isotopes of some elements unstable?
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Isotopes are variants of an element with different atomic masses this means the element has the same number of protons but different number of neutrons. The reason the elements become unstable is because when there is a significant difference in protons and neutrons it becomes unstable and will break down by radioactive decay.
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Name the four Eons of Earth History and their most important characteristics in terms of the history of continents.
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1. Hadean Eon -Earth's Accretion - Oldest mineral grain - Oldest continental rock 2. Archean Eon - 3900-2500 MA - First crust to the first stable continents - No ocean crust preserved - Vigorous tectonic activity and magnetism - Earliest cratons form - Assembly of early super continents 3. Proterozoic Eon - 2500-450 MA - Stabilization of large continental shields -aggregation of Archean crust into larger units -Extensive reworking of older crust -widely accepted evidence for plate tectonics -Assembly of Columbia - Assembly of Rodinia 4. Phanerozoic Eon - 540-Present MA - Plate tectonic processes comparable to present - Continued continental growth - Formation and breakup of Pangea
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Describe the three main processes of radioactive decay, and the effect they have on the isotope that decays?
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They all change in atomic number and mass. Alpha decay atomic number -2 atomic mass number -4. Beta decay +1 and atomic mass number 0. Electron capture -1 and atomic mass 0.
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Can you name 4 important isotopic systems used for dating, and the materials or minerals that can be dated using these systems?
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C 14 organic material less then 70,000 years old. K-ar (Potassium Argon) Volcanic rocks cooling ages from granite and metamorphic rocks. Rb-Sr (Rubidium-Strontium): igneous and metamorphic rocks U-Pb (Uranium-Lead): best method for granite and very old rocks
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What is meant by the half-life of a radioactive isotope? And how does it affect its use for radiometric dating?: Half-life is the
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Half life is the time required for half the nuclei in a sample to decay. Each radioactive isotope has been constantly decaying since the formation of rocks in which it occurs.
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Why is a study of the early Earth mainly based on evidence from other continents?
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The ocean crust has been recycled many times. Continents are not difficult to observe and continents are better preserved than ocean crust. Also easier to study than deep ocean.
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What is meant by Craton?
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Remnant of Archean continental crust
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What is an Orogen?
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Ancient or present-day mountain belt
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What are the most distinctive characteristics of Archean crust?
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No ocean crust preserved. Made up of granite greenstone terrain, high-grade gneiss terrain. Vigorous tectonic activity and magmetism. Creation of Cratons takes place here.
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Which continents contain Archean cratons?
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Each continent has a craton. A craton is a relatively small area of Archean crust.
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What are the main characteristics of granite greenstone terrain?
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- Found all over the planet - Granite, mostly volcanic, and green rocks - Often has a syncline structure - Silica content increases as it goes from older structure to younger structure
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Where is the oldest crust in North America found? Youngest?
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Oldest: In the Middle The oldest crust is found on the northern half (Archean cratons are welded together by early Proterozoic orogenic belts). Youngest: the edges/Cordillera The youngest is found on the west coast (THE CORDILLERA).
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Describe in a few sentences the overall structure and age relationships in the North American continent:
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Archean cratons (purple) are welded together by early Proterozoic orogenic belts (orange).• Together these make up the Canadian shield Late Proterozoic and Phanerozoic mountain chains have added new material around the old shield• Many of these chains represent an old continental collision• The youngest addition is the Cordillera Much of the North American Cordillera consists of accreted terranes, including continental fragments, island arcs, and accretionary wedges The western margin of North America is being translated northwestward along the San Andreas Fault
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What is meant by supercontinent?
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In geology, a supercontinent is the assembly of most or all of the Earth's continental blocks or cratons to form a single large landmass.
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Can you name two supercontinents, and the approximate time periods when they existed?
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-Rodinia: Formed during the Proterozoic Eon at about 1200 Ma, and broke up by about 1000 Ma -Pangea: Formed during the Phanerozoic Eon at about 280 Ma, and broke up by about 200 Ma
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What is meant by an accretionary wedge? an ophiolite? an island arc? Which if any of these features contribute to continental growth?
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An accretionary wedge is when the material of a subducting plate is scraped off and accredited into a wedge. Usually, it is at the expense of sediments originally found on the continent the subducting plate is subducting into.Continental collision sweeps crustal rock and sediment from the oceans and incorporates them into the continents. Island arc will get pulled up to become a gigantic mountain chain. Builds new continental crust.
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Can you name some other features or processes that result in either growth or modification of continents?
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- Magmatism above subduction zones - Accretion of continental fragments - Lateral translation of continental fragments - Continental collision
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Can you define a normal fault?
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Footwall goes up, hanging wall goes down. Expands the crust rifting.
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What is meant by the strike of a bed?
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It is the orientation of the horizontal line in the plane of the bedding. The compass direction east west north south.
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The difference between a syncline and an anticline?
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Anticline close upwards. The oldest rocks are in the core of the fold. Tip looks like frowny face and looks like an "A". Syncline closes downward. The youngest rocks are in the core of the fold. Looks like "V".
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What is meant by an overturned fold?
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A fold in which the axial plane is tilted and beds may dip in same on both sides of the axial plane.
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A recumbent fold?
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Early horizontal axial surfaces
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What is a dome?
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An up-arced series of strata with beds on all sides dipping away from the center throughout 360 degrees- an eroded surface indicates the rocks become progressively younger away from the center of the structure.
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A basin?
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A down arched series of strata with beds on all sides dipping in towards the center throughout 360 degrees- an eroded surface indicates the rocks become progressively older away from the center of the structure.
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Describe the processes involved in the formation of the solar system and the planets?
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After the formation of the moon the mantle was largely molten. Crust was continuously created and destroyed. Constant asteroid impacts and none of the original ocean crust remains due to the recycle process. Sun 20% less bright. Rich in N2 Co2 and CH4.
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Formation of solar nebula and protostar
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Eagle Nebula: clouds of gas and dust are the birthplace of stars Collapsing cloud: a diffuse, roughly spherical, slowly rotating nebula begins to contract Stars and planetary systems form by collapse of interstellar clouds under gravity Clouds collapse into a disk Central part of disk collapses to form a protostar
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Accretion of planetsimals
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a minute planet; a body that could or did come together with many others under gravitation to form a planet.
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Formation of planets
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Start of nuclear fusion in protostar generates solar wind—strips gas from inner solar system Planetesimals accrete to form terrestrial planets in the inner solar system Gas giants grow around larger planetesimals in outer solar system → These processes started about 4.56 b.y. ago, and took tens of millions of years to complete
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Understand solar nebula, proto-sun, and planetesimal
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Solar nebula- A disk of gas and dust remained to envelop the proto-sun. Proto-sun - a matter from the original nebula concentrated from the collapse of the disks central part (after the cloud collapses into a disk) Planetsimal-km sized grains of rock dust minerals and ices accreted to eventually form terrestrial planets in the solar system.
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Why did the solar nebula collapse into a disk?
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Gravitational forces the central part of disk collapsed to form a protostar. Most likely what caused the solar nebula to collapse was the shock waves from a supernova going off nearby. In either case, gravity gained the upper hand over the Solar nebulas internal pressure and the birth of the solar system began.
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Do you know of a theory that explains the difference between the terrestrial (rocky) planets, and the gas giants, and why these different types of planets occur where they do?
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Planetsimals accrete to form terrestrial rocky planets in the inner solar system. Terrestrial planets: Mercury, Venus, Earth, Mars they were close enough to suns heat that the heat drove off those gases. Different materials condense at different temperatures our solar system formed different types of planets. Gas giants grow around larger planetsimals in outer solar system. Gas giants: Jupiter Saturn Uranus Neptune
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Can you name the terrestrial planets and the gas giants?
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Terrestrial planets: Mercury, Venus, Earth, moon system,Mars. Gas giants: Jupiter Saturn
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How did the moons around the gas giants form, and what are they mainly composed of?
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Titan: Saturn's largest moon; nitrogen atmosphere w/ lakes of methane
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What are the important differences and similarities between Earth and Venus? Do you know of any possible reasons for the differences?
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Venus is often named as Earth's twin because both worlds share a similar size, surface composition and have an atmosphere with a complex weather system. similar size and composition to earth very weak magnetic field no plate tectonics extensive volcanic activity cryptic tectonic structures very thick, hot atmosphere no oceans
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Do you know on what planet the biggest volcano in the Solar System is located, and what sort of volcano it is?:
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Olympus Mons, Mars, Shield Volcano
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What sort of atmospheres do Mars and Venus have, and how do they differ from Earth's?
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Mars: Very thin, cold atmosphere; no surface water at first but actually yes. Venus: Very thick and hot atmospheres. No oceans. Earth: Terrestrial, so it's like oceanic. not cold atmosphere. livable.
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Is there any evidence for liquid water, either past or present, on any of the planets apart from Earth?:
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In Mars, there may have been surface water in the past. Titan has a water mantle.
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What is Titan, and what is remarkable and interesting about it?
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Saturn's Moon Larger than the planet Mercury Rocky core, water mantle, thick ice crust Nitrogen atmosphere, Lakes of methane
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How old is the Earth? Write out a brief history of the formation of the Earth-Moon system
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The EARTH is about 4.5 billion years ago. 1. Initial accretion of the proto-Earth at 4560 Ma. (Early Earth may have had a thick atmosphere, like Venus) 2. Segregation of the core: liquid iron settled to the center of the planet due to its high density 3. Planetary collision and the formation of the Earth-Moon system at about 4500 Ma (Likely loss of early atmosphere) 4. Formation of first crust. About 4.5 billion years ago, Mars-sized body impacted the Earth. The giant impact put a debris into space. Earth reformed as largely molten body... and the Moon aggregated from the debris. The impact sped up earth's rotation and tilted Earth's orbital plane 23 degrees.
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When did the Earth's core form in relation to this history?
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After the formation of the moon, the Earth's mantle may have been largely molten An early crust may have formed, made up of anorthosite: not now preserved Early anorthosite crust on the moon is still there Earth's early crust continuously destroyed and recycled by mantle convection and asteroid impacts
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What was the Earth like shortly after all this happened?
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Heavy bombardment by asteroids and comets during first few hundred million years Rapid convective overturn of mantle continuously recycled the primitive crust Early sun was 20% less bright than at present Early atmosphere rich in N2, CO2 Early oceans hot, acidic No life, and hence no oxygen
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What evidence do we have for the nature and origin of the Earth's early crust?
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An early crust may have formed, made of Anorthosite: not now preserved. Early Anorthosite crust on the Moon is still there. (about 4500 million years old)
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What are the main differences between an impact crater and an impact basin? How large were the objects that produced these features? Do we know what they might have been made of?
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An impact crater is an approximately circular depression in the surface of a planet, moon or other solid body in the Solar System, formed by the hypervelocity impact of a smaller body with the surface. An impact basin is an impact crater that is more than 186 miles (300 km) across. There are over 40 impact basins on the Moon. Asteroids, meteorites or comets are impactors that formed impact craters Many of the early impactors may have been comets, which supplied Earth with water and organic compounds; might have formed Earth's oceans and atmosphere.
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Explain in simple terms the metabolic processes involved in photosynthesis and respiration
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Photosynthesis: Carbon Dioxide + Water → Sugar + Oxygen Respiration: Sugar + Oxygen → Energy + Carbon Dioxide + Water
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What is the organic carbon cycle? What are the main carbon sinks in the organic carbon cycle?
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Carbon dioxide in atmosphere and oceans used by plants to form organic compounds. Carbon accumulates in biomass. Plants may accumulate C to form coal -- fossil C. Plankton in ocean accumulate to form oil and gas. Plants are eaten by animals and metabolized back to carbon dioxide. Burning of biomass: forest fires and forest clearance -- yields carbon dioxide Combustion of coal, oil, and gas for power and transportation, yields carbon dioxide. Biomass, coal, oil and gas are the main carbon sinks.
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What is the inorganic carbon cycle? What are the main carbon sinks in the inorganic carbon cycle?
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Carbon dioxide dissolved in rain reacts with rock to form bicarbonate Ca(HCO3)2 Organisms use dissolved bicarbonate to make shells out of calcite (insoluble) Releases CO2 Shells accumulate to form limestone, made of CaCO2. This is a carbon sink. Subduction carries carbonate rocks into the mantle.The CO2 recycled in subduction-related magmatism Continental collision causes metamorphism and melting in the crust. CO2 released and recycled back into the atmosphere. limestone -- carbon sink
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What is a black smoker, and why is it of interest in discussions of the origin of life?
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It is a geothermal vent that releases iron sulfate (Fe S) Organisms eat irons sulfate and transform it into iron sulfide → Fe SO4 (this becomes their source of energy and helps them building their biomass) It is interesting because it is an example of "extreme metabolism": it does not depend on sunlight and photosynthesis.
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What sort of material might the precursors of life, or the earliest living forms, have been made of?
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self-replicating molecules like RNA�- assembled on solid substrate in shallow water
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What is a stromatolite?
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Is the earliest evidence of life Algal mats build up carbonate mounds in warm shallow seas
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When did the first stromatolites appear in the geologic record?
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3400Ma
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What is banded iron formation, and how do we think it might have formed?
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The oxygen they produced reacted with iron dissolved in seawater, causing iron oxide minerals, such as magnetite and hematite, and silica-rich minerals, such as chert and iron silicates, to precipitate and sink to seafloor. These minerals accumulate in thin, alternating layers of sediments called banded iron formations.
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Outline the stages in the evolution of living organisms, and their approximate timing, as preserved in the geologic record
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Trilobite: 540-280 Ma Extinct arthropods related to horseshoe crabs Bony Fish: appeared about 400 Ma Land Plants: First appeared about 370 Ma Ammonites: 250- 65 Ma Extinct molluscs related to the nautilus Insects: First appeared around 340 Ma Dinosaur footprint: Land animals first appeared at 380 Ma Dinosaurs at 240 Ma Homo Sapiens
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What is meant by the Cambrian radiation?
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An evolutionary radiation of new forms of organism with hard body parts at around 540 Ma
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What are the characteristic features of organisms that lived in the Cambrian as compared to earlier life forms?
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There were land animals. There were flowering plants. There was a huge rise in oxygen. They were oxygen breathers.
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The dip?
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The inclination of the bedding from the horizontal the direction of the dip is perpendicular to the strike and must be specified ( in degrees).
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Strike- slip Fault
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Slip horizontally, parallel to the fault surface. Transform
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Can you name three types of fault rock and explain what they are?
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Fault Breccia- Mechanical process, larger grain size formed from brittle rock. Fault Gouge- chemical process small grain size formed from brittle rock. Mylonite- forms at higher temperatures metamorphic formed from ductile rock.
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Can you name and describe the chemical processes involved in several types of chemical weathering, and several types of physical weathering?
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Chemical: Action of water (hydrolysis [the chemical breakdown of a compound due to reaction with water] of silicates to produce clay minerals), oxygen (oxidation of sulfides to produce sulfuric acid), carbon dioxide (dissolution of soluble elements like K), dissolution by organic and inorganic acids in soil, weathering products (Rock and mineral fragments (detritus)�- Clay (hydrous Al Mg Fe silicates)� - Iron oxides/hydroxides�- Dissolved solids�) Physical: Wedging (frost [A physical weathering process in which the expansion of freezing water in cracks in rock breaks the rock] , roots [ Process by which fractures in rocks are enlarged by the growth of plant roots.], chemical weathering expands joint planes causing them to break, thermal exfoliation [Thermal stress weathering (sometimes called insolation weathering) results from the expansion and contraction of rock, caused by temperature changes.])
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What type of structures are associated with each of them?
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Releasing bends may produce a basin. Restraining bends may produce uplift and mountains.
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What are restraining and releasing bends?
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Releasing bends- A bend to the right on a right slip fault this may produce a basin. Restraining bends- A bend to the left on the right slip faults. May produce uplift mountains.
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How do these different types of faults relate to the different types of plate boundary?
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Tensional tectonics (divergent) produce rift valleys with normal faulting. Reverse faults are most common in convergence zones. Thrust faults are most common in zones of plate convergence. Strike slip faults are particularly common in transform zones.
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Thrust Fault
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A low Angle Reverse fault.
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Reverse fault
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Footwall goes down hanging wall goes up. Shortens the crust. Convergence.
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Can you explain the difference between tensile fractures and shear fractures?
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Tensile fractures open out (glaciers) Shear fractures slip along the fracture surfaces.
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What is the difference between weathering and erosion?
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Weathering: Breaks rock down by physical and chemical processes Erosion: removes rock and weathering products; physical removal of rock and weathering products from the Earth's surface. Erosion is facilitated by weathering. -Agents of erosion: Gravity, wind, running water, waves, glaciers
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Do you know at least relatively which have long and which have short half-lives?
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C: 5730 yrs Rb: 47 billion yrs K: 1.3 billion yrs U-235: .7 billion yrs U-238: 4.4 billion yrs
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What is the difference between chemical weathering and physical weathering?
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Physical weathering is a term used in science that refers to the geological process of rocks breaking apart without changing their chemical composition
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What is the most dangerous type of mass-wasting?
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rock avalanches
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What is a meander?
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a winding curve or bend in a river or road
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How do meanders form, move, and change their geometry? Where is relation to the geometry of a meander would you expect sediment to be eroded, and where deposited?
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Meanders form where there is a slight bend in the river. Position of strongest current shifts from side to side. The position of strongest current pushes outwards at its outside bend, moving and changing the geometry of the river. Erosion at the outside bend. Deposition of point bar at inside bend.
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What is an oxbow lake and how does it form?
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An oxbow lake is a U-shaped body of water that forms when a wide meander from the main stem of a river is cut off, creating a free-standing body of water.
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What controls whether a river has a meandering or a braided geometry?
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How much sediment there is. Huge sediment load, it is braided. If low, meandering.
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What is a delta, and what are the main components of a delta?
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A delta is a low triangular area where a river divides before entering a larger body of water. Delta top- topset beds Distributary channels - channel sands delta front- foreset and bottomset beds.
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What is meant by the base level of a river, and how do temporary base levels form?
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the elevation at which it ends by entering a large standing body of water. They form when rivers cannot easily erode below (i.e. cut down through) layers of resistant rock, or when they encounter bodies of standing water (lakes, reservoirs, and oceans).
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Can you name a common feature found in the western US that results from a change in base level?
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A drainage basin
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What is the longitudinal profile of a river, and in what ways does the river change character along the profile?:
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A cross section of a stream channel along its descending course from the head to the mouth. Its altitude gradually drops. At the upland stream, there is an incised V-shaped valley. At the lowland stream, there is a meandering stream in broad floodplain. At the bottom, there is a delta.
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How do river terraces form?
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Form when land surface is uplifted, causing a stream to erode in its floodplain and establish a new floodplain at a lower level
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What is a levee, and how does it form?
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Built by successive floods, ridges of coarse material that confine the stream within its banks between floods, even when water levels are high.
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Can you name several types of mass wasting, and the relative speed at which the material moves?
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Soil creep -is the gradual down-slope motion of soil under gravity. -Accelerate when wet Slumps -slow slide of water saturated soil -happen on hillsides -More localized Debris Flows -rapid flow of rock fragments in muddy matrix Mudflows -High velocity flow of water saturated mud Rock Falls -free fall of rock -very high velocity -low transport distance (runout) -rock avalanches
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What is meant by mass wasting?
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The large scale motion of rock or soil down slopes under gravity
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Which elements are most likely to go into solution?
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Calcium, Magnesium, Sodium, and Potassium
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What are the main products of weathering?
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Rock and mineral fragments, clay, iron oxides/hydroxides, and dissolved solids
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What percentage of the water on our planet is fresh water, and how much of that exists in the form of groundwater?
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4.04 % is fresh. About 25% is groundwater
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What is meant by water table?
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The water table is the boundary between the zone of aeration and zone of saturation.
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What is groundwater discharge, and how does it affect the position and the flow of rivers?
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Groundwater discharge is where groundwater is discharged into rivers. It can increase the flow of rivers.
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What controls the location and occurrences of springs?
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Aquicludes
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What is an aquifer, and what is the difference between a confined and unconfined aquifer?
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A confined aquifer is in-between two aquicludes. An unconfined aquifer is not in-between two aquicludes.
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What is an artesian well, and what controls the pressure of the water in an artesian well?
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It is a well in which water is under pressure; especially : one in which the water flows to the surface naturally. The pressure is controlled by the aquiclude that confines the aquifer.
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What is groundwater mining?
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Groundwater mining is the removal, or withdrawal, of water in the natural ground over a period time that exceed the recharge rate of the supply aquifer. It is also called "overdraft" or "mining the aquifer"
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Why has the ground surface in the San Joaquin Valley of California subsided so much over the last century?
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Because people have been mining for groundwater in that valley. It creates land subsidence as a result. The water underground gets reduced. The ground surface on top drops in elevation.
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What controls whether a cave is filled with water or air?
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Its position. If it is in the zone of aeration, most likely air. If it is in the zone of saturation, most likely water.
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Why do some rivers disappear underground and then reappear elsewhere?
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Because those rivers are sitting on top of limestone. The limestone is weak. The river can erode an opening and leave at another opening
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What is a sinkhole, and how does it form?
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A sinkhole is a depression or hole in the ground caused by some form of collapse of the surface water. It is a cavity in the ground, especially in limestone bedrock, caused by water erosion and providing a route for surface water to disappear underground
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How do caves in limestone form?
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They form when carbonic acid dissolves limestone
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What is the difference between the porosity and the permeability of rock, and why are they both important?
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Porosity is how much space or holes are in a rock. Permeability is the ability for a rock to allow water to enter it. They are both important because they influence how much water can be in a rock.
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What is meant by the hydrologic cycle, and what part does groundwater play in that cycle?
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The cyclical movement of water from the ocean to the atmosphere by evaporation, to the surface through rain, to streams through runoff and groundwater, and back to the ocean. Groundwater will flow back into the ocean.
