• Earth Science Mid Term topics outline

    • Topic I - prologue
      • Observations and inferences
      • Classification
      • Density = Mass/Volume  (g/ml or g/cubic cm)
        • Less dense rises, more dense sinks
        • Size and shape DOES NOT AFFECT DENSITY
        • If temperature increases, density decreases (indirect)
          • WATER IS THE EXCEPTION (LESS DENSE AS A SOLID)
        • If mass and volume increase together, density stays the same
        • If pressure increases, density increases
      • Rate of change
        • Steep slope = great change
        • gentle slope = little change
      • GRAPHING very important to know relationships between x and y
        • direct, both x and y increase or both x and y decrease
        • indirect x increases and y decreases, or x decreases and y increases
        • cyclic  predictable change 
    • Topic II:  MEASURING THE EARTH (ESRT page 1,2,3, 14,)
    • Evidence of earth's shape
          • Oblate spheroid
            • Equatorial diameter > polar diameter
          • Altitude of polaris is equal to observers latitude in Northern hemisphere only 
          • Ships passing over horizon
          • Pointer stars in big dipper point to polaris (end of handle of little dipper
          • Change in weight from the equator (less, farther from center of the earth) to the poles (more, closer to the center of the earth
    • Structure of the earth
          • Lithosphere 
          • Hydrosphere
          • Atmosphere:  Be familiar with temperature, altitude, pressure, and water vapor for each layer and location of ozone
            • Chemical composition of each layer
    • Positions of the earth
      • Coordinate system
        • Latitude measures north or south of the equator (parallel lines circle the globe)
        • Longitude measures east or west of the Prime Meridian (semi circles run pole to pole)
          • Solar time (local time) and Solar noon (Greenwich Mean Time)
          • Rate of rotation is 15 degrees per hour (time zones)
            • time earlier than GMT longitude is west  of local time
            • time is later than GMT longitude is east of local time
        • NY State latitude and longitude 
      • Fields
        • Isolines
          • Isobars = pressure
          • isotherms = temperature
          • contour lines = elevation
        • Gradient or slope 
        • Contour interval is the elevation between two contour lines
        • index counter is darker labeled counter line
        • Hachure lines indicate a depression (dip in the land)
        • Contour lines bend upstream as they pass a river/stream
        • benchmarks exact elevation
        • map scale  (graphic scale -see ESRT pg 2)
        • Profiles (side view)
        • Maximum possible elevation  and minimum possible elevation

     

    • TOPIC 3:  EARTH IN THE UNIVERSE (ESRT page 1, 15
      • Our solar system
        • The Earth is a planet which revolves around the Sun.  The Moon is a satellite that revolves around the Earth.  The Sun is a star. The planets and their moons, as well as the asteroids between the planets, revolving around our Sun.
        • Our Solar System is one of billions within our galaxy, The Milky Way.  The Milky Way is one of billions of galaxies in the universe. 
        • The Solar System is about 4.5 billion years old.  Individual planetary characteristics are in the Reference Tables.
      • The Big Bang Theory is the most widely accepted theory for the creation of the universe.  
        • all matter and energy started out concentrated in a small area and approximately 15 billion years ago it exploded.
        • Evidence for the Big Bang includes the fact that galaxies are moving away from us and each other.
        • The Doppler Effect is the shifting of wavelengths in a  spectrum due to an object moving toward or away from the observer.
          • If the object is moving toward the observer, the electromagnetic waves are bunched together resulting in a blue shift. 
          • If the object is moving away from the observer, the electromagnetic waves are spread out resulting in a red shift.
      • The Milky Way galaxy is about 100,000 light years across and has a spiral shape.  We are located towards the end of a spiral arm.
        • A light year is the distance light travels in one year 
      • The Sun is an average star (part of the Main Sequence) and is about half-way through its life cycle.  It gets its energy from nuclear fusion reactions in which light elements (hydrogen) combine to form heavier elements (helium), giving off tremendous amounts of energy
        •  Luminosity refers to a star’s brightness, compared to the Sun, if it were the same distance as the Sun.  Generally, hotter stars have a color toward the blue end of the spectrum and a greater luminosity 
      • Stars are formed in gas and dust clouds (nebulae) and go through stages, depending mostly on their mass.  
        • They start out as a main sequence star, then into either a red giant or a supergiant, depending on the mass.  
        • A red giant may then collapse into a white dwarf and then a black dwarf (dead star).  A supergiant could explode into a supernova and become either a neutron star or a black hole. 
      •  A geocentric model of the solar system has the Earth at the center, with planets, moon, and sun revolving around it in circular orbits  (this was the first model of the solar system)
      •  A heliocentric model of the solar system has the Sun at the center, with planets moving around it, and the moon moving around the Earth, all in circular orbits, and the stars stay in one place
      •  The heliocentric model was improved by Kepler’s elliptical orbits, which explained why celestial objects appear to change in size (apparent diameter).....because our distance from them changes (objects that are closer appear to be bigger)
      • KEPLER’S LAWS
        • The eccentricity of an ellipse (elliptical orbit) can be determined by dividing the distance between foci by the length of the major (longest) axis of the ellipse.  It is always a value between zero and 1.0.  
        • [eccentricity is how “flat” a circle is, therefore, if the eccentricity value is close to zero, it’s close to a perfect circle; if the value is close to 1.0, it is very “flat” or “eccentric”]
      •  The Earth’s orbit is a slightly eccentric ellipse
      • Because it is elliptical, sometimes the Earth is closer to the Sun (January) so it travels faster and the Sun appears larger.  When it is farther from the Sun (June) it travels slower and the Sun appears smaller.
      • Gravitational force between two objects depends on the masses of the objects and the distance between them.   
        • Distance and force have an inverse relationship:  as distance between objects increases, force between them decreases.
        • Therefore, when a planet is closest to the Sun, its speed is greater, force of attraction is greater, kinetic energy is greater

     

    • TOPIC 4:  EARTH MOTIONS
      • The apparent daily motions of the stars, moon, sun, and planets are due to the Earth’s rotation 
        • All celestial objects move generally from east to west at approximately 15o per hour (the rate of Earths rotation)
        • Rotation:  spinning on an axis
        •  Revolution:  orbiting around an object
        • [if you get confused, look up the Solar System Data Table in the Reference Tables -- when you see that the Earth’s period of rotation is 24 hours, you will realize that a “day” is caused by spinning; when you see that the Earth’s period of revolution is 365 days, you will realize that a “year” is caused by orbiting the Sun]
      •  THE MOON
        • The moons orbit is inclined (tilted) relative to the plane of earths orbit
        •  Solar eclipses occur at New Moon and are seen during the day;  
        • Lunar eclipses occur at Full Moon and are seen at night
        • The moon revolves once around the Earth in 27.3 days.  It also rotates once on its axis in 27.3 days.  This is why we always see the same side of the moon [periods of rotation and revolution are equal]
        •  In the time it takes the moon to make one revolution around the Earth, the Earth has also moved around the Sun, so it takes the moon a little while longer to “catch up” to the Earth and be in the same phase again -- the moon’s cycle of phases takes 29.5 days
        • The phases of the moon are caused by the moon’s revolution around the Earth
        • Tides are caused by the Moon’s gravitational pull on the Earth.  
          • There are two high tides and two low tides every day (each is about 6 hours apart).  When the Moon is New or Full, the Sun and Moon are pulling together resulting in extreme tides called Spring Tides.  When the Moon and the Sun are at right angles to the Earth during the Quarter phases, the result is moderate tides which are called Neap Tides.   
      • EARTH’S REVOLUTION AND SEASONS
        •  The seasons on the Earth are caused by:
        • 1. the Earth’s revolution around the Sun
        • 2. the tilt of the Earth’s axis  [if the Earth were not tilted, we would have no seasons because no time of the year would receive more sunlight than another;  if the Earth were tilted more, we would have a larger difference in the amount of sunlight received so winters would be colder and summers would be hotter]
        • 3. the parallelism of the Earth’s axis (the North pole always points to Polaris)
        • The Earth is tilted 23.5o from the plane of its orbit; therefore, the Sun’s direct rays hit the Northern hemisphere when the Earth is tilted toward the Sun, and they hit the Southern hemisphere when it’s tilted away.  When it’s tilted neither toward or away from the Sun, the Sun’s direct rays strike the equator.
        • In the northern hemisphere, the noon Sun is always due south
        • In summer in the Northern hemisphere (June 21), the Sun appears to rise north of east and set north of west.  This causes a longer arc (path) in the sky producing our longest period of daylight and the time when the noon Sun reaches its highest point (altitude) in the sky.  The suns direct rays are at the tropic of cancer 23.5 N. The North pole has 24 hours of daylight on this date.
        •  In winter in the Northern hemisphere (December 21), the Sun appears to rise a little south of east and set a little south of west.  This causes a shorter arc (path) in the sky producing our shortest period of daylight and the time when the noon Sun reaches its lowest point (altitude) in the sky. The suns direct rays are at the Tropic of Capricorn 23.5S The North pole has 24 hours of darkness on this date.  
        • Equinox:  March 21 and September 23  -- when neither pole is tilted toward the Sun,  every place on Earth has 12 hours daylight and 12 hours darkness  and the direct rays are at the equator (think of equal days on the equinox)
        •  Zenith:  the point directly overhead (90o angle)   [remember:  the Sun can never be directly overhead anywhere beyond the tropics (23½o north or south of equator)]
        • The Earth is actually closer to the Sun in January (perihelion) and farther from the Sun in July (aphelion)
      •  TERRESTRIAL OBSERVATIONS
        • Earth’s rotation is slightly greater at the equator (more distance to cover in the same amount of time)
      • Evidence of the Earth’s rotation:
        • 1. foucault pendulum -- although the pendulum appears to be changing direction, it is actually swinging in the same direction but the Earth is rotating under it
        • 2. coriolis effect -- fluids (winds) appear to be deflected to their right in the northern hemisphere.  Keep in mind that the object is deflected to the right of its intended path, not your right! And deflected to the Left in the southern hemisphere
    • TOPIC 5:  ENERGY IN EARTH PROCESSES
      • Electromagnetic energy is radiated (given off) by all objects -- generally, the higher the temperature, the more energy radiated 
      • The different types of electromagnetic energy from the Sun make up the “electromagnetic spectrum”  
      •   At a temperature of absolute zero (-273oC or 0o Kelvin), an object would radiate no energy, but this temperature is a theory -- it has never been reached
      •  Wavelength:  the distance between crests of a wave
      • Electromagnetic energy waves travel at the speed of light 
      •  Infrared energy:  heat 
      •  When electromagnetic waves come in contact with something, they can be:
        • refracted  (bent as they pass through)
        • reflected  (bounced back)
        • scattered  (dispersed in several directions)
        • absorbed  (kept inside the object)
        • transmitted  (pass through completely unaffected)
          • [the type of energy (wavelength) and the type of material the energy encounters determine what will happen.  For instance, visible light at a short wavelength can be transmitted through clouds unaffected, but infrared (heat) energy at a longer wavelength will get absorbed by a cloud.]
      • GREENHOUSE EFFECT
        •  The greenhouse effect is when short wavelength visible light energy enters the atmosphere, gets absorbed by the Earth’s surface, and is reradiated as longer wavelength infrared heat energy.  Water vapor and carbon dioxide in the atmosphere absorb the heat, trapping it in the atmosphere, thus warming up the Earth. It is called the “greenhouse effect” because the same thing happens to light, heat, and glass in a greenhouse.  It is a concern because burning fossils fuels and destroying rain forests increases the amount of carbon dioxide in the atmosphere, thus increasing the amount of heat trapped in the atmosphere and causing the Earth’s temperatures to rise (at least in theory).
        • Energy can be transferred from one place to another by:
        • conduction -- molecules vibrate and collide, passing on energy as they move [this works best with solids because molecules are close together]  (think of molecules as box cars and the train conductor)
        • convection -- molecules move because of differences in temperature which cause differences in density: hot ones rise, cold ones sink [this works best with gases and liquids where molecules are free to move around]  (think of a convection oven: air circulates in the oven)
        • radiation -- requires no molecules to move, just energy waves [ex/ sunlight, starlight]
    • TOPIC 6:  INSOLATION AND THE EARTH’S SURFACE
      • Insolation:  incoming solar radiation   (radiation from the Sun that reaches Earth)
        •  The greatest intensity of insolation is in the visible light wavelength part of the spectrum
        • Intensity of insolation increases with an increase in the angle of the Sun’s rays  (greatest intensity of the day occurs at noon when the sun is highest in the sky; greatest intensity for the year occurs for us on June 21 when the Sun reaches its highest altitude in the sky)
        • The angle of the Sun’s rays depend on latitude and season (we have summer in June - July because the angle of the Sun’s rays is greatest;  southern hemisphere has winter then because Sun’s rays are at a lower angle. The poles never get very warm because the angle is never very high)
        • Duration of insolation:  length/hours of sunlight  -- the longer the Sun’s path in the sky during the day, the longer the period of daylight (June 21 is longest for northern hemisphere)
        •  Insolation raises the Earth’s temperature, terrestrial radiation (heat given off by the Earth) cools it down
      •  Most of the ultraviolet light is absorbed by ozone in the atmosphere
      •  Most of the infrared energy is absorbed by water vapor and carbon dioxide in the atmosphere
      •  Clouds reflect about 25% of insolation
      •  The lower the angle of insolation, the more reflection occurs  
      • Materials that are dark and rough are good absorbers and radiators of energy;  materials that are light colored and smooth are good reflectors of energy
      •  Aerosols (fine particles of ice, dust, pollen, smoke, etc. in the atmosphere) scatter insolation, decreasing the amount of insolation that reaches the Earth’s surface (that’s why volcanic eruptions often make temperatures cooler)