Transcript Chapter 1 - U

Chapter 1
The Earth as a
Rotating Planet
The Shape of the Earth
Earth or Sun moving?
Early sailors view……
Is the Earth a perfect sphere?
(Quasi-sphere)*—Rotation causes it to
bulge at the Equator and flatten at the
Poles *Oblate Spheroid
Earth Rotation
What is rotation?
What direction does the Earth rotate?
How long does it take to rotate?
3 main effects of rotation
Why is rotation important?
Axis serves as reference for geographic grid
(latitude and longitude)
Measure for time (time zones)
Affects physical and life processes
Earth Rotation
Figure 1.2 (P. 26)
The Geographic Grid
What is a geographic grid?
A system for locating or determining the location
of places on the Earth’s surface
Demarcations for hemispheres
Latitude-Distance N or S of the Equator (0
degrees latitude) **Parallels
Tucson is approximately 30 degrees North
Longitude-Distance E or W of the Prime
Meridian (0 degrees longitude)
A few more points about the
latitude and longitude...
Location of a point is given as:
latitude (in degrees N or S), longitude (in
degrees E or W)
There are two techniques for indicating
a more detailed location:
Decimal degrees: 32.13°
Degrees, minutes, seconds: 32° 07’ 48”
Determining a location with
latitude and longitude
Parallels and Meridians
Examples
What city is located at 37°S and 144°E?
Melbourne, Australia
What city is located at 40°N and 105°W?
Denver, CO
What city is located at 51°N and 0°W?
London, England
Distances: Given the fact that the circumference of
the Earth is 24,860 miles and there are 360° in a
circle—How many miles are there in 1 ° of longitude
at the Equator?
Calculating Distances between Lines
of Latitude
Latitude=(69 miles) x (difference in degrees
latitude)
Example 1: Calculate the number of miles
between Atlanta (33°N, 84°W) and New York
City (40°N, 74°W).
Latitude=(69) x (7°)=483 miles
Example 2: Calculate the number of miles
between Prague (50°N, 14°E) and Tripoli,
Libya (32°N, 13°E).
Latitude=(69) x (18°)=1,242 miles
Calculating Distances between Lines
of Longitude (**Difficult)
Longitude=(69 miles) x (COS of parallel
traveled) x (difference in degrees long.)
Example 1: Calculate the number of
miles between Cairo, Egypt (30°N,
31°E) and New Delhi, India (28°N,
77°E). Assume travel along the 29°N
parallel.
Longitude=(69) x (COS 29) x (46°)=2,777
miles
Map Projections
A map is just an abstraction or
representation of the real world. The art
and science of map-making is called
cartography.
When you are trying to represent a
curved surface on flat paper, you get
distortion. Why?
Map units
From Earth to a map
Start with ellipsoid
Difficult, if not
impossible, to take a
curved surface and
place it on a flat
surface
Result is distortion
All maps have some
type of distortion
Five Types of Distortion +1 more
Type
Shape
Scale
Area
Distance
Direction
Example
Circle becomes oval
Map scale changes
Land mass gets bigger
Space between cities
increases
Line varies: N to NW
Polar Projection
Characteristics: a circular
map centered on North or
South Poles and usually
showing one hemisphere
at most; meridians are
straight lines; parallels are
circles
Advantage: Preserves
shapes
Disadvantages: scale and
area distortion
Mercator Projection
A type of conformal projection
Characteristics: rectangular;
meridians and parallels are
both straight lines
Advantage: straight line drawn
on map represents a constant
compass direction
Disadvantages: scale, area,
and distance distortion
Goode Projection
A type of equal-area
projection
Characteristics: odd
shape; meridians both
straight and curved lines;
parallels are straight lines
Advantage: Preserves
area
Disadvantage: shape
distortion
Global Time
How many world time zones? US?
Not exact…why?
Solar noon: period when Sun appears to be highest
in the sky
Lines of longitude used for time zones
15° of longitude = 1 hr of time (360° in one rotation
÷ 24 hrs = 15° per hour)
Example 1: If it is 1 a.m. in Washington D.C., what
time is it in Honolulu, Hawaii?
8 p.m
Example 2: If it is Noon in Charlotte, NC, what time
is it in Madrid, Spain?
6 p.m.
U.S. time zones
Time zones
Global Time (cont’d)
International Date Line
Located approximately along 180°
Why? 180° ÷ 15° per hr = 12 hr. So if it’s 1pm on
the Prime Meridian, the IDL is 1am (next day).
West adds a day
East subtract a day
Daylight Savings Time
Midnight Meridian—the meridian that is
experiencing midnight (the midnight meridian
is NOT stationary)
Time Examples
If it is 10 a.m. in Santiago, Chile on
Tuesday, May 25, what is the time and
date in Taipei, Taiwan?
10 p.m. the same day
If it is 1 p.m. in Juneau, Alaska on
Saturday, June 12, what is the time and
date in Tokyo, Japan?
7 a.m. the next day (June 13)
Longitudnal Time Problems
Example 1: If you depart Washington D.C. (33°N,
77°W) at Noon, at what speed would you have to
travel to arrive in Denver, CO (39°N, 105°W) at
Noon? Assume travel along the 35°N parallel.
Miles=(69) x (COS 35) x (28°)=1,582 miles
1,582 miles / 2 = 791 mph
Example 2: If you depart Philadelphia, PA (40°N,
75°W) at 1 p.m., at what speed would you have to
travel to arrive in Seattle, WA (48°N, 122°W) at 2
p.m.? Assume travel along the 45°N parallel.
Miles=(69) x (COS 45) x (47°)=2,293 miles
2,293 miles / 4 = 573 mph
Earth’s Revolution
Movement of the Earth around the Sun
Counterclockwise if viewed from above
One revolution = 365.242 days = 1 yr
Responsible for:
Seasons
Amount of daylight (along with Earth’s tilt)
Earth’s Revolution (cont’d)
When viewed from above, notice that path of
Earth is not a perfect circle, but an ellipse or
oval.
Perihelion:
When Earth is closest to the Sun
Occurs in January (Northern Hemisphere winter)
Aphelion:
When Earth is farthest from the Sun
Occurs in July (Northern Hemisphere summer)
Earth’s Revolution
Earth’s Revolution (cont’d)
Along with perihelion and aphelion, other
times in revolution also have specific names:
equinoxes and solstices.
Equinoxes
March (vernal) and September (autumnal)
Sun’s rays hit equator at 90° (subsolar pt.)
All latitudes receive ~12 hrs of daylight
Circle of illumination from North Pole to South
Pole
Solstices
Occur in June (summer) and December (winter)
Subsolar point in June: Tropic of Cancer (23.5°N); in Dec:
Tropic of Capricorn (23.5°S)
June solstice: areas from 66.5°N to North Pole receive 24
hrs of daylight (movie – “Insomnia”)
Winter solstice: areas from 66.5°S to South Pole receive 24
hrs of daylight