Ch.1

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 © 2011 Pearson Education, Inc.

2

Geography as a Field of Learning • Definition – “Earth Description” – Geo = earth

• Many sciences branch from geography • Physical versus cultural • “Why what is where and so what?”

© 2011 Pearson Education, Inc.

3

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”


4

Science and Geography • Measurement Systems – Need measurement systems to quantify scientific processes – SI versus English units – Conversions


5

The Environmental Spheres • Four primary spheres 1.

atmosphere— air around us •

2.

lithosphere— rock and soil, solid part of the earth •

3.

Litho = Stone

2

4

3

hydrosphere— water in all its forms •

4.

1

Atmo = Air

Hydro – water

biosphere— all living things, plants, animals, bacteria, viruses •

Interactions between the spheres

Bio = Life

No part exists independently of the others!


6

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.

7

The Solar System

Figure 1-5


8

The Size and Shape of the Earth • Earth’s Physical Characteristics – Oblate spheroid • Approximate diameter 7900 miles • Bulges at equator, flattened at poles – Equatorial diameter ~ 7926 miles – Polar diameter ~ 7900 miles

• Circumference of 24,900 miles


9

Eratosthenes Measured the circumference of the earth in 247 BCE His circumference 26,700 miles – actual 24,900 miles Used simple geometry and trigonometry!


10

Maximum Relief • Difference in elevation between highest and lowest points on earth • Total difference is 65,233 feet • Top of Mt. Everest 29,035 feet above sea level • Bottom of Mariana Trench 36,198m feet below sea level

If the earth were a basketball, Mt. Everest would be one of the little pimples on the surface! © 2011 Pearson Education, Inc.

11

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 - the grid system © 2011 Pearson Education, Inc.

Figure 1-9

12

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 (arc) Airplane routes are Great Circles

– Circle of illumination - Division between daylight and darkness – Small circles – all others © 2011 Pearson Education, Inc.

Figure 1-10 13

Example of Geographic Grid Each point of earth’s surface has a unique intersection of the grid lines Uses a coordinates system with X and Y axis


14

The Geographic Grid

• Latitudes – Parallels – angle north or south of the equator • ¼ of 360 degrees = 90 degrees • From Equator to Pole

– 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) Know these!! © 2011 Pearson Education, Inc.

Figure 1-12

15

Latitude Zones • Tropics – Hot, wet climate – Between Tropics of Cancer and Capricorn – 23.5 N and 23.5 S, with Equator in the middle

• Mid-Latitudes – Temperate climate – Between Tropic of Cancer and Arctic Circle (N) – Between Tropic of Capricorn and Antarctic Circle (S)

• Polar – Cold, dry climate – North of the Arctic Circle (N) and south of the Antarctic Circle (S)


16

The Geographic Grid • Longitudes – Meridians – Prime Meridian (0° longitude) located at Greenwich, England • Zero Degrees = Prime Meridian • 180 Degrees = International Date Line • ½ of 360 degree circle is 180 degrees

– Measures as angle east or west of the Prime Meridian • Must include “east” or “west” with all longitude lines except 0 degrees (Prime • • Meridian) and 180 degrees (International Date Line) © 2011 Pearson Education, Inc.

Figure 1-16 Converge at the poles Farthest apart at the equator

Longitude Standardized • Prime Meridian = Zero degrees longitude – Goes through Greenwich, England, a suburb of London • Chosen by international conference in 1880s to standardize longitude and time worldwide due to train travel

Height of the British Empire so met at Royal Observatory – made it the starting point for longitude. © 2011 Pearson Education, Inc.

18

Where is Los Angeles? • Format for geographic location – Latitude, Longitude

Los Angeles: 34°N, 118°W GPS reading will be more accurate, down to minutes and seconds!


19


20

Graticule – geographic grid system of latitude and longitude lines


21

Earth-Sun Relations • Rotation of the Earth – 24 hours for one rotation (360 degrees = circle) – Circular motion at all latitudes but the poles – Rotation is counterclockwise relative to the North Pole • Rotates toward the EAST • Reason sun “rises” in the east and “sets” in the west

– Converge at the poles • Poles in light ½ year, darkness ½ year

– Diurnal transition from light to darkness • Circle of Illumination – division between light and darkness

– Tidal effects from the Moon and Sun © 2011 Pearson Education, Inc.

22

• Rotates toward the east • Makes one complete rotation every 24 hours • Tilted at 23.degrees from perpendicular of the Axis of Rotation (orbital plane) • Where is surface rotation speed fastest? Slowest? © 2011 Pearson Education, Inc.

23

Earth-Sun Relations • Earth’s Revolution around Sun – Rotation vs. Revolution – One revolution takes 365 ¼ days – Elliptical orbit – Aphelion – farthest July 4 – Perihelion – closest January 3 • Average distance 1 AU Astronomical Unit = 92,955,806 miles – Round to 93 million miles

Figure 1-19 Earth at perihelion during Northern Hemisphere winter; aphelion during Northern Hemisphere summer


24

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

Figure 1-20

» Parallelism (polarity) – earth does not “wobble” on its axis » North Pole always points toward Polaris (“North Star”) © 2011 Pearson Education, Inc.

25

The Annual March of the Seasons • Three important conditions – Declination of the Sun • Where sun is shining 90° to surface – direct sun

– Solar altitude (angle) – Length of day

• Two solstices – June solstice – December solstice

• Two equinoxes – March equinox – September equinox© 2011 Pearson Education, Inc.

Figure 1-22 26

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 © 2011 Pearson Education, Inc.

Figure 1-22

27

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 © 2011 Pearson Education, Inc.

Figure 1-22

28

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


29

file:///C:/Users/Marla%20Conti/Documents/ LastToshiba2013/Geography%20101%20B asics/Old%20McKnight%20Book/Chapter_ 01/animations/01-1_EarthSun.html


30

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.

31

The Annual March of the Seasons • Significance of seasonal patterns – Spread of solar rays over small and large areas • Direct sun = smaller area, more concentrated

– Tropical latitudes consistently warmer • High sun angle, always long days

– Polar latitudes consistently cooler • Low sun angle, some days sun never rises

– Large seasonal variations in temperature in midlatitudes • Many factors, lots of seasonal changes in sun angle, day length, and location of declination (direct sun) – Winter – declination of the sun is in opposite hemisphere © 2011 Pearson Education, Inc.

32


33


34

Telling Time • Three physical measures of time – Tropical year - seasons – Lunar month – new moon – Solar day – noon to noon, sun at highest position in the sky

• Solar noon – Sun casts the shortest shadow – Pre-modern people used this for time, so all towns were different • Ante-meridian (AM—“before noon”) • Post-meridian (PM—“after noon”) © 2011 Pearson Education, Inc.

Figure 1-23

35

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


36

Telling Time • Time zones of the world

Figure 1-24 © 2011 Pearson Education, Inc.

37

Telling Time • Time zones of the United States

Figure 1-25 © 2011 Pearson Education, Inc.

38

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


39

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.

40

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


41

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


42