Chapter 1 Study Notes: Planet Earth

CHAPTER 1: Planet Earth

THE SHAPE OF EARTH

  • A model is a representation of an object or a natural event.
  • Various models depict Earth as round, similar to a ball or a sphere.
  • For most applications, these models accurately represent Earth's shape as it is nearly a perfect sphere.
  • Actual Shape: Earth is classified as an oblate spheroid, which is slightly flattened at the poles and bulging at the equator.
    • Evidence for Oblateness:
    • Earth's "out of roundness" should not be overstated; the evidence supports that Earth appears almost spherical.
  • From a surface perspective, Earth might seem flat, but it has a diameter of nearly 13,000 kilometers (8000 miles).
    • Because of Earth's daily rotation, it bulges by approximately 40 kilometers at the equator.
    • When viewed from outer space, Earth appears perfectly round and smooth, with even the tallest mountains being minor in comparison to the planet's overall size.
  • Evidence of Earth's Shape:
    • Photographs from outer space consistently depict Earth as round.
    • Observing shifts in the positions of the sun and stars (especially Polaris) supports the spherical model.
    • As one travels considerable distances on Earth, one can observe consistent angular shifts in the altitude of Polaris, aligning with the spherical planet's expected behavior.

DIAMETER AND CIRCUMFERENCE

  • Measurements of Earth, both from the surface and orbiting satellites, reveal crucial facts:
    • Diameters & Circumferences of Earth:
    • Polar Diameter: 12,714 km
    • Equatorial Diameter: 12,756 km
    • Polar Circumference: 40,008 km
    • Equatorial Circumference: 40,076 km
  • Density Layers: Earth's internal structure shows that layers become progressively denser towards the center, with less dense layers always sitting atop more dense layers.

THE STRUCTURE OF EARTH

  • Earth's structure is generally divided into three principal parts:
    • Lithosphere (solid)
    • Hydrosphere (liquid)
    • Atmosphere (gas)
LITHOSPHERE
  • The lithosphere includes the dense, solid outer shell of Earth consisting of rock and soil, surrounding more fluid inner layers.
  • Thickness: The lithosphere's thickness varies from approximately 70 to 150 kilometers.
  • Composition:
    • Primary elements include oxygen and silicon, with smaller quantities of aluminum, iron, and calcium.
HYDROSPHERE
  • The hydrosphere comprises all water on Earth, including oceans, lakes, rivers, and groundwater.
  • Oceans have an average depth of 3-5 kilometers and cover about 70% of Earth's surface.
  • Water is a chemical compound made of oxygen and hydrogen, with various elements present in solution.
ATMOSPHERE
  • The atmosphere is the gaseous shell surrounding Earth, extending several hundred kilometers into space, and is layered into zones.
  • Principal Atmospheric Layers:
    • Troposphere: Closest layer to Earth's surface, vital for life, extending approximately 12 kilometers high, containing essential gases:
    • 78% nitrogen
    • 21% oxygen
    • Remaining gases include water vapor, carbon dioxide, argon, and neon.
    • Notable for its weather phenomena and turbulence.
    • Tropopause: Boundary between the troposphere and stratosphere.
    • Stratosphere & Above: Further boundaries include the stratopause (between stratosphere and mesosphere) and the mesopause (between mesosphere and thermosphere).
QUESTIONS
  1. According to the Earth Science Reference Tables, as the elevation above sea level in Earth's atmosphere increases, the measured atmospheric pressure will: (1) decrease (2) increase (3) remain the same
  2. Which part of the atmosphere has the smallest vertical distance from the bottom to the top of its zone? (1) troposphere (2) stratosphere (3) mesosphere (4) thermosphere
  3. The hydrosphere is mostly: (1) solid rock (2) liquid water (3) gaseous air
  4. Nitrogen is the most abundant element in: (1) crust (2) hydrosphere (3) troposphere (4) mantle
  5. Most of the water vapor in the atmosphere is found within: (1) mesosphere (2) thermosphere (3) troposphere (4) stratosphere
  6. Sequence of Earth layers in order of increasing average density? (1) atmosphere, hydrosphere, lithosphere (2) hydrosphere, lithosphere, atmosphere (3) lithosphere, atmosphere, hydrosphere (4) atmosphere, lithosphere, hydrosphere
  7. Which model shows best the volume of each gas found in the troposphere?

LOCATING POSITIONS ON EARTH

  • Scientists have established a coordinate grid as a system for locating positions globally based on latitude and longitude.

  • Coordinates Defined:

    • A pair of numbers representing every location on Earth.

  • Latitude:

    • Reference line for latitude based on Earth's rotation, determining positions of North and South Poles.
    • The Equator is the reference line/circle midway between the poles with a latitude of zero degrees (0°).
    • Lines of latitude are parallel to the equator, known as parallels.
    • Maximum latitudes: 90° N (North Pole) and 90° S (South Pole).

  • Longitude:

  • An arbitrary reference line, the Prime Meridian, runs from the North Pole to the South Pole through Greenwich, England.

  • Longitude measures angular distance in degrees east or west of the Prime Meridian, defined at zero degrees (0°).

    • The farthest longitude can be measured is 180°, with locations defined as either east or west.
  • Navigation is the process of determining one's location on Earth using coordinates.
    • Each location is defined by latitude (angle north/south of the equator) and longitude (angle east/west of the Prime Meridian).
    • The angle of latitude corresponds with Polaris's angular elevation above the horizon.
    • For example, New York City has a latitude of 40° N, with Polaris's angle above the horizon.
    • To find Polaris, locate the Big Dipper's pointer stars.
SOLAR TIME AND CLOCK TIME
  • Earth's clock system is based on the sun's position.
  • Noon is defined as the highest point of the sun in the sky.
  • The day is divided into 24 hours, each further divided into minutes and seconds.
  • Example: Calculating longitude from local and Greenwich time.
    • Formula: Longitude = (Time Difference in Hours) × 15° per hour.
  • If local time is earlier than Greenwich, the locale's longitude is west; if later, it is east.
QUERIES BASED ON OBSERVED STARS
  1. Polaris is a critical reference for latitude because it (1) rises at sunset and sets at sunrise (2) is located directly over Earth's rotation axis (3) can be observed from everywhere (4) is particularly bright.
  2. If a user knows solar time at the Prime Meridian, they can ascertain their: (1) date (2) altitude of Polaris (3) longitude (4) latitude
  3. As one moves along the equator, local solar time differences indicate one's longitudinal distance.

TOPOGRAPHIC MAPS

  • Topographic maps elucidate Earth’s contours, revealing shapes and elevations.
  • Contour Lines:
    • Connect points of equal value, indicating elevation changes.
    • Contour Interval: The height difference represented between adjacent contour lines.
    • Closeness of lines indicates steepness or gentleness of slopes.
LANDSCAPE FEATURES RECOGNITION
  • Recognizable features include hills, valleys, and slopes dictated by contour proximity.
GRADIENT DETERMINATION
  • The gradient expresses the rate of change in field value, calculated as: ext{gradient} = rac{ ext{difference in field value}}{ ext{distance}}
    • Example Calculation: If moving between two elevation points:
      ext{Gradient} = rac{980 m - 480 m}{4 km} = 125 m/km
CHAPTER REVIEW QUESTIONS
  1. Travel direction along Earth's surface without changing latitude? (1) East (2) South (3) Southeast (4) Northwest
  2. Pie chart depicting ocean elemental composition? (1) Oxygen (2) Hydrogen (3) Other elements
  3. Best scale model of Earth? (1) Dried apple (2) Warped golf ball (3) Bowling ball (4) Pizza
  • Lessons on proficiency and practical applications involving the Earth Science Reference Tables and topographic analysis are encouraged throughout assessments.