Chapter 1: Introduction to Earth McKnight’s Physical Geography: A Landscape Appreciation, Tenth Edition, Hess

© 2011 Pearson Education, Inc. Introduction to Earth Geography as a Field of Learning Science and Geography The Environmental Spheres The Solar System The Size and Shape of Earth The Geographic Grid Earth-Sun Relations The Annual March of the Seasons Telling Time © 2011 Pearson Education, Inc.

Geography as a Field of Learning Definition Sciences which branch from geography Physical versus cultural “Why what is where and so what?” © 2011 Pearson Education, Inc.

© 2011 Pearson Education, Inc. Science and Geography The Scientific Method Observe phenomena Formulate a hypothesis Design an experiment Predict the outcome of the experiment Conduct the experiment Draw conclusions Scientific “proof” © 2011 Pearson Education, Inc.

© 2011 Pearson Education, Inc. Science and Geography Measurement Systems Need measurement systems to quantify scientific processes SI versus English units Conversions © 2011 Pearson Education, Inc.

The Environmental Spheres Four primary spheres atmosphere—“air” lithosphere—“stone” hydrosphere—“water” biosphere—“life” 1 4 2 3 Interactions between the spheres © 2011 Pearson Education, Inc.

© 2011 Pearson Education, Inc. The Solar System Formation of the Solar System Formed 4.5 to 5 billion years ago 8 planets revolve around the Sun 4 terrestrial planets 4 gas giants Earth is the third planet Figure 1-4 © 2011 Pearson Education, Inc.

© 2011 Pearson Education, Inc. The Solar System Figure 1-5 © 2011 Pearson Education, Inc.

The Size and Shape of the Earth Earth’s Physical Characteristics Equatorial diameter ~ 12,756 km Polar diameter ~ 12,714 km Circumference of 40,000 km Maximum relief Figure 1-6 © 2011 Pearson Education, Inc.

© 2011 Pearson Education, Inc. The Geographic Grid Location on Earth Need an accurate location on Earth to describe geographic features Use Earth’s rotation axis to base location on the surface North Pole and South Pole Plane of the Equator—halfway between poles and perpendicular to Earth’s surface graticule Figure 1-9 © 2011 Pearson Education, Inc.

© 2011 Pearson Education, Inc. The Geographic Grid Great Circles Circles which bisect a sphere and pass through the sphere’s center Identify the shortest distance between two points on a sphere—great circle distance Circle of illumination Small circles Figure 1-10 © 2011 Pearson Education, Inc.

© 2011 Pearson Education, Inc. The Geographic Grid Latitudes Parallels angle north or south of the equator 7 important latitudes: Tropic of Cancer and Capricorn (23.5° N and S) Equator (0°) Poles (90° N and S) Arctic and Antarctic Circles (66.5° N and S) Latitude zones Figure 1-12 © 2011 Pearson Education, Inc.

© 2011 Pearson Education, Inc. The Geographic Grid Longitudes Meridians Prime Meridian (0° longitude) located at Greenwich, England angle east or west of the Prime Meridian Converge at the poles Figure 1-16 © 2011 Pearson Education, Inc.

© 2011 Pearson Education, Inc. Earth-Sun Relations Rotation of the Earth 24 hours for one rotation Circular motion at all latitudes but the poles Rotation is counterclockwise relative to the North Pole Converge at the poles Diurnal transition from light to darkness Tidal effects from the Moon and Sun © 2011 Pearson Education, Inc.

© 2011 Pearson Education, Inc. Earth-Sun Relations Earth’s Revolution around Sun One revolution takes 365 ¼ days Elliptical orbit Aphelion (152,171,500 km) Perihelion (147,166,480 km) Average distance (149,597,892 km) Earth at perihelion during Northern Hemisphere winter; aphelion during Northern Hemisphere summer Figure 1-19 © 2011 Pearson Education, Inc.

© 2011 Pearson Education, Inc. Earth-Sun Relations Orbital Properties Plane of the Earth’s orbit is the plane of the ecliptic Earth’s axis tilted at 23.5° Plane of ecliptic is not parallel to equatorial plane Polarity of the Earth’s axis Parallelism North Pole always points toward Polaris (“North Star”) Figure 1-20 © 2011 Pearson Education, Inc.

The Annual March of the Seasons Three important conditions Declination of the Sun Solar altitude Length of day Two solstices June solstice December solstice Two equinoxes March equinox September equinox Figure 1-22 © 2011 Pearson Education, Inc.

The Annual March of the Seasons June solstice Occurs on approximately June 22 each year Sun is directly overhead at 23.5° N latitude Antarctic Circle in 24 hours of darkness Marks start of summer in Northern Hemisphere; winter in Southern Hemisphere Figure 1-22 © 2011 Pearson Education, Inc.

The Annual March of the Seasons December solstice Occurs on approximately December 22 each year Sun is directly overhead at 23.5° S latitude Arctic Circle in 24 hours of darkness Marks start of winter in Northern Hemisphere; summer in Southern Hemisphere Figure 1-22 © 2011 Pearson Education, Inc.

The Annual March of the Seasons Equinoxes Occur on approximately March 21 and September 21 each year Day length is 12 hours worldwide (“equinox”) Sun is directly overhead at the equator Figure 1-22 © 2011 Pearson Education, Inc.

The Annual March of the Seasons Day length Always 12 hours at the equator In the Northern Hemisphere, day length increases after March equinox Maximum day length during June solstice in Northern Hemisphere Opposite for Southern Hemisphere © 2011 Pearson Education, Inc.

The Annual March of the Seasons Significance of seasonal patterns Spread of solar rays over small and large areas Tropical latitudes consistently warmer Polar latitudes consistently cooler Large seasonal variations in temperature in midlatitudes © 2011 Pearson Education, Inc.

© 2011 Pearson Education, Inc. Telling Time Three physical measures of time Tropical year Lunar month Solar day Solar noon Sun casts the shortest shadow Ante-meridian (AM—“before noon”) Post-meridian (PM—“after noon”) Figure 1-23 © 2011 Pearson Education, Inc.

© 2011 Pearson Education, Inc. Telling Time Current time system 24 time zones Greenwich Mean Time (GMT) is standard Controlling Meridian for each time zone Several countries have multiple time zones in their borders Time zone boundaries subject to local political and economic boundaries of different nations 180° meridian chosen as the International Date Line © 2011 Pearson Education, Inc.

© 2011 Pearson Education, Inc. Telling Time Time zones of the world Figure 1-24 © 2011 Pearson Education, Inc.

© 2011 Pearson Education, Inc. Telling Time Time zones of the United States Figure 1-25 © 2011 Pearson Education, Inc.

© 2011 Pearson Education, Inc. Telling Time Daylight-saving time Move clocks ahead by an hour during the summer months Originally done by Germans during WWII; now practiced by many nations Conserves lighting energy by providing an extra hour of daylight Used No longer used Never been used © 2011 Pearson Education, Inc.

© 2011 Pearson Education, Inc. Summary Geography is the study of the distribution of physical and cultural attributes of Earth Many sciences have branched off of geography The scientific method is important when doing scientific studies Earth has four primary spheres: the atmosphere, the lithosphere, the hydrosphere, and the atmosphere The solar system formed 5 billion years ago and consists of 8 planets © 2011 Pearson Education, Inc.

© 2011 Pearson Education, Inc. Summary Earth is an imperfect sphere A latitude and longitude grid help identify locations on Earth’s surface Earth rotates on its axis in 24 hours Earth revolves around the Sun in 365 ¼ days Tilt of Earth’s axis causes seasons Equinoxes and solstices help identify when a seasonal transition occurs © 2011 Pearson Education, Inc.

© 2011 Pearson Education, Inc. Summary Time zones were established to have a uniform global time system Daylight-saving time was devised to conserve energy by adding an hour of daylight © 2011 Pearson Education, Inc.