Course Notes - Summary The Good Earth: Introduction to Earth Science PDF

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Summary

Thorough summary of the entire course. Written word for word from instructor and fully summarizes the entire textbook. Chapter 1-8, 11-16

44 pages...

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Chapter 1 Earth Science and the Earth System Earth Science 

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The investigation of interactions among the four components of the Earth System o Atmosphere (air, weather) o Hydrosphere (water, ice) o Biosphere (plants, animals) o Geosphere (land, rocks) … and this interaction with the exosphere (sun, space)

The Scope of (Earth) Science 

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The Earth is a system because of how all of these different components interact with each other o Hydrosphere-Biosphere  Waves destroyed coastal environments  Tourists were swimming, sailing in the ocean o Geosphere-Biosphere  Beaches used by tourists o Geosphere-Hydrosphere  Earthquakes generated tsunami  Waves eroded beaches, deposited sand inland Science is… o A process of discovery that increases our body of knowledge o Information that van be learned; much of it is waiting to be discovered o The curiosity and creativity of scientists in the search for answers to critical questions Science is not… o A list of facts to be memorized How do Earth Scientists Collect Their Data? o Direct measurements  Samples or data are collected at field locations (i.e. rock samples are collected from an outcrop) o Indirect information  Data is collected and then used for interpretation of something else (i.e. measurements of magnetic susceptibility are used to determine rock type present on the ocean floor) o Modeling  Physical of computer models that simulate earth processes (i.e. wave tanks)

Doing Science 

Hutchinson Gas Explosions

Gas explosions in Hutchinson, Kansas, linked to gas storage facility Scientists hypothesized gas traveled to Hutchinson in fractures in underground rock layer A practical example of the use of science to resolve a dangerous situation  Scientific discovery – scientists found additional hazardous gas concentrations  Use of information – geologists used existing knowledge of rocks in region to predict the potential route of gas To “do science” we need observations, a testable hypothesis, and one or more predictions based on the hypothesis o Hypothesis – as testable explanation that can be verified of falsified o Observations – facts, measurements, information, data collected using the senses o Prediction – a statement of what will happen in a given situation or set of circumstances Hypotheses can be tested using either inductive or deductive reasoning o Inductive Reasoning  Drawing general conclusions from specific observations  Involves recognizing patterns in data  Observations that are used to generate a hypothesis  Observation – Hypothesis – Theory o Deductive Reasoning  General principles used to form hypothesis  Involves applying laws and principles  Specific conclusion based on general principle  Hypothesis – Observation – Theory Science follows some basic rules – that loosely define the scientific method o A scientific hypothesis is tentative and can change o A scientific hypothesis should be predictable and testable – test results should either support or falsify the hypothesis o A scientific hypothesis is based on data from empirical (based on experience) observations or experiments o A scientific hypothesis offers a well-defined natural cause to explain a natural event Not all science is “good” science: This can be of particular concern when reading about science reported in the popular media. o “Bad” science. Common pitfalls:  Attacking scientists rather than the science  Common when religious views conflict with science  Misuse of authority  Can happen when politics conflicts science  Confusing cause and effect  If this happened, then that must have been the reason  Poor statistics  Using empirical data incorrectly o o o

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Science and Society 

Earth Scientist’s role in Society o Alert people to earth processes (hazards) that may cause damage or loss of life  Which types of natural hazards are most significant for the region where you live?  Prevention – which hazards are we most likely to be able to prevent?  Example: Prevention of flooding as a result of construction of floodwalls and levees  Adjustment – strategies for minimizing the impact of hazards  Example: Building code regulations in areas of frequent earthquakes o Provide for material needs of society by managing natural resources  Renewable resources – water, soil  Non-renewable resources – oil, coal, metals  Sustainable society – a society that satisfies its need for resources without jeopardizing the needs of future generations o Protect us from activities that may endanger the natural environment  Human-induced air and water pollution can cause long-term harm to ecosystem  Clean-up following the Deepwater Horizon oil spill, Alabama coast o Ensure the future of humanity from global threats such as climate change or an asteroid impact

Chapter 2 Earth in Space Old Ideas, New Ideas 

From a Geocentric to Heliocentric System o Geocentric orbit hypothesis – Ancient civilizations interpreted rising of sun in east and setting in west to indicate the sun (and other planets) revolved around the Earth  Dominant theory for more than 2,000 years o Heliocentric orbit hypothesis – 16th century idea suggested by Copernicus o Confirmed by Galileo’s early 17th century observations of the phases of Venus o Changes in the size and shape of Venus as observed from Earth o Galileo used early telescopes to observe changes in the size and shapes of Venus as it revolved around the sun

Origin of the Universe Earth, a small, rocky planet, orbits the… the sun, a medium sized star, one of billions of stars in the Milky Way galaxy, one of billions of galaxies in the universe 

Size of the Universe: Luminosity o Brightness of pulsating stars – Cepheid variables o Used to determine distance from Earth  Brighter stars – closer to Earth  Dimmer stars – farther from Earth

Repeated measurements determined Cepheid variables were moving away from Earth  Interpretation – the universe is expanding Size of the Universe: Doppler Effect o The apparent change in the frequency of sound waves or light waves due to the motion of a source relative to an observer  Example: change in frequency (pitch) of a siren from passing police car o Example of Doppler Effect  no change in frequency for sound waves when police siren and observer are stationary  Higher frequency when sound waves are compressed for objects moving toward an observer  Lower frequency when sound waves are stretched out for objects moving away from an observer o Doppler Effect: The apparent change in the frequency of sound waves or light waves due to the motion of a source relative to an observer  Sound/light waves are compressed objects moving towards an observer  Sound/light waves are stretched out for objects moving away from an observer o The change in frequency of a passing siren can be used to determine the speed of the police car o Light on Earth is a form of solar radiation and occurs at specific wavelengths from 380-750 nanometers  The color of light from distant stars is stretched (“shifted”) toward wavelengths at the red end of the spectrum o Astronomers use the degree of red shift to determine the distance to far away galaxies  More than 13 billion light years (distance) from Earth Size and Age of the Universe o If the color of light from other stars is “shifted” toward the red end of the spectrum  Other objects in the universe are moving away from Earth and from each other  The farther away the star, the greater the red shift and the faster the star is moving away from us  The universe must be expanding  Light from the most distant stars has traveled more than 13 billion light years (distance) in 13 billion years (time) The Big Bang Theory o Reversing the expansion of the universe suggests the universe began with an episode of rapid expansion from a much more compact form o The almost instantaneous period of rapid expansion is known as the Big Bang o Within hours of the Big Bang, simple elements (hydrogen, helium) formed as subatomic particles combined  Hydrogen – 1 proton + 1 electron  Helium – 2 protons + 2 electrons + 2 neutrons o

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Stars and Planets 

Just 3 elements – hydrogen, oxygen, carbon – make up 90% of the human body (by weight)

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o Five more – nitrogen, calcium, phosphorus, potassium, sulfur – make up 9% more o Small amounts of many other elements needed for life Hydrogen formed soon after the Big Bang Other elements and complex compounds formed during the life cycle of stars Gravity pulled together irregular clouds of gas and dust generated from the Big Bang to form galaxies (systems of stars) Gas and dust material clumped together to form millions of stars (ongoing process) o Very high temperatures and pressures in the interiors of starts fuses hydrogen atoms together – nuclear fusion – to form helium o Stars burn out when hydrogen is used up Stars vary in size and age o Giant stars are 100-1,000 brighter than the sun but burn out faster o Giant stars burn out in 10-20 million years o Intermediate-sized stars such as the sun will last approximately 10 billion years The sun will collapse when hydrogen is used up o Resulting in a temporary temperature rise and expansion (to form a giant red star) o Higher temperatures would fuel more fusion converting helium to carbon Giant stars collapse over multiple stages, initially forming red supergiant stars o Collapse forms increasingly complex elements (e.g. carbon to oxygen) Final stage is a massive explosion – supernova – that fuses heavier elements together and blasts them through the universe When stars form they are surrounded by a rotating disk of cosmic debris Gravity pulls debris together to form planets that revolved in a consistent direction around a star o Heavier, rocky planets closer to star o Lighter, gas-rich planets farther from star Potentially thousands or millions of extra-solar planets revolved around other stars

Our Solar System   

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Solar system – sun and surrounding planets Sun = 99.8% of total mass of the solar system o Sun is 150,000,000 km from Earth Sun undergoes differential rotation o Sun’s equatorial region rotates faster (25 days) than polar regions (36 days) o Results in disruption of sun’s magnetic field to produce sunspots and solar flares Sunspot cycle o Variation in the number of sunspots over an 11-year cycle o Few sunspots visible during solar minimum o More than 100 sunspots during solar maximum The solar wind is a stream of charged particles emitted from sun’s magnetic field (1,600,000 km/hr) The solar wind affects a volume of space known as the heliosphere Earth’s magnetic field deflects the solar wind Interactions of solar wind with Earth’s magnetic field generates aurora in the upper atmosphere of polar regions

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Occasional solar eruptions can disrupt Earth’s magnetic field to produce electrical blackouts o Satellites in greater danger from solar flares than features on surface Eight Planets o 4 terrestrial planets (Mercury, Venus, Earth, Mars) o Jovian planets (Jupiter, Saturn, Uranus, Neptune) What about Pluto? o Improved technology resulted in recent discoveries of several distant objects that were similar size or larger than Pluto o International Astronomical Union (IAU) could either…  1. Consider the new objects as new planets  2. Classify the new objects – and Pluto – as a new group of objects o IAU chose option #2 o IAU adopted a new definition of the term planet  A planet is an object that orbits a star and is massive enough (~400 km radius) for gravity to pull its material into an approximately spherical shape. A planet would have cleared the neighborhood around its orbit o Pluto does not meet the last part of the definition and was considered a founding member of a new class of objects – dwarf planets Terrestrial Planets o Composed of rocks o Divided into compositional layers  Crust – composed of lighter elements (e.g. silicon, oxygen)  Mantle  Core – composed of heavier elements (e.g. iron, nickel) found in metallic meteorites Jovian Planets o Large, gas planets o Much of the volume of the planets is a thick atmosphere overlying ocean of liquid gases o Characterized by many moons and ring systems

Earth, the Sun, and the Seasons 

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Why is it colder in winter and warmer in summer? o Common misconception that Earth is closer to the sun during summer and farther away in summer o But Earth is actually closer to sun in winter (in the northern hemisphere) and farther away in summer o Seasonal temperature contrasts are due to the tilt of Earth’s axis and angle of Sun’s rays  Tilt=23.5 degrees Amount of solar energy (insolation) reaching Earth’s surface depends on the angle the Sun’s rays strike Earth More heat delivered by insolation where the Sun is directly overhead o As sunlight is distributed over a smaller area o Total annual insolation is least at Poles, greatest at the Equator o Solar energy is diluted over a larger area when sunlight strikes at a low angle

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Sun is directly overhead at different places (tropics, equator) during different seasons o During summer in the northern hemisphere, the sun is directly overhead at the Tropic of Cancer o During winter in the northern hemisphere, the Sun is directly overhead at the Tropic of Capricorn in the southern hemisphere Sun is directly overhead at different places (tropics, equator) during different seasons o During spring and fall in the northern hemisphere, the sun is directly overhead at the Equator Why day length changes? o Hours of daylight change  With latitude – higher latitudes have more daylight than low latitudes in summer, less in winter  With time of year – all locations have more daylight in summer and less in winter

The Unique Composition of Earth 

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Earth’s interior can be divided into three major compositional layers o Crust – composed of lighter elements (e.g. silicon, oxygen) o Mantle – composed of rocks made up of 3 key elements (oxygen, silicon, magnesium) o Core – iron and nickel  Solid inner core  Partially melted outer core is source of Earth’s magnetic field Scientists recognize two layers with different properties near the surface o Lithosphere – rigid outer layer composed of crust and upper mantle o Asthenosphere – plastic, slowly flowing layer in uppermost part of mantle Lithosphere divided into large slabs known as tectonic plates o Plates move over Earth’s surface to produce earthquakes, volcanoes, mountain belts, and various feature on the seafloor Geothermal gradient o Earth’s temperature increases with depth  Average temperature rise is 25 degrees/km o Heat generated by the:  Formation of the planet – all terrestrial planets cooled following formation  Only large planets still retain heat  Radioactive decay of elements in Earth’s interior Earth shares many features with other planets, so what makes it so special? o Liquid water o Gravity and protective atmosphere o Life-sustaining gases o A strong magnetic field Liquid water is essential for life on Earth and is maintained by appropriate temperature range (0-100 C) o Venus  Too close to sun, original water evaporated to atmosphere

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Water vapor molecules (H2O) split by ultraviolet radiation and hydrogen lost to space

Mars  Too cold today to have liquid water, some frozen Earth’s size is sufficient to produce enough gravity to hold a thick atmosphere of gases in place o Atmosphere protects us from:  Incoming asteroids/comets  Harmful solar radiation (x-rays, UV) o Earth’s biosphere has altered the composition of the atmosphere to add oxygen and extract toxic carbon dioxide o Atmosphere composition affects temperature  Higher carbon dioxide content on Venus produces temperatures of 464 C o Composition of Earth’s atmosphere just right to absorb enough heat to keep average temperature of 15 C o Greenhouse Effect  Water vapor, carbon dioxide (0.038%) gases absorb heat  Without greenhouse effect, temperatures would be -18 C Earth’s magnetic field protects Earth from harmful solar wind that would strip away atmosphere o Magnetic field due to molten rocks in the outer core and relatively rapid planetary rotation:  Smaller planets or slowly rotation planets have lost heat and have weak magnetic fields o

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Chapter 3 Near-Earth Objects Chevy Asteroid    

1992: A football-sized meteorite crashed through the trunk of Michelle Knapp’s Chevrolet Malibu Classic in Peekskill, New York Near-Earth objects o NEOs are asteroids or comets that approach Earth Earth carries the scars of past impacts with asteroids and comets A devastating collision with a 10 km wide asteroid is hypothesized to have caused a global extinction event 65 million years ago

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Most NEOs do not come close to Earth but occasionally one may approach within the moon’s orbit o In 2029, the asteroid Apophis is expected to come within 36,000 km of Earth Few asteroids were recognized in the inner solar system 100 years ago. Today, more than 90,000 asteroids have been identified Asteroids o Size – space pebbles to 940 km in diameter (Ceres) o Travel at ~ 16 km/s (36,000 mph) o Composed of rock and/or metals

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Meteor – asteroids that burn in atmosphere Meteorite – an asteroid that strikes Earth’s surface

Comets o Size – generally larger than asteroids  Many are 100s of km across o Travel faster than asteroids  ~50 km/s (112,000 mph) o Composed of dust and ice with a rocky core  “Icy dirtballs” o Analysis of light from explosion on Tempel 1 revealed information on comet composition o Common compounds present including  Cyanide  Carbon dioxide  Water – scientists are investigating if comets could have supplied water in Earth’s early oceans o 1908 explosion of a comet in the atmosphere over Tunguska, Russia, destroyed forest over an area the size of a major city (2,100 km^2) Two types of comets o Short-period comets  Orbit the sun with similar paths to outer planets in solar system  Originate in Kuiper Belt beyond Neptune  Return to inner solar system every few years o Long-period comets  Travel toward the sun with irregular orbits that may be at a high angle to planets  Originate in the Oort Cloud at the outer limits of the heliosphere  Return to inner solar system over decades to thousands of years

Impact Features 

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NEO collisions with rocky planets and moons form 2 types of impact craters o Simple craters o Complex craters Craters all feature o Broken rocks (breccia) o Ejecta thrown from crater o Melt rocks o Altered minerals Simple Craters o Bowl-shaped o Few kilometers wide o Eject blanket of material surrounding the crater Complex craters o More than 4 km wide o Central peak,

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o ring structures around edge of crater o Ejecta blanket surrounding crater Crater vs NEO size o An impact crater is 10-20 times larger than the colliding NEO o Example: Manicouagan Crater, Canada  ~100 km wide crater  NEO was 5-10 km in diameter Craters on Earth o More than 150 impact craters identified on continents o Few impact sites identified in oceans

Impact Hazards 

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The impact of a NEO with a diameter equivalent to… o Lincoln Memorial (~50 m) would destroy a large city o National Mall (~1 km) collides with Earth every 100,000 years and would devastate most nations o Washington, D.C. (~10 km) collides with Earth every 100 million years and would produce global-scale destruction Large NEO impacts are infrequent o Impacts of relatively...