Shape of Earth, Cycles, Distribution of Water 1 What is the shape of Earth? A. Spherical B. Apple-shaped C. Pear-shaped 2 Draw shape of the Earth 3 1
Shape of the Earth It should be spherical: Earth condensed under gravity, thus everything making the Earth would be pulled toward the center of mass. However, there are complexities Rotation of Earth distorts the sphere by a centrifugal effect. If solely gravity and rotation acted on the shape of the Earth, it would be an oblate spheroid Density variations within the Earth distort Earth s gravity. This distortion (combined with rotation) result in a shape similar to a pear 4 Shape of Earth results from distorted gravity and rotation of the earth Earth is shaped like a pear. Notice the shape deviates from the oblate spheroid (dashed line): Deviation is on the order of 10s of meters This is minor relative to the radius of the Earth (1.6e-4%) low places like South Pole and the northern hemisphere are due to low density continents effecting gravity variations King-Hele, 1969 5 Which direction does Earth rotate? A. West B. East C. Depends on your perspective relative to the North Pole or the South Pole 6 2
How Fast does Earth rotate? A. 10º/hour B. 15º/hour C. 180º/hour D. 360º/hour 7 Earth s roughness or topography Highest mountain: Deepest trench: Radius at equator: Everest 8.85 km Mariana -11.2 km ~6370 km 8 Which has roughness similar to Earth? A. Tennis Ball B. Basketball C. Beach ball 9 3
Earth s roughness 1. Radius of Earth ~ 6370 km 2. Greatest relative relief: Everest - Mariana = 20.05 km (Or 0.3% or Earth s radius) 10 Distribution of Water: 1% of Fresh water 77% of Fresh water 22% of Fresh water 11 Hydrologic Cycle moves water between reservoirs video 12 4
The hydrologic cycle 60% 40% 84% evap Off oceans 75% precip Fall on oceans Transfer between Reservoirs Powered by? The Cycle: Evap. + Transpiration + Sublimation Precipitation 13 The Earth s Oceans: can you name them? 14 Earth s Oceans 15 5
Can you rank the oceans by area and depth? 16 How is location on the surface of Earth defined? 17 Latitude Lines 0º at equator increasing to 90º at poles 1º latitude = 60 nm = 111 km = 69 statute miles 1 nautical mile = 1 minute latitude What is Urbana s Latitude? 18 6
Longitude Lines Perpendicular to Latitude lines 0º = prime meridian Set at Royal Naval Observatory, Greenwich GMT=UT= Zulu 180º = int. date line 12:00 UT = new day at I.D.L. Question: Why can t you measure Longitude in miles? A. Because lines of longitude are not parallel to each other. B. Because the surface of the Earth is not flat. C. Because most of the world measures distance in kilometers. 19 How then, do you determine the latitude and longitude of your location? Latitude is relatively easy: there are two ways Observe the angle of the sun at Noon given knowledge of Suns path during year, you can calculate latitude. Or, determine the inclination of a compass needle Simple calculation will give latitude. The ecliptic (the suns path over the year). Longitude is tricky: This was a major problem - ships would easily be lost Galileo could do it. British Empire held a contest to solve this problem 1730, J. Harrison s Chronometer 20 Distortion! Caused by depicting globe on a FLAT surface Examples: Lay an orange peal flat Wrap a ball in paper The Problem with Maps 21 7
Projections limit distortion What is a projection? Place paper in contact with globe shine light from center onto paper Shadows = map Distortion is Minimized at contact Extreme away from contact Three types shown here Look at Greenland 22 Review Questions Why is the Earth not a perfect sphere? How are the cardinal directions defined? Which adjective best describes Earth s surface: bumpy, angular/spiky, smooth-as-silk. Where does water reside on Earth s Surface? How is the Sun involved in the Hydrologic Cycle? 23 Review Questions Why is the Southern Ocean not an ocean? Rank the oceans in order of decreasing volume. Compare the angle of rotation and the linear distance distance of rotation at the equator to that at 40º latitude. Why can t you measure longitude in miles, yet you can measure latitude in miles? Which type of map projection would be most useful to a polar explorer? 24 8