Topic 1: Introduction To Planet Earth

1. Topic 1: Introduction To Planet Earth • What is Physical Geography? • Why is Physical geography Important? • Introduction to Planet Earth- Earth in the Universe- The Solar System • Shape and Size of Planet Earth

2. Topic 1: Introduction To Planet Earth • The Geographic Grid System- Latitude and Longitude- Longitude and Time- International Dateline • Movements of the Earth- Earth’s Rotation and Effects- Earth’s Revolution and Effects

3. What is Geography • Geography is the study of the spatial and temporal distributions of:- all physical elements and - all human elementson the earth surface

4. Physical & Human Elements on Earth Surface

5. What is Geography? • It involves a clear understanding of:- why physical & human elements are located where they are- how they interact in space & time to give character to our landscape - how interactions among places organize the earth surface into spatial forms and patterns

6. What is Geography? - the processes responsible for and continually changing the spatial distributions and patterns of all geographic elements on earth • Hence, geographers are interested in:- "where" information or - place or location information and • - often associated with memorizing “place names”

7. What is Geography? • Physical geographers are interested in the distribution of all the physical elements broadly grouped into four spheres:- Atmosphere- Hydrosphere- Biosphere- Lithosphere, & labeled as Physical Geography • Physical Geography is natural science with a focus on the study of climate, soil, landforms, vegetation (i.e., biogeography)

8. What is Geography? • Today, the increasing role of human actions in changing the physical environment is becoming critical

9. Why is Physical Geography Important? • The course meets SIUE general education requirements • Improves our understanding of the physical environment and how it works • He us to understand that the physical environment is a resource as well as a source of natural hazards

10. Why is Physical Geography Important? • Improves our landscape appreciation and awareness • A useful guide to environmental planning and management

11. Earth in the Universe • The universe is organized into clusters of stars called Galaxies • We have billions of galaxies in the universe • There are over 100 billions of stars in some galaxies • Our sun is one of such stars in our galaxy called Milky Way Galaxy

12. Milky Way Galaxy: Thin Disk with a Central Bulge • The Universe is about 12-15 billion years old

13. The Milky Way Galaxy

14. Earth in the Universe • The Milky Way is a spiral galaxy, disk-shaped with a central bulge and about 100,000 light years across • One light-year is equal to 5.875trillion miles or 9.4 trillion kilometers per year • Our sun is located on one of the spiral arms called Orion arm

15. The Solar System The Solar System Consists of: • The sun (center of the solar system) and eight planets • Four inner planets of the solar system are called terrestrial planets: (Mercury, Venus, Earth and Mars)

16. The Solar System The Solar System Consists of: • >10,000 asteroids (asteroid belt between Mars and Jupiter)

17. An Asteroid With Impact Craters

18. The Solar System The Solar System Consists of: • meteorites (pieces of rocks and minerals frozen in gases) • Hale-Bopp Comet seen (1997) with long glowing tail due to ice vaporization

19. The Solar System The Solar System Consists of: • meteorites (pieces of rocks and minerals frozen in gases) • Hale-Bopp Comet seen (1997) with long glowing tail due to ice vaporization • natural satellites or moons (>64 moons) • all the planets formed same time from same general materials and move counterclockwise in an elliptical orbit around the sun

20. Solar Systems • Pluto is no longer regarded as a planet of the solar system

21. Solar Systems • Pluto is not part of our solar system because of: - its unique oblique orbital plane and - its relatively higher density, given its location

22. Solar Systems • This is the current composition of the solar system • All planets orbit in the same plane as the sun’s equator

23. Solar Systems • The Nebula theory is the most accepted explanation of how the solar system is formed • According to the Nebular hypothesis:- solar system evolved from rotating cloud of dust and gases called nebula- nebula contained mainly hydrogen and helium produced by the Big Bang- nebula began to contract at about 5 billion yrs ago

24. Solar Systems • According to the Nebular hypothesis:- nebula became flat and disk-shaped with the protosun at the center- inner planets began to develop from condensed rocky and metallic clumps with high melting point- strong solar winds removed the lighter gases like hydrogen and helium from the inner planets

25. Solar Systems • According to the Nebular hypothesis:- larger outer planets began to form from the lighter gases with a high percentage of ices or frozen gases – water, carbon dioxide, ammonia, and methane

26. Glowing nebular clouds of gases and dust particles become concentrated to form stars

27. Nebula contracted into a rotating disk and heated up as gravitational energy converts into heat energy Gravitational collapse of nebula causing its inward contraction Cooling nebula condenses to form tiny rocky and metallic solid particles Collision of dust-size particles join to form asteroids and accrete to form the planets

28. Features of Terrestrial Planets • Terrestrial planets: Mercury, Venus, Earth & Mars • Composed of minerals and rocky materials • more dense (>3gm/cm3) • Less oblate in shape (more nearly spherical) • Slower in rotation and Smaller in size • Diverse and shallow atmosphere

29. Common Features of The Planets

30. Features of Jovian Planets • consist of: Jupiter, Saturn, Uranus Neptune • much larger in size • composed entirely of gases and less dense • much more oblate and rotate more rapidly • dense and turbulent atmospheres

31. Shape of Planet Earth • Ancient Greek Scholars always believed that the earth is spherical in shape • In 200 B.C., Eratosthene estimated the circumference of the earth • The spherical shape of the earth is supported by:- lunar eclipse- circular horizon around the earth- satellite photographs of the earth- variations in the force of gravity, etc

32. Shape of Planet Earth • The spherical shape of the earth is caused by the gravitational attraction of earth’s materials • But the centrifugal force of earth’s rotation has distorted the shape from a perfect sphere • Hence, the earth bulges at the equator and flattens at the poles, a shape described as oblate spheroid

33. Shape of Planet Earth • The oblate spheroidal shape is supported by: - a polar diameter that is shorter than the equatorial diameter by 27 miles- a relatively lower value of gravity at the equator and a higher value at the poles

34. Oblate Spheroidal Shape of the Earth

35. Eratosthene’s Measurement of Earth’s Circumference • Eratosthene made his measurements in Egypt • Based his measurement on the geometric properties of a sphere • Measured an arc of a circle around the earth by measuring the distance between Alexandria and Syene (5000 stadia)

37. Eratosthene’s Measurement of Earth’s Circumference • He measured the angle subtended by the arc at the center of the earth by using:- solar elevations at Alexandria & Syene taken on summer solstice at noon - the properties of parallel lines • Solar elevation at Alexandria was 7.2o and vertical (90o) at Syene on the Tropic of Cancer (why?)

38. Eratosthene’s Measurement of Earth’s Circumference • Found the angle subtended by the arc at the center of the earth to be 7.2o • By extrapolation, he calculated earth circumference to be 250,000 stadia or 43,000 km (if one Attic stadium measured 184 m or 407 ft) • Earth’s actual circumference is 40,000km or 25,000 miles

39. Size of Planet Earth • Earth’s polar diameter: 7900 mi (12,714 km) • Equatorial diameter: 7927 mi (12,756 km) • Polar circumference: 24,819 mi (39,943 km) • Equatorial circumference 24,902 mi (40,0076 km) • Equatorial diameter is longer by 27mi or 42 km

40. The Geographic Grid System • The geographic grid system is also referred to as the Graticule • It consists of east-west lines (latitudes) and north-south lines (longitudes) • It is designed to intersect at right angles to permit precise location of points on the globe

41. The Geographic Grid System

42. The Geographic Grid System • The natural reference points for location measurements purposes include: - North Pole- South Pole- equator • The primary purpose of the grid system is for the precise location of points

43. Locating Points Using a Grid system

44. The Geographic Grid: Latitude • Latitudes are also called parallels of latitude because they don’t meet • it is a true east-west line • a line of latitude goes round the globe to form a full circle called circle of latitude • circles of latitude are progressively smaller towards the poles where it is a point

45. Parallel or Circle of Latitudes

46. The Geographic Grid: Latitude • largest circle of latitude is midway between the poles called the equator • the Equator is a Great Circle because it divides the globe into 2 equal parts • all other circles of latitude are small circles • A Great Circle is always the shortest route between 2 points and useful for navigation

47. The Geographic Grid: Latitude • Latitudes are measured in angular degrees north or south of the equator • Hence latitudes have values between 0o and 90o N or S of the equator • One degree of latitude is about 111 km (69 mi) space apart

48. Length of Degrees of Latitude & Longitude

49. The Geographic Grid: Latitude • Calculate the distance (in miles) between St. Louis, MO (39o & 90oW) and New Orleans LA (30o N & 90oW) as the crow flies (Hint: a degree of latitude is spaced about 111 km (69 mi) space apart) • First determine how many degrees of latitudes separate the two cities • Answer: _______(km)

50. The Geographic Grid: Important Latitudes • important latitudes: - Arctic Circle (66½o N)- Antarctic Circle, (66½o S) • - Tropic of Cancer (23½o N) • - Tropic of Capricorn (23½o S) - North Pole (90oN) • - South Pole (90o S)- Latitude of Edwardsville (38o 49’ N)