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Earth Science

Discover the evidence that proves the Earth is a spherical oblate spheroid. Explore the layers of the Earth and understand how to determine positions using latitude and longitude. Learn how to read topographic maps and create profiles.

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Earth Science

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  1. Earth Science Chapter 2 Measuring Earth

  2. Shape of Earth • Evidence the Earth is spherical: • Photographs from space • Setting sunlight lingers on treetops, then hilltops, then clouds • Large objects appear/disappear over horizon • Eclipses • True shape of Earth is an oblate spheroid • (Flattened at poles - bulging at equator)

  3. Size of Earth • Earth’s structure • Earth is divided into several layers • Crust = 10 km thick in oceans and 65 km beneath continents • Mantle = 2850 km thick • Outer core = 2100 km thick • Inner core = 1400 km thick (radius)

  4. Size of Earth

  5. Size of Earth • Lithosphere • Continuous shell of rock around Earth • Mostly covered by soil and loose rock • Hydrosphere • Thin layer of water resting on the lithosphere • Covers about 70% of Earth’s surface • Atmosphere • Thin shell of gases held to Earth by gravity • Has layers and thins out as distance from Earth increases

  6. Size of Earth

  7. Determining Positions on Earth • Coordinate systems • Any system for assigning two numbers to every point on a surface • The system used on Earth’s is the latitude-longitude system with the equator and prime meridian as reference lines. • When writing coordinates, distance along the horizontal line (latitude) is first, followed by distance along vertical line (longitude).

  8. Determining Positions on Earth • Latitude • Angular distance in degrees, north or south of equator • Lines of latitude run east-west and are called parallels. • Equator = 0 o latitude • North Pole = 90 oN latitude • South Pole = 90 oS latitude • Observer’s latitude in Northern Hemisphere is equal to altitude of Polaris (North Star).

  9. Determining Positions on Earth • Measuring Latitude

  10. Determining Positions on Earth • Longitude • Measurement of the angular distance east or west of the Prime Meridian • Lines of longitude run north-south and are called meridians. • Prime Meridian = 0 o longitude • International Date Line = 180 o longitude • All other readings need to be labeled east or west

  11. Determining Positions on Earth • Measuring Longitude • Local noon or solar noon is when sun is at its highest point at a given location. • Local noon changes one hour for each 150 longitude (3600 in sphere/24 hours in day) • In western hemisphere, local time is earlierthan Greenwich time; in eastern hemisphere, local time is later than Greenwich time.

  12. Determining Positions on Earth

  13. Mapping Fields • Isolines • Lines connecting points of equal values • Isolines connecting points of equal barometric pressure are called isobars. • Isolines connecting points of equal temperature are called isotherms. • On a topographic field (map), lines joining points of equal elevation are called contour lines.

  14. Mapping Fields • Gradient • The rate of change of a field quantity between two places • Gradient = change in field value distance • Example: If a map shows a stream drops 200m between two points 5km apart. What is the gradient? • 40 m/km

  15. Using Topographic Maps • Contour Maps (topographic maps) • A two-dimensional model, which shows the elevations of various points on the earth surface. • Contour lines pass through points with equal elevations. • The zero contour line is at sea level. • The difference between contour lines is the contour interval.

  16. Using Topographic Maps • Map Features • Depressions (holes) • To show these holes hachured lines I I I I I I are used • First hachure line has the same value as the lowest contour line between which it is found • Each additional hachure line inside the first has a lower value equal to the contour interval.

  17. Using Topographic Maps

  18. Using Topographic Maps • Map Scale • Relationship between a distance as measured on the map and the actual distance on Earth’s surface • Common ratio is 1:63,360 (1 inch = 1 mile) • Map Slope (Gradient) • Closely spaced contour lines = steep slope • Widely spaced contour lines = gentle slope

  19. Using Topographic Maps

  20. Using Topographic Maps • Map Key • Includes symbols for various features • Finding Direction • Maps usually oriented so north is top of page • Check for arrow pointing north to verify • Direction of Stream Flow • Streams always flow downhill • The contour lines bend upstream

  21. Using Topographic Maps

  22. Using Topographic Maps • Profile • Side view of the Earth’s surface • To Make a profile: • Place a strip of paper along the imaginary line on your contour map • Mark the paper wherever it crosses a contour line • Label marks with values of contour lines • Place strip of paper along bottom of graph • Label vertical axis of graph and project marks upwards to locate points of the profile • Connect the marks with a smooth curve

  23. Using Topographic Maps • http://www.uwsp.edu/geo/faculty/ritter/geog101/textbook/how_to/topographic_profile.html

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