1. McKnight's Physical Geography 11e
Lectures
Chapter 1
Introduction to Earth
Andrew Mercer
Mississippi State University
© 2014 Pearson Education, Inc.

2. Learning Goals of This Chapter
Distinguish the key concerns for geographers who study the world.
Analyze how geographers use science to explain and understand the natural environment.
Identify the four environmental “spheres” of Earth.
Illustrate how the concept of Earth systems helps us to understand the interrelationships of the four environmental “spheres” of Earth.
Describe Earth’s relationships within the solar system.
Compare the size of Earth with the size of its surface features.

3. Learning Goals of This Chapter
Determine the latitude of a location on Earth.
Determine the longitude of a location on Earth.
Locate a place given the latitude and longitude coordinates.
Explain how latitude and longitude together identify a location on Earth.
Summarize the factors that cause the annual change of seasons.
Describe the changes in the patterns of sunlight around Earth during the year.
Explain how time zones were established.

4. Learning Goals of This Chapter
Describe how time zones are used to establish actual times around the world.
Discuss the relationship between time zones and the international dateline.

5. Introduction to Earth
Geography and Science
Environmental Spheres and Earth Systems
Earth and the Solar System
The Geographic Grid – Latitude and Longitude
Earth–Sun Relations and the Seasons
Telling Time

6. Geography and Science “GEO”-”GRAPHY” Adjective to denote sub-field
Location & Distribution
Physical/Human

7. Establishment of scientific theory
Geography and Science
The scientific method
Observe phenomena
Formulate a hypothesis
Design an experiment to test the hypothesis
Predict the outcome of the experiment
Conduct the experiment
Draw conclusions
Scientific “proof”
Establishment of scientific theory

8. Geography and Science Measurement systems
Need measurement systems to quantify scientific processes
SI versus English units
Conversions

9. Geography and Science
Unit conversions

10. The Environmental Spheres
Four primary spheres
Lithosphere – “stone”
Atmosphere – “air”
Hydrosphere – “water”
Biosphere – “life” 2 3 1 4
Interactions between
the spheres

11. The Environmental Spheres
Earth systems
Closed systems – those contained from outside influence
Open systems – energy and matter free to be exchanged across systems
Equilibrium – systems are in balance (input = output)
Interconnected systems – change in one system affects another (example of a glacier)
Feedback loops, positive versus negative

12. The Environmental Spheres
Positive feedback is a process in which the effects of a small disturbance on a system include an increase in the magnitude of the perturbation.
That is, A produces more of B which in turn produces more of A.
In contrast, a system in which the results of a change act to reduce or counteract it has negative feedback

13. Earth and the Solar System
Earth’s physical characteristics
Maximum relief
See figure
Imperfect sphere
Equatorial diameter ~ 12,756 km
Polar diameter ~ 12,714 km
Circumference of 40,000 km

14. The Geographic Grid – Latitude and Longitude
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

15. The Geographic Grid – Latitude and Longitude
Great circles
Circles that bisect a sphere and pass through the sphere’s center
Identify the shortest distance between two points on a sphere—great circle distance
Plane of the equator is a great circle
Small circles

16. The Geographic Grid – Latitude and Longitude
Graticule
Latitudes
Angle north or south of the equator
Parallels
Seven important latitudes
Latitude zones

17. Seven important latitudes

18. Latitude zones

19. Latitude zones
If you can't pinpoint which of the four zones you live in, simply google "latitude of the name of your city." Once you have the latitude of your city, you'll know which of the four zones you live in:
Tropics: 0 to 23 degrees (eg. Honolulu, HI: 21 degrees)
Subtropics: 23 to 35 degrees (eg. Atlanta, GA: 33 degrees)
Mid-Latitudes: 35 to 50 degrees (eg. Chicago, IL: 41 degrees)
High Latitudes: 50 to 70 degrees (eg. Anchorage, AK: 61 degrees)

20. The Geographic Grid – Latitude and Longitude
Longitudes
Angular description of east–west direction
Meridians
Important longitudes
Convergence at poles
Location on the graticule based on latitude and longitude

21. Important longitude lines

22. International Date Line

23. Grid system

24. Earth–Sun Relations and the Seasons
Rotation of the Earth
24 hours for one rotation
Circular motion at all latitudes but the poles
Rotation is counter-clockwise relative to the North Pole
Converge at the poles
Diurnal transition from light to darkness (circle of illumination)
Tidal effects from the Moon and Sun
Coriolis force

25. Earth–Sun Relations and the Seasons
Earth’s revolution around Sun
One revolution takes 365 ¼ days
Elliptical orbit
Aphelion (152,100,000 km)
Perihelion (147,100,000 km)
Average distance (149,597,871 km)

26. Earth–Sun Relations and the Seasons
Orbital Properties
Plane of the ecliptic
Earth’s axis tilted at 23.5° relative to ecliptic
Polarity of the Earth’s axis
Parallelism
North Pole always points toward Polaris (“North Star”)
Combined effects contribute to seasons

27. Earth–Sun Relations and the Seasons
Two important conditions
Angle of the sun above the horizon
Length of day – circle of illumination
Two solstices
June solstice
December solstice
Two equinoxes
March equinox
September equinox

28. Earth–Sun Relations and the Seasons

29. Earth-Sun Relations

30. Earth–Sun Relations and the Seasons
June solstice
Occurs on approximately June 22 each year
Sun directly overhead at 23.5° N latitude
Antarctic Circle in 24 hours of darkness, Arctic Circle in 24 hours of daylight
Marks start of summer in Northern Hemisphere; winter in Southern Hemisphere

31. Earth–Sun Relations and the Seasons
December solstice
Occurs on approximately December 22 each year
Sun directly overhead at 23.5° S latitude
Arctic Circle in 24 hours of darkness, Antarctic Circle in 24 hours of daylight
Marks start of winter in Northern Hemisphere; summer in Southern Hemisphere

32. Earth–Sun Relations and the Seasons
Equinoxes
Occur on approximately March 20 and September 22 each year
Day length 12 hours worldwide (“equinox”)
Sun directly overhead at the equator
Latitude receiving vertical rays
Varies between the Tropic of Cancer (June solstice) and Tropic of Capricorn (December solstice)

33. Earth–Sun Relations and the Seasons
Day length
Longest in Northern Hemisphere on June solstice
Opposite in Southern Hemisphere
Arctic and Antarctic day length variations

34. June 21

35. March 20 & Sept 22

36. Dec 21

37. Earth–Sun Relations and 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

38. Telling Time Current time system 24 time zones
Greenwich Mean Time (GMT) (also known as Universal Time Coordinated [UTC]) 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 the International Date Line
a.m. and p.m. ???

39. Telling Time
Time zones of the world

40. This arch that stretches over an autopista indicates the Prime Meridian in Spain.

41. Telling Time
Time zones of the United States

43. Daylight-savings time
Telling Time
Daylight-savings 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

44. Daylight Saving Time

45. 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.

46. Summary
The solar system formed 5 billion years ago and consists of eight planets.
Earth is an imperfect sphere.
A latitude and longitude grid helps 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.

47. Summary
Equinoxes and solstices help identify when a seasonal transition occurs.
Time zones were established to have a uniform global time system.
Daylight-savings time was devised to conserve energy by adding an hour of daylight.