Introduction to the Earth
Introduction to the Earth
•The Environmental Spheres
•The Size and Shape of the Earth•The Geographic Grid
The Environmental Spheres
Lithosphere-describes the solid inorganic portion of the Earth (composed of rocks, minerals and elements). It can be regarded as the outer surface and interior of the solid Earth.Atmosphere-is the vast gaseous envelope of air that surrounds the Earth. Its boundaries are not easily defined. The atmosphere contains a complex system of gases and suspended particles that behave in many ways like fluids. Many of its constituents are derived from the Earth by way of chemical and biochemical reactions.
Hydrosphere-describes the waters of the Earth (see the hydrologic cycle). Water exists on the Earth in various stores, including the atmosphere, oceans, lakes, rivers, soils, glaciers, and groundwater. Water moves from one store to another by way of: evaporation, condensation,
runoff, precipitation, infiltration and groundwater flow.
Biosphere-consists of all living things, plant and animal. This zone is characterized by life in profusion, diversity, and ingenious complexity. Cycling of matter in this sphere involves not only metabolic reactions in organisms, but also many abiotic chemical reactions.
All of these spheres are interrelated by dynamic interactions (biogeochemical cycling)
The Size and Shape of the Earth
Pythagorus (ca. 580 -500 B.C., Greek) -first to note spherical character of the earth. This principle was widely accepted by 1st Century A.D. Columbus, for example, was well aware of sphericity of earth.
How to proof sphericity?
Ships “sinking” below the horizon as they sail into distance (Pythagorous).Curved shadow cast by earth during eclipse (Pythagorous).
Aerial/Space PhotosSunsets are gradualNavigation, which uses spherical trigonometry, works.North Star moves with latitude.
However, Pythagorous assumed spherical perfection. Sir Isaac Newton (1687) reasoned that sphere not possible since earth rotation is maximized at the equator and this should produce a ‘bulge.’ He called earth an oblate spheroid(think of spinning water balloon; Jupiter is egg-shaped enough to be noticeable through inexpensive telescope).
diameter: 8,000 miles (12,900 km)
circumference = d or 3.14 x 8,000 = 25,000 miles
Geoid -conceptualizes earth w/o imperfections.
In fact, if radius of earth was 30 story building, Mt. Everest would be only a single brick in height.
The Geographic Grid
Latitude -angular measurement of distance north or south of the Equator.
Range: 0 -90 degrees N or S
1o latitude = approx. 69 miles (25,000 mi. /360o).
Parallel -Imaginary lines that connect points of equal latitude.
These seven parallels represent special points where the Sun’s rays strike the earth.
Longitude - the angular measurement of distance east or west of the Prime Meridian.
Range: 0o-180oE or W
Maximum value reached at International Date Line -180o
East-west width of 1Olongitude for selected western North American cities:
San Diego (32.5 N) = 57 miles; San Francisco (38 N) = 54 miles; Seattle (48 N) = 46 miles; Anchorage (60 N) = 35 miles
Length of a Degree ofLongitude
Los Angeles County: 34o N, 118o W
Each degree is divided in 60 minutes(‘), thus we can locate Torrance at: 33o53’ N, 118o 19’ W
Each minute is further divided into 60 seconds(‘’), thus we locate El Camino College at:
33o 53’ 06” N, 118o 19’ 38” W
At this point we are accurate to within 100 ft2.
Degrees, Minutes, Seconds