Unit I: Earth Dimensions Review Book pp.19-30
Objective #1 Describe the actual shape of the Earth and explain 3 pieces of evidence for its actual shape.
Earth s Shape The Earth appears to be the shape of a sphere (round in circumference) when observed from space or scaled down to a model such as a globe. Taken from http://earthobservatory.nasa.gov/iotd/view.php?id=8108 on 8/30/11.
However, by actual measurement, the Earth is not a perfect sphere. Instead it has an oblate shape, having a larger circumference around the equator than through the poles. Taken from http://scienceblogs.com/startswithabang/2010/11/weekend_diversion_save_the_wor.php on 8/30/11.
Equatorial circumference = 40,076 km Equatorial diameter = 12,756 km Polar circumference = 40,008 km Polar diameter = 12,714 km Taken from ccrpc.org on 8/30/11.
Therefore the Earth is slightly bulged at the equator and slightly flattened at the poles. Thus the true shape of the Earth is best called an oblate spheroid. Taken from http://www.onr.navy.mil/focus/spacesciences/observingsky/precession2.htm on 8/30/11.
Evidence for the Shape of the Earth Taken from http://astrobob.areavoices.com/2009/02/17/spectacular-photo-inspires-a-northern-journey/ on 8/30/11. Animation Observations of the North Star (Polaris) Polaris lies in space practically over the geographic north pole of the Earth.
Altitude Angle above the horizon measured in degrees. Latitude Position north or south of equator in degrees. Taken from http://oxford-materialstechniques.com/data/illust/019920568x/019920568x.latitude.1.jpg on 8/30/11. Taken from http://www.nmm.ac.uk/upload/img/altaz-star2.jpg on 8/30/11.
If Earth is a perfect sphere, the altitude of Polaris should be equal to the latitude of the observer on Earth. These two measurements are not exactly the same so therefore, Polaris gives evidence that Earth is not a perfect sphere; but instead it is slightly out of round or oblate. Taken from http://bdaugherty.tripod.com/gcseastronomy/images/fifty.jpg on 8/30/11. Kid on a Bike
Photographs of Earth from Space When photos of the Earth taken in space are precisely measured, they show the Earth to be larger at the equator and flatter at the geographic poles. However, when drawn to scale on a piece of paper, the Earth appears to be perfectly round. Taken from http://earthobservatory.nasa.gov/iotd/view.php?id=8108 on 8/30/11.
Gravimetric (Gravity) Measurements Gravity Force of attraction between any 2 objects Since Earth has a large mass, smaller objects with less mass are pulled towards the Earth. Taken from http://www.bbc.co.uk/schools/ks2bitesize/science/images/earth_gravity.gif on 8/30/11.
Law of Gravitation Gravitational force is proportional to the inverse square of the distance between 2 centers of attracted objects. Taken from http://www.physicsclassroom.com/class/circles/u6l3c2.gif on 8/30/11.
So therefore, gravity and weight of an object anywhere on the surface of the Earth should remain the same (if the Earth is a perfect sphere). Taken from http://xamplified.com/wp-content/uploads/2009/02/acceleration-due-to-gravity1.jpg on 8/30/11.
Precise measurements show that gravity does on remain the same. Objects located at the poles weigh more than the same object located at the equator. This difference is more than can be expected due to the centrifugal effect. Taken from http://www.mrsciguy.com/sciimages/weight.jpg on 8/30/11.
Centrifugal effect Produced by Earth s rotation, pushes objects away from the center Examples Amusement park rides like Gravitron or Round Up Spinning bucket of water trick (here) Taken from http://home.bway.net/rjnoonan/humans_in_space/gravity.gif on 8/30/11. Taken from http://startswithabang.com/?p=1718 on 8/30/11. Taken from http://www.pswleisure.co.uk/images/fairground/large/roundupfairground-ride.gif on 8/30/11.
Objective #2 Name the 3 spheres of the Earth and describe their unique characteristics. Be able to use ESRT p.14 to describe the atmosphere.
Spheres or Parts of the Earth The atmosphere extends several hundred km above the Earth s surface into space and is the least dense of the 3 spheres. Atmosphere Hydrosphere Lithosphere Taken from need-media.smugmug.com on 8/30/11.
Earth s Atmosphere Atmosphere is the Air The atmosphere is stratified (layered) into 4 zones each possessing distinct characteristics. ESRT p.14.
Troposphere Most dense layer of atmosphere Lowest section of the atmosphere found between the Earth s surface and the tropopause It is characterized by decreasing temperature with increasing altitude. The only zone of the atmosphere to contain water vapor.
Stratosphere Region above the troposphere and below the mesosphere where temperature increases with altitude due to the presence of ozone.
Mesosphere Found above the stratopause and below the mesopause. Characterized by temperatures that decrease with an increase in altitude.
Thermosphere Lease dense layer of atmosphere Outermost zone found between mesopause and outer space where temperature steadily increase with altitude. According to ESRT p.14, what happens to Atm. Pressure as you increase in altitude through each of the zones? Atmospheric pressure constantly decreases.
Note that the temperature pauses then reverses direction when switching from one layer to the next. Now you know why they call it the Tropopause.
Earth s Hydrosphere Hydro means water, think hydrant or hydroelectric. What is Earth s nickname? Taken fromhttp://www.waterdeva.com/blog/wp-content/uploads/blue-planet.jpg on 8/30/11. Approximately 71% of the Earth s surface is covered with a relatively thin layer of water. (More dense than atmosphere) Includes marine (salt water) and freshwater (inland lakes and rivers).
Earth s Lithosphere Lithosphere is Land Lithosphere Continuous, outer solid rock shell of the Earth The lithosphere is often under the hydrosphere (More dense) and accounts for the general features such as mountains, valleys and the ocean floor. Taken from http://www.physicalgeography.net/fundamentals/images/lithosphere.gif on 8/30/11.
Objective #3 Describe a coordinate system and be able to use latitude and longitude (degrees & minutes) to determine a position on Earth.
Earth Positions Coordinate System Uses a grid of imaginary lines and two points called coordinates. A fixed point can be located on a graph by identifying the axes ( the intersecting point of two lines). Taken from http://www.euclideanspace.com/threed/solidmodel/geospatial/ellipsoid/earth.gif on 8/30/11.
What is the most commonly used coordinate system for identifying points on Earth s surface? Latitude and Longitude Axes used are called parallels & meridians. Coordinate system based on observations of the Sun & other stars.
Parallels of Latitude The equator, located halfway between the geographic poles, is a circle which divides the Earth into the Northern and Southern hemispheres. Lines called parallels are drawn. These parallels decrease in size from the equator (0 o ) to the North Pole (90 o N) and the South Pole (90 o S). Taken from http://www.smallboatgps.com/class/index_files/image002.gif on 8/30/11.
Meridians of Longitude Lines connecting the North Pole and South Pole are called meridian. The Prime Meridian runs through Greenwich, England and has a longitude of 0 o. Longitude is measured using the meridians, east or west of the the Prime Meridian (0 o ) to a maximum of 180 o (the International Dateline). Taken from http://www.sailingissues.com/nav2n.png on 8/30/11.
Latitude & Longitude Measurements Latitude and Longitude are measured in degrees. Latitude is degrees north or south of the equator. Longitude is degrees east or west of the Prime Meridian. Taken from math.nus.edu.sg on 8/30/11.
Latitude is often determined by using the altitude of Polaris above the horizon in the Northern hemisphere. In the Southern hemisphere, other stars are used. Taken from http://astrobob.areavoices.com/2009/02/17/spectacular-photo-inspires-a-northern-journey/ on 8/30/11.
Longitude is based on the Sun. The Earth rotates from west to east, 360 o in a 24 hour period of time. How many degrees is that every hour? Taken from resonanceswavesandfields.blogspot.com on 8/30/11.
Objective #4 Be able to relate longitude positions and time differences.
Comparing local time to GMT or UT allows you to find your longitude. Every hour difference from GMT indicates 15 o difference in longitude from the Prime Meridian. Each hour earlier than GMT indicates 15 o west of Prime Meridian. Each hour later than GMT indicates 15 o east of Prime Meridian. earlier later
U.S. Time Zones Taken from http://www.socialstudiesforkids.com/graphics/timeszones_us.gif on 8/30/11.
Taken from http://wiki.naturalfrequency.com/files/wiki/solar/time-zones.gif on 8/30/11. Example: A clock indicates it is 4 hours later than GMT. What is your longitude?
Modern navigational techniques such as GPS (Global Positioning System) uses signals from both Earth and orbiting satellites to determine latitude and longitude. Taken from http://www.colorado.edu/geography/gcraft/notes/gps/gif/figure05.gif on 8/30/11.
Objective #5 Be able to read and use field (contour or topographic) maps. Objective #6 Know the following terms and be able to apply them to a map: field, isolines, gradient, contour interval, hachure marks
Position Charactertistics Field Region of space that contains a measurable quantity at every point. Examples/Types of Fields Gravity Sample Field Model Magnetic Atmospheric Pressure Relative Humidity Temperature Pollen Count Snow Cover or Depth
Isolines Connect points of the same value Isobars Lines connecting points with same atmospheric pressure Contour lines Lines connecting points with same elevation Isotherms Lines connecting points with same temperature Taken from http://www.mrsciguy.com/sciimages/isoline.gif on 8/30/11. Taken from weather.com on 8/30/11. Taken from topozone.com on 8/30/11. Taken from http://www.nc-climate.ncsu.edu/secc_edu/images/isobarsisotherms.gif on 8/30/11.
Isolines represent field characteristics in 2 dimensions. Isosurfaces represent field characteristics in 3 dimensions. Taken from https://www1.nga.mil/kids/geoint/photodict/publishingimages/ dict-contourlines.jpg on 8/30/11. Taken from http://www.berneda.com/teechart_vcl_features/images/seriestypeisosurface.png on 8/30/11.
Taken from http://www.geoblox.com/images/jetty_image.jpg on 8/30/11. Taken from http://img.tgdaily.net/sites/default/files/imagecache/story_slid er/stock/450teaser/space/galaxy_simulation.jpg on 8/30/11. Isoline maps and isosurfaces are examples of models. What is a model? Simplified representation of objects, structures or systems.
Field Changes Static Unchanging Dynamic Constantly changing Of these two terms, which one describes almost all fields? dynamic
Objective #7 Use the gradient formula to solve problems.
Gradient Average slope within field, shows rate of change of field from one place to another Formula ESRT p.1
Gradient Example Solve using 3 step method (Formula, Substitution & then answer with label).
Calculate the pressure gradient along a straight line between point A and point B on the map. Solve using the 3 step method.
When isolines are closer together the gradient is steep and when the isolines are further apart, the gradient is shallow (less).
Contour (Topographic) Map Uses isolines (contour lines) to connect points of same elevation, usually based on sea level measurements. Taken from http://www.adirondacknorthway.com/maps/mtmarcysm.jpg on 8/30/11.
Generally every 5 th line is an index contour line. These lines are printed darker and give the elevation value. Taken from http://www.therockerbox.com/contour_lines_a3.jpg on 8/30/11.
Contour interval Difference in elevation between two consecutive contour lines.
Hachure marks indicate downward slope and are represented by the following symbol..
What advantage is there to using a topographic map rather than an ordinary road map? Taken from http://pics.city-data.com/topo/tpc15669.png on 8/30/11. Topos show terrain or land surface.
Objective #8 Make a profile from a contour map.
What is a profile? Vertical cross-section of land surface between 2 points on a map. a side-view of map
Steps for making a profile. 1. Place straight edge of scrap paper between the 2 points on the map. 2. Wherever contour line meets edge of paper, place a mark on scrap paper and record elevation of that point. 3. Take scrap paper with all the marks against horizontal axis of graph. 4. Above each mark on scrap paper, plot point on graph according to vertical axis. 5. Connect all points with smooth line. (Remember to curve all peaks and valleys!)