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Geography as a Field of Learning

• Geography is a generalized discipline that has the face of planet Earth as its focus.

• Rooted in the Greek words for “earth description,” geography is the arealdifferentiation of Earth’s surface.

Vocabularyparallel (p. 11)perihelion (p. 17)physical geography (p. 1)plane of the ecliptic (p. 17)plane of the equator (p. 10)polarity (parallelism) of the

rotation axis (p. 18)prime meridian (p. 13)September equinox (p. 19)solar altitude (p. 18)South Pole (p. 11)Tropic of Cancer (p. 18)Tropic of Capricorn (p. 19)Universal Time Coordinated

(UTC) (p. 23)

hydrosphere (p. 5)inclination of Earth’s axis (p. 17)International Date Line (p. 24)international system of

measurement (SI) (p. 4)June solstice (p. 18)latitude (p. 11)lithosphere (p. 5)longitude (p. 13)March equinox (p. 21)meridian (p. 13)North Pole (p. 11)

Antarctic Circle (p. 18)aphelion (p. 17)Arctic Circle (p. 18)atmosphere (p. 5)biosphere (p. 5)circle of illumination (p. 18)cryosphere (p. 5)cultural geography (p. 1)December solstice (p. 19)equator (p. 10)graticule (p. 11)great circle (p. 10)Greenwich Mean Time (GMT)(p. 23)

Geography as a Field of Learning

• The fundamental questions of geographic inquiry are– “Why is What Where?”– “So What?”

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Geography as a Field of Learning

• Geography’s basic characteristics are as follows:– It looks at how things differ from place to place;– It has no peculiar body of facts or objects it can call

wholly its own;– It is a very broad field of inquiry and “borrows” its

objects of study from related disciplines;– It is both a physical science and a social science

because it combines characteristics of both and can be conceptualized as bridging the gap between the two;

– It is interested in interrelationships, that is, examining how various factors (both physical and cultural) interrelate.

Geography as a Field of Learning• Geography has two main

branches, Physical Geography and Cultural Geography:– Physical Geography—

also known as environmental geography, it looks at those Earth elements that are natural in origin;

– Cultural Geography—also known as human geography, looks at elements of human endeavor.

Science and Geography

• The subject matter of this class is physical geography.

• This class will focus on the Earth’s physical elements, specifically:– Their nature and characteristics, processes

involved in their development, their distribution, and their interrelationships.

– This class will also explore the ways humans have shaped the physical environment.

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Science as a Field of Learning• Science is described as a process that follows the

scientific method• Observe phenomena that stimulates a question or

problem• Offer an educated guess (hypothesis) about the answer• Design an experiment to test the hypothesis• Predict the outcome of the experiment• Conduct the experiment and observe the outcome• Draw conclusions and formulate rules based on the

experiment

Science as a Field of Learning

• Science does not always exactly fit this methodology (i.e., data collection can be through observation) and therefore science is best thought of as a process for gaining knowledge

• Although the term “scientific proof” is used, science does not actually prove things, but rather eliminates alternative explanations.

• Science is based on disproving these alternative explanations.

Science as a Field of Learning

• In science, theories represent the highest order of understanding in a body of information. – Theories are logical and well-tested

explanations encompassing numerous facts and observations.

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Science as a Field of Learning

• The acceptance of theories is based on evidence and not beliefs, nor the pronouncements of “authorities.”

• Theories are revised based on new observations and new evidence.

Science as a Field of Learning

• The scientific method is a self-correcting process based on the refining of scientific knowledge through peer review, which ensures that research and conclusions meet rigorous standards of scholarship.

• New scientific evidence may make scientists change their minds, as well as lead to disagreement within the scientific community, but good science tends to take a cautious stance toward conclusions that are drawn.

Science as a Field of Learning• As such, scientists preface findings by stating that “the

evidence suggests,” or “the results most likely show.”• This apparent circumspection can lead to a

misconception surrounding the validity of the scientific method on the part of the general public.

• However, this very circumspection spurs scientists to further seek knowledge and understanding.

• This class will present the fundamental of physical geography as supported by scientific research and evidence.

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Numbers and Measurement Systems

• This text offers measurements in both the International System of Units, from the French Système International (SI), and the traditional (or English) system.

• SI is an extension of the metric system, devised in the 1790s to provide simple and scientific standard units.– SI to English conversions may be found in

Tables 1-2 and 1-3, and in Appendix I.

Global Environmental Change• Some characteristics of the global environment have

been in a perpetual state of change.– The rate of change of some of these characteristics, however,

vary.– Throughout this book, the topic of global environmental

change—both natural and human induced—will be addressed.– Special attention is given to the accelerated effects of human

impact on the physical environment.• This topic is integrated in the various chapters within the

text and is dealt with more overtly in short, box essays titled “People and the Environment,” which focus on human-environment interrelations.

The Environmental Spheres

• Earth’s surface is a complex interface where four spheres meet, and to some degree overlap and interact. These four spheres provide important organizing concepts for the systematic study of Earth’s physical geography:– Lithosphere– Atmosphere– Hydrosphere

• A subcomponent of the hydrosphere that encompasses frozen water and snow is the cryosphere

– Biosphere

L

A H

B

Interacting spheres

LithosphereLitho, Greek for “stone”

Atmosphereatmo, Greek for “air”

Hydrospherehydro, Greek for “water”

Biospherebio, Greek for “life”

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The Solar System• The geographer’s

concern with spatial relationships properly begins with the relative location of Earth in the universe.– Solar system —

system of nine planets (and moons, comets, asteroids, meteors) revolving around the Sun; Earth is third.

The Solar System• Sun—medium-sized star

and makes up more than 99 percent of the solar system’s mass.– The Sun is one of perhaps

100,000,000,000 stars in the Milky Way Galaxy, which is one of at least a billion galaxies in the universe.

The Solar System• Earth’s planetary orbit lies in nearly the same plane as

all the other planets, except that of Pluto’s, which is somewhat askew.

• Earth, like all the planets, revolves from west to east. • Earth, like the Sun and most of the other planets, rotates

from west to east on its own axis.

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The Solar System• The terrestrial planets (the four inner planets —Mercury,

Venus, Earth, and Mars) are smaller, denser, and less oblate and rotate on their axes more slowly than the Jovian planets.

• Terrestrial planets are also comprised mainly of mineral matter.

The Solar System• The Jovian planets (the

four outer—Jupiter, Saturn, Uranus, and Neptune) are larger, more massive, less dense and more oblate than the terrestrial planets.

• Jovian planets are comprised mostly of gas. – In more recent years, more

small-sized “Pluto-like”dwarf planets and comets have been discovered in our solar system beyond Neptune in the Kuiper Belt

The Size and Shape of Earth• Frame of reference

determines whether one looks at Earth as being large or small.

• Earth is an oblate spheroid rather than a true sphere, though the variation from true sphericity is exceedingly minute, and so for most purposes it can properly be considered a sphere.

Earth

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The Size and Shape of Earth• Greek scholars as early

as six centuries B.C. began believing Earth was a sphere, with several making independent calculations of its circumference that were all close to reality.

• Eratosthenese did so by observing the angle of the Sun’s rays in Alexandria and Syene on the same day.

The Size and Shape of Earth• Earth shape is affected

by two main facts:– It bulges in midriff, because

of pliability of Earth’s lithosphere;

– Its shape is therefore an oblate spheroid.

– It has topographical irregularities.

• In context of Earth’s full dimensions, these variations are minute.

Oblate Ellipsoid: the shape of Earth

The Geographic Grid

• A system of accurate location is necessary to pinpoint with mathematical precision the position of any spot on Earth’s surface.

• The grid system is the simplest technique, using a network of intersecting lines.– Graticule—the grid system

for mapping Earth that uses a network of parallels and meridians (lines of latitude and longitude).

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• Geographic grid– Graticule– Parallels and meridians

– Fig. 1-18

The Geographic Grid• Four Earth features

provide the set of reference points essential to establish the graticuleas an accurate locationalsystem:

• North Pole, South Pole, rotation axis, and equatorial plane (an imaginary plane passing through Earth halfway between the poles and perpendicular to rotation axis).

The Geographic Grid• Equator—the imaginary midline of Earth,

where the plane of the equatorintersects Earth’s surface. Is the parallel of 0° latitude.

• Great Circle—the largest circle that can be drawn on a sphere; it must pass through the center of the sphere; it represents the circumference and divides surface into two equal halves or hemispheres.

• Circle of Illumination—a great circle that divides Earth between a light half and a dark half.

• Small circle—a plane that cuts through a sphere without passing through the center.

• Graticule — The grid system of the Earth consisting of lines of latitude and longitude.

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Latitude• Latitude—the distance measured north

and south of the equator; it is an angular measurement, so is expressed in degrees, minutes, and seconds.

• Parallel—an imaginary line that connects all points of the same latitude; because they are imaginary, they are unlimited in number.

• Seven parallels are particularly significant:– Equator, 0°– North Pole, 90° N– South Pole, 90° S– Tropic of Cancer, 23.5° N– Tropic of Capricorn, 23.5° S– Arctic Circle, 66.5° N– Antarctic Circle, 66.5° S

Latitude• This is the angular

distance of a point north or south of the equator.

• It increases from a minimum of 0° at the equator to a maximum of 90° at the north and the south poles.

• Lines of latitude are parallel to each other and describe circles that decrease in circumference away from the equator.

http://gea.zvne.fer.hr/module/module_b/module_b3.html

The Equator• This is an imaginary line that divides the globe into equal

hemispheres. • All parallels in the northern hemisphere are designated

as having north latitude.• All parallels in the southern hemisphere are designated

as having southern latitude.

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– Seven significant latitudes

– Fig. 1-13 and 14

Latitude• Regions on Earth are

sometimes described as falling within general bands of latitude.– Low latitude—generally

between the equator and 30ºN and S

– Midlatitude—between about 30-60º N and S

– High latitude—latitudes greater than about 60º N and S

– Equatorial—within a few degrees of the equator

– Tropical—within the tropics (between 23.5º N and 23.5º S)

– Subtropical—slightly polewardof the tropics, generally around 25–30º N and S

– Polar—within a few degrees of the North or South Pole

Nautical Miles

• The actual length of one degree of latitude varies according to where it is being measured on Earth, because of the polar flattening of Earth. Even with the variation, each degree has a north–south length of about 111 kilometers (69 miles).– A nautical mile is defined by the distance

covered by one minute of latitude (1.15 statute miles or 1.85 kilometers).

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Longitude• Longitude—the distance

measured east and west on Earth’s surface.

• Meridian—imaginary line of longitude extending from pole to pole (aligned in a north–south direction), crossing all parallels at right angles. (It’s not to be confused with its other definition, the sun’s highest point of the day.)– Meridians are not parallel to each

other, except where they cross at the equator, where they are also the furthest apart.

– They close together northward and southward, converging at the poles.

Longitude• This is the angular distance

of a point east or west of the prime meridian located at Greenwich, England.

• It increases to the west and the east away from the prime meridian (0°) to a maximum of 180°.

• Lines of longitude are farthest apart at the equator and converge at the poles.

• All circles described by meridians of longitude have the same circumference.

http://gea.zvne.fer.hr/module/module_b/module_b3.html

Longitude

• Prime meridian—the meridian passing through the Royal Observatory at Greenwich, England. Longitude is measured from this meridian both east and west to a maximum of 180°.

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Earth-Sun Relations• The functional

relationship between Earth and the Sun is vital because life on Earth is dependent on solar energy.

Earth Movements• Two basic Earth movements are critical for

continuously changing the geometric perspective between the two:

1. Earth’s daily rotation on its axis;2. Earth’s annual revolution around the Sun.

Earth’s Rotation on Its Axis• Earth rotates toward the east on its axis, with one complete rotation

taking 24 hours.• This eastward spin creates an illusion that the celestial bodies are

rising in the east and setting in the west.• Although the speed of rotation varies from place to place, it is

constant in any given place, so humans do not experience a senseof motion.

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Earth’s Rotation on Its Axis• This rotation has several striking effects on the physical

characteristics of Earth’s surface:– There is an apparent deflection in the flow path of both air and

water; called the Coriolis effect, it deflects to the right in the Northern Hemisphere and to the left in the Southern Hemisphere.

– Any point of the surface will pass through the increasing and decreasing gravitational pull of the Moon and the Sun.

– Most important of all, there is a diurnal (daily) alternation of light and darkness, which in turn influences local temperatures, humidity, and wind movements.

Earth’s Revolution around the Sun

• Tropical year—the time it takes Earth to complete one revolution around the Sun; for practical purposes it can be simplified to 365.25 days.

• Earth’s revolution is an ellipse, which varies the Earth–Sun distance.

Earth’s Revolution around the Sun

• The varying distance between Earth and the Sun is not an important determinant of seasonal temperature fluctuations.– Perihelion—the point in an orbit that takes a planet

nearest to the Sun (for Earth, it is 147,166,480 kilometers or 91,455,000 miles, on January 3).

– Aphelion—the point in an orbit that takes a planet furthest away from the Sun (for Earth, it is 152,171,500 kilometers or 94,555,000 miles, on July 4).

http://esminfo.prenhall.com/science/geoanimations/animations/01_EarthSun_E2.html

ANIMATIONS: animated movie Earth moving around sun showing the seasons

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Inclination of Earth’s Axis• Plane of the ecliptic—the

imaginary plane that passes through the Sun and through every point of Earth’s orbit around the Sun.– It is not perpendicular to

Earth’s rotation axis, which allows for seasons to occur.

• Inclination of Earth’s axis—the degree to which Earth’s rotation axis is tilted (about 23.5˚ away from the perpendicular).

Polarity of Earth’s Axis• Polarity of the rotation

axis—also called parallelism; occurs because Earth’s axis points toward Polaris, the North Star, no matter where Earth is in its orbit.– The combination of

rotation, revolution, inclination, and polarity result in the seasonal patterns experienced on Earth.

The Annual March of the Seasons

• During the year the changing relationship of Earth to the Sun results in variations in day length and in the angle at which the Sun’s rays strike the surface of Earth. – The latitude (or subsolar point or the

declination of the Sun) receiving the vertical rays of the Sun.

– The solar altitude at different latitudes.– The length of day at different latitudes.

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– Figure 1-23: “Top view” of the march of the seasons.

June Solstice

• June Solstice—On or about June 21, the North Pole is oriented most directly toward the Sun.– On this day the direct rays of the Sun at noon

strike perpendicular to the surface of the Tropic of Cancer (23.5º N).

– The day lengths are longer in the Northern Hemisphere on this day, and day lengths are shorter in the Southern Hemisphere.

June Solstice• Day length is equal on the equator because the circle of

illumination (the line dividing between half daylight and nighttime on Earth) bisects the equator evenly.

• Arctic Circle—the parallel of 66.5° north latitude; experiences 24 hours of light on this day.

• Antarctic Circle—the parallel of 66.5° south latitude; experiences 24 hours of darkness on this day.

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September Equinox (AKA autumnal equinox)

• Occurs on or about September 22 and all latitudes experience 12 hours of day and 12 hours of night. This is because all latitudes are bisected evenly by the circle of illumination.

• The equinoxes represent the midpoints in the shifting of direct rays of the Sun between the Tropic of Cancer and the Tropic of Capricorn.

December Solstice• December solstice – On or about December 21,

the South Pole is oriented most directly toward the Sun.– On this day the direct rays of the Sun at noon strike

perpendicular to the surface of the Tropic of Capricorn (23.5º S).

– The day lengths are longer in the Southern Hemisphere on this day, and day lengths are shorter in the Northern Hemisphere.

December Solstice• Day length is equal on

the equator because the circle of illumination (the line dividing between half day light and nighttime on Earth) bisects the equator evenly. – Arctic Circle—the parallel

of 66.5° north latitude; experiences 24 hours of darkness on this day.

– Antarctic Circle—the parallel of 66.5° south latitude; experiences 24 hours of light on this day.

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March Equinox (AKA vernal equinox)

• Occurs on or about March 20 and all latitudes experience 12 hours of day and 12 hours of night.

• This is because all latitudes are bisected evenly by the circle of illumination.

– Figure 1-24: Earth-Sun relations on the solstices and equinoxes.

Seasonal Transitions• Between the March equinox and

the June solstice the vertical rays of the Sun migrate northward until they reach the Tropic of Cancer

• Latitudes north of the Tropic of Cancer never experience the vertical rays of the Sun, so the June solstice marks the day when they are at their highest angle.

• After the June solstice the vertical rays migrate south and the situation is similar in the Southern hemisphere between the September equinox and the December solstice, with the Sun’s vertical rays reaching their farthest point south at the Tropic of Capricorn on December 21.

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Subsolar Point

The latitudeof the subsolar point marks thesun’s declination which changesthroughout the Year.

Day Length

• This shifting of the vertical rays of the Sun has a direct influence on day length.

• Day length for a given hemisphere is longer as the vertical rays of the Sun approach the tropics within that hemisphere.

– Summary of Conditions on Equinoxes and Solstices

– Table 1-6

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Day Length in the Arctic and the Antarctic

• On the March equinox the Sun rises at the North Pole and is continuously above the horizon until the following equinox in September.

• Constant daylight extends southward to the Arctic Circle until the Sun’s vertical rays reach their highest point on June 21.

Day Length in the Arctic and the Antarctic

• Daylight begins to decrease northward toward the North Pole until the September equinox.

• Between the September equinox and the March equinox, the North Pole is in continual darkness.

• This overall pattern is reversed for the Southern Hemisphere with increasing daylight between the South Pole and the Antarctic Circle between the September and the March equinox.

– Variations in Day Length and Sun Angle• June Solstice (example)

– Table 1-7

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Significance of Seasonal Patterns

• Both day length and the angle at which the Sun’s rays strike Earth are principal determinants of the amount of insolation received at any particular latitude. – Tropic latitudes are always warm/hot because

they always have high Sun angles and consistent days close to 12 hours long.

– Polar regions are consistently cold because they always have low sun angles.

Telling Time• It was difficult to compare

time at different localities when transportation was limited to foot, horse, or sailing vessel. – Thus there were no

standard times; each community set its own time by correcting its clocks to high noon (meridian, not to be confused with meridian of longitude).

Standard Time• Use of local solar time

created increasing problems with advent of telegraph and railroad; railroads stimulated development of a standardized time system.– An 1884 international

conference divided world into 24 standard time zones, each extending over 15° of longitude (also determined prime meridian).

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– U.S. Time Zones

– Fig. 1-30

Standard Time• Universal Time Coordinated

(UTC) — formerly Greenwich mean time (GMT); a standardized time system that uses the local solar time of Greenwich (prime) meridian as its standard.

• In international waters, time zone boundaries are defined specifically and consistently;

• Over land areas, however, zone boundaries vary, sometimes undergoing great manipulation for political and economic convenience.

International Date Line

• International Date Line—Along with prime meridian, provides the anchor for the framework of time zones. – It is the line marking

where new days begin and old days exit from surface of Earth.

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International Date Line• Experiences a time

difference of an entire day from one side of the line to the other. – Generally, the line falls on

the 180th meridian except where it meanders to ensure two island groupings aren’t split apart in their schedules (Aleutian Islands and South Pacific Islands).

Different days are observed on either side of the International dateline (180th meridian = 15° X 12 hours), 12 hours difference from the Prime Meridian

International Dateline

International Date Line• The extensive eastern displacement of the

date line in the central Pacific is due to the widely scattered distribution of many of the islands of the country of Kiribati

http://www.flickr.com/photos/telstar/433029904/

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Daylight Saving Time• Daylight Saving Time—

a practice by which clocks are set forward by an hour (or more) so as to extend daylight into the usual evening hours. – Created originally in

Germany to help conserve electricity for lighting.

– Became U.S. national policy, though Arizona, Hawaii, and part of Indiana exempt themselves under the Uniform Time Act.

– Now gaining international acceptance.

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01_T05.JPG

North America Map TermsBrooks RangeRocky MountainsSierra Nevada MountainsCascade MountainsAppalachian MountainsSierra Madre OccidentalSierra Madre OrientalYucatan PeninsulaGreat Plains

Mississippi RiverMissouri RiverColorado RiverRio GrandeColumbia River

Lake SuperiorLake HuronLake MichiganLake ErieLake OntarioLake WinnipegLake OkeechobeeGreat Bear LakeGreat Slave LakeGreat Salt LakeGulf of St. LawrenceLago Nicaraugua