Regents Earth Science
Chapter 1 “Planet Earth”
Class Notes
Earth’s Shape
Nearly a perfect sphere
 Slightly flattened at the poles
 Slightly bulging at the equator
 AKA Oblate Spheroid
Proof of Earth’s shape:
 Ships “sink” below the horizon
 Force of gravity nearly equal at any point on Earth’s surface
 Sun and stars appear to be in different positions when viewed at the same time
from different positions on Earth
 During a lunar eclipse, Earth’s shadow on the moon is round
 Satellite photographs indicate Earth is a globe
Location
Poles
Equator
Diameter (km)
12,714
12,756
Circumference (km)
40,008
40,076
Structure of Earth
The outer portion of earth is generally divided into three major parts:
1. Lithosphere(solid)
2. Hydrosphere(liquid)
3. Atmosphere(gas)
Lithosphere:
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Hydrosphere:
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Rigid outer surface of the Earth
Varies in thickness but is approx. 100 km thick
Oxygen and silicon are most common elements found in minerals and rocks
Earth’s liquid water
o oceans
o lakes
o rivers
o groundwater, etc.
Averages depth of 3-5 km
Cover 70% of Earth’s surface
Atmosphere
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Shell of gases that surround Earth
Made of several main layers
Each layer ends in “sphere” while upper boundary of each ends in “pause”
Made of four main layers:
o Troposphere
 Extends to a height of about 12 km above Earth
 Most dense
 Has most mass of four layers
 Made mostly of nitrogen and oxygen
 Most clouds found here
 Temperature steadily decreases here
o Stratosphere
 Contains ozone layer
 Less dense than troposphere
 Temperature steadily increases here
o Mesosphere
 Less dense than the stratosphere
 Temperature steadily decreases here
o Thermosphere
 Least dense layer
 Temperature steadily increase for the first 600 km
 Gradually changes into “outer space” which is a vacuum
Locating Positions on Earth
Mapmakers assign a pair of coordinates called latitude and longitude for every position on Earth
Latitude
 Angular distance in degrees north or south of the equator
 The equator is an imaginary line that circles Earth halfway between the North and South
Pole
 The equator has a latitude of 0°
 Each line of latitude is referred to as a parallel because it is parallel to the equator
 Highest degrees of latitude are 90° N at the North Pole and 90° S at the South Pole
 The position of Polaris can be used to determine latitude from the northern hemisphere
 Other stars must be used to determine position in the southern hemisphere
Longitude
 Does not use a “natural location” to begin measure
 Uses the Prime Meridian as its beginning measure
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Prime Meridian is an imaginary line that runs from the North Pole through
Greenwich, England and continues on to the South Pole
Lines of longitude are measured in degrees east or west of the Prime Meridian
The Prime Meridian has a longitude of 0°
Each line of longitude is referred to as a meridian
The highest degree of longitude is the 180° meridian
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The “International Dateline” follows the 180° meridian
Locations west of the Prime Meridian are marked by degrees west
Locations east of the Prime Meridian are marked by degrees east
Terrestrial Navigation
Navigation:
The science of identifying your position on earth using
Latitude (degrees north or south of the equator) and
Longitude (degrees east or west of the prime meridian)
Latitude North of the equator = angle of Polaris above the horizon
Astrolabes:
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Instrument used to measure the angular altitude of an object in the sky
Looks similar to a protractor with a suspended weight that hangs from a string
Weight hangs straight down to Earth’s center
The string marks the angle of the star above the horizon
Earth’s Magnetic Field
An invisible magnetic field surrounds every magnet
Earth’s magnetic field appears as though there is an invisible bar magnet inside the
Earth
Earth’s magnetic poles are approximately 12° different than the geographic poles
located on
Earth’s spin axis.
Time:
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Can be used to calculate longitude
You need to know your present local time
You need to know present time along the
Prime Meridian (Greenwich Mean Time)
If your time is earlier than GMT you are west
of the Prime Meridian
If your time is later than GMT you are east
of the Prime Meridian
How can you calculate longitude?
1. Find the time difference between your location and that at
Greenwich(GMT)
2. Multiply the difference by 15° per hour
3. The product is equal to your longitude
Example:
It is 9:45 AM in Chicago.
Greenwich Mean Time is 3:45 PM.
There is a 6 hour time difference.
6 x 15 = 90
Chicago time is earlier than GMT.
Chicago is located at 90 °W longitude
Using Scale:
Scale is the ratio of linear dimensions between a model and a real object.
Physical models are made to scale.
Example:
What is the height of this building if the scale used is
1 cm = 3.5 m and the height of the model is 20 cm ?
Use the formula:
Scale Length
= Length of model
Actual Length Length of Object
1 cm =
3.5cm
20 cm
n
n = 3.5 x 20
n = 70 m
Fields: A field is a region in which a similar quantity can be measured at every point or
location. Examples of fields could be the temperature in a room or the elevation of an area.
Isolines: Lines on a field map that connect points of equal value.
Isotherms: Isolines that connect points of equal temperature.
Isobars: Isolines that connect points of equal air pressure.
Contour Lines: Isolines that connect points of equal elevation.
Topographic Maps:
These maps show the shape of Earth’s surface.
Topographic maps are also known as contour maps.
In a contour map, each contour line is separated from the next contour line by a contour
interval.
Contour Interval:
Difference in elevation between two adjacent contour lines.
Contour intervals do not measure distance between two lines on a map. To find
distance you would refer to the scale.
Common Symbols Found on a Topographic Contour Map:
1. Index ContoursUsed to mark elevation on contour maps.
These darker lines may appear every fifth contour line or so.
2. V –
These V marks appear where contour lines cross streams.
The point of the V always points upstream.
Water flows in the opposite direction.
3. Slope (Gradient)Slope is gentle where contour interval is thicker.
Slope is steeper where contour intervals are very narrow.
4. Closed Curve (Circle or oval)Used to mark the area with the highest elevation on a map.
5. Hachure Marks on a Closed CurveThese marks indicate a closed depression which might be an inactive volcano.
Another example of a contour map: