Ch01

Chapter 1: Introduction to Earth

McKnight’s Physical Geography: A Landscape Appreciation,

Tenth Edition, Hess

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

2© 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?”


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”


Science and Geography

• Measurement Systems– Need measurement

systems to quantify scientific processes

– SI versus English units– Conversions


The Environmental Spheres

• Four primary spheres1. atmosphere—“air”

2. lithosphere—“stone”

3. hydrosphere—“water”

4. biosphere—“life”

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2 3

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Interactions between the spheres

© 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

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Figure 1-4


The Solar System

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Figure 1-5


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

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

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Figure 1-9


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

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Figure 1-10© 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

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Figure 1-12


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

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Figure 1-16


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


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

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Figure 1-19


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”)

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Figure 1-20


The Annual March of the Seasons

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• Three important conditions– Declination of the Sun

– Solar altitude

– Length of day

• Two solstices– June solstice

– December solstice

• Two equinoxes– March equinox

– September equinoxFigure 1-22



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• 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



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• 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



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• 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



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• 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



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• 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


Telling Time

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• 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


Telling Time

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• 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


Telling Time

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Figure 1-24

• Time zones of the world


Telling Time

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• Time zones of the United States

Figure 1-25


Telling Time

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• 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


Summary

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• 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


Summary

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• 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


Summary

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• 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


Ch01

Documents

pearson education

earth geography

geographic grid earth

shape of earth

earths orbit

gas giants earth

ecliptic earths axis

poles rotation