Download Chapter One: Mapping the Earth`s Surface

Chapter One: Planet Earth
 The Earth is ALMOST a perfect sphere. It is actually an oblate spheroid, meaning that it
bulges slightly at the equator and is slightly flattened at the poles.
o Proof: Objects weigh slightly more/less at the poles because you they are slightly
closer/farther from Earth’s core, making the force of gravity stronger/weaker.
 From outer space, the surface appears to be smooth. You CANNOT see the bulge and
mountains and valleys do NOT appear as “bumps”
How do we know the Earth is not flat?
 Ships sailing out to sea appear to “sink” as they travel
around the curve of the Earth (demo on globe)
 There is no “edge”
o Technically you wouldn’t fall off even if there was an
edge – why not? Gravity pulls you towards Earth’s
center.
 Lunar eclipses – our shadow is round! Demo with balloons
and projector
 Pictures from outer space – BEST PROOF!
Earth’s 4 Spheres
Atmosphere – (air) mixture of gases that surrounds Earth. Mostly nitrogen & oxygen.
*Note the troposphere is the bottom layer of the atmosphere.
Hydrosphere – (water) all water on Earth. Includes oceans, lakes, rivers, glaciers, etc.
Lithosphere - (land) Earth’s solid, rocky outer layer. Includes the continents, ocean floor, dirt in
your backyard, etc.
Biosphere – (life) all living things on Earth. These creatures may live in the atmosphere,
hydrosphere, or lithosphere.
Use the “Selected Properties of Earth’s Atmosphere” chart on Reference Table p.14 to answer
the following:
1. Water vapor is found in the troposphere. (what layer of the atmosphere?)
2. The tropopause, mesopause, and stratopause are all boundaries between the layers.
3. The term “interface” means boundary.
4. The thermosphere is the top layer, and the troposphere is the bottom layer.
5. The mesosphere begins at an elevation of 50 km.
6. The lowest temperature shown is -90ºC and it is located on the mesopause.
Latitude
 Latitude – horizontal lines that measure distances north and south of the Equator. (It is
actually the angle north or south of the equator).
 Lines run east and west but measure north and south
 Lines are sometimes called parallels
If you slice the Earth in
half and measure angles
from the center, these
would be our latitude
lines.
Important Latitude Lines:
 Equator - 0 latitude - divides the earth into the Northern and Southern Hemispheres.
 North Pole: 90N latitude
 South Pole: 90S latitude
 Tropic of Cancer: 23.5ºN latitude
 Tropic of Capricorn: 23.5ºS latitude
 Arctic Circle: 66ºN latitude
 Antarctic Circle: 66ºS latitude
Note: 1º can be divided into 60 minutes ( ‘ ), which can be divided into 60 seconds( ’’ ).
Half a degree is 30’
Three quarters of a degree is 45’
A quarter of a degree is 15’
A third of a degree is 20’
 Polaris – the “North Star”, is located almost directly above the North Pole.
To find Polaris use the Big Dipper:
1) Find the 2 stars at the end of the Big Dipper’s bowl.
2) These 2 “pointer” stars point to Polaris
Polaris and the Big Dipper
Or use the Little Dipper:
1) The last star on the Little Dipper’s handle is Polaris
Using Polaris to Find Latitude
RULE: The angle of Polaris above the horizon is equal to your latitude. (only works for
Northern Hemisphere)

Polaris

Polaris
Horizon
Horizon (the ground)
90 angle
Location: The North Pole (90ºN)
42 angle
Location: 42ºN
Why does this only work for the northern hemisphere? Polaris cannot be seen from the
southern hemisphere because of the Earth’s curve.
Important Vocabulary Terms:




Navigation: The science of finding your location on the Earth.
Celestial: “of the sky” Ex: moon, stars, sun, etc.
Celestial Navigation: The science of finding your location using the sun or stars.
Astrolabe: Measures the angle of a star above the horizon.
How can an astrolabe be used for navigation? – you can measure the angle of Polaris above
the horizon, which will tell you your latitude.
An astrolabe pointing to an object 46º above the horizon.
Longitude
 Vertical lines that measure distances (angles) east and west of the Prime Meridian.
 Lines run north and south, but measure east and west.
 Sometimes called “meridians”
This diagram shows longitude lines. If you were
standing at the North or South Pole, why would it
be difficult (and unnecessary) to give your longitude?
All longitude lines meet at the poles (can’t pick one)
 Prime Meridian - 0 Longitude.
o Located in Greenwich, England.
o Divides the Earth into the Eastern and Western Hemispheres.
 Longitude lines include numbers 0 to 180.
 180º is the International Date Line
Why are latitude lines, but not longitude lines, sometimes called “parallels”? longitude lines are
not parallel – they meet at the poles.
Give the latitude and longitude of Ithaca, NY to the nearest 30’ (half degree) 42º 30’N, 76º30’W
Time
 We measure time based on the movements of the sun.
 Solar noon: when the Sun is at it’s highest point for that day
 Greenwich Mean Time: (GMT) the time in Greenwich, England (aka time at Prime
Meridian)
 Zenith: point 90º above your head.
Keep in mind: The sun will never be directly overhead (at the zenith) for an observer in New
York State!! You must live between 23.5N and 23.5S latitude for the Sun to be overhead at
some point during the year.
Using Time to Navigate Longitude
RULE: For every 15 of longitude, there is a one-hour time difference. LLE, LEW
If you know the time in Greenwich, England (Greenwich Mean Time), and your local time, then
you can figure out your longitude.
1. Multiply the number of hours difference in time by 15.
2. If local time is later than GMT, then you are east of the Prime Meridian. (LLE)
3. If local time is earlier than GMT, then you are west of the Prime Meridian. (LEW)
Try these:
a) It is 3:30pm in Greenwich, England and 5:30pm at your location. What is your longitude?
2 hrs x 15 = 30 Local time is later than GMT. Therefore my position is 30E
b) It is 2:00pm in Greenwich, England and 6:00pm at your location. Your longitude is 60ºE
c) It is 5:00pm in Greenwich, England and 3:00pm at your location. Your longitude is 30ºW
Topographic Maps
 Field – any area with a value that you are measuring. You may be measuring
temperature, elevation, air pressure, etc. in that area.
 Scale – relates the distances shown on the map to real-life distances.
 Isolines – lines on a map that connect points of equal value.
Types of Isolines:
 Contour lines – connect points of equal elevation
o Elevation: The height of a location above sea level.
 Ex: Elevation = 0 meters, you are at sea level.
 Elevation = 15 meters, you are 15 meters above sea level.
 Isobars – connect areas of equal pressure
 Isotherms – connect areas of equal temperature
 Contour Interval – the change in field value between each contour line.
A Contour Map
Elevations are shown in
meters.
What is the contour interval for the above field? 10m
If drawn three dimensionally, what would this area look like? A hill
In the diagram to the left, the top picture is a
drawing of what the area represented by the
isoline map (below it) looks like.
This map is showing
isotherms/isobars/contour lines
Assuming the elevations are in meters, the
contour interval is 10 meters
The gradient (change in elevation) is
most/least extreme when the lines are close
together.
When Drawing Isolines:
1. Since isolines connect areas of equal value, they can never cross.
2. Isolines should form a complete loop, unless they run off the map.
 A depression, or sinkhole is symbolized by:
 Gradient – shows how much the values change over a certain area. Ex: how much the
temperature changes over a distance of 2 miles.
Gradient = Change in field value
Distance
The temperature in City A is 35ºC. City B is 10km away, and has a temperature of 40ºC.
Calculate the temperature gradient, remember units and show all work below.
_5ºC_ = 0.5ºC/km
10km
Determining Stream Direction
You will often be shown a stream on a topographic map and be asked which direction it is
flowing in. You can determine this two ways:
1. Study the given contour lines and use them to determine which direction is downhill.
2. Remember the rule: Contour lines make a “V” as they cross the stream. These “V”s
ALWAYS POINT UPSTREAM.
In the first picture, what compass direction is the stream flowing? West
In the second picture, the stream is flowing towards/away from the lake.
Topographic Profiles
Creates a profile, or cross-sectional view of the
land.
Mapping Technology
 GPS – Global Positioning System.
This system uses satellites to
determine the exact latitude, longitude,
and elevation of a given point on the
Earth. It contains 24 satellites in all.
 Satellite Mapping – we can use
satellites to make maps from space.
Ex: Google maps!