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GG101 Study Guide - Midterm Guide: Cool Air, Ionosphere, Spheroid

Course Code
Rich Petrone
Study Guide

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Chapter 1
Parallels of Latitude
- equator= largest
- E-W Compass directions
- across axis of rotation
- Latitude = angular distance north or south of the equator, measured from the center of
Sub- dividing Latitude
- 1degree of latitude = 110km of linear distance
- more precision: minutes of arc (represented by ‘)
- 1 minute of latitude= 1/60th of a degree
- 1 minute of latitude ~ 1.83km of linear distance
- MORE precision: seconds of arc (represented by “)
- 1 second of arc is 1/60th of a minute
- one second of arc is about 0.031km, which is very roughly 30m
- Waterloo= lat. 43 degrees 28’ 04”N
Meridians of Longitude
Longitude: is the angular distance East or West of a point on Earths surface, measured
from the center of the Earth
-pole to pole axis rotation
-only half way around the globe
-N-S Compass directions
Great Circles and Small Circles
Great Circle: is any circle that splits the Earth into exactly half, or coincides with the
center of the Earth (ex. Equator)
Small Circle: is any circle that does not coincide with the center of the Earth (meridians)
Map Projections
Mercator projection: most commonly used, is a cylindrical projection
Rhumb line: the line of constant direction or the mercator projection. Is a straight and
thus facilitates plotting directions between two points
4 Classes of Map Projections:
- Cylindrical
- Planar
- Oval
Written Scale: one mm equals 5km
Representative Fraction: 1:250,000 or 1/ 250,000
Graphic Scale:

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Types of Scales:
Small Scale: 1:2,500,000
Medium Scale: 1:125,000
Large Scale: 1:24,000
Earths Rotation
-Planet spins slowly -> rotation= 1 solar day
- Counter- clockwise direction when looking at the North Pole
- Poles= intersections of axis of rotation and earth’s surface (N&S)
Why is it Important?
- convenience for humans
- geographic grid
- influences physical and life processes on Earth
- Environmental Effects of Rotation
- imposes daily or diurnal rhythms
- flow paths of air/water are turned in one direction
- movement of tides
Global Time Zones- Relationships with Longitude
- 15 degrees of longitude= 1hr of time
- International Date Line:
- which marks the place where each day officially begins at 12am
- the day is swept wester ward across the globe, starting at The International
Date Line
World Time Zones
- Standard Time
- divides the globe into 24 time zones
- Daylight Savings Time
- done to maximize daylight period
- International Date Line
- Same calendar day at midnight; any other time= different days
Chapter 2
How Do Earth- Sun Relations Affect Seasonality on Earth
- Seasonality: seasonal variation of:
- 1. Sun’s Position above the horizon
- a) Altitude
- b) Declination
- 2. Changing day lengths

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Perihelion: closest to the sun, January 3, 147,255,000km
Aphelion: Farthest from the sun, July 4, 152,083,000km
Reasons for the Seasons
1. Revolution
2. Rotation
3. Tilt of Earth’s axis
4. Axial Parallelism
5. Sphericity
Orbit around the Sun; requires 365.24 days to complete
at 107,280km
Earth turning on its axis; takes approximately 24 hours
to complete
Axis is aligned at about 23.5 degree angle from a
perpendicular to the plane of the ecliptic (the plane of
earths orbit
Axial Parallelism
Remains in a fixed alignment, with Polaris directly
overhead at the North Pole throughout the year
Appears as an oblate spheroid to the Sun’s parallel
rays; the geoid
Tilt Of Earths Axis
- The earth's axis is tilted not quite 23½° from “the vertical”.
“The vertical”?
"- The plane of reference from which earth is tilted = "plane of ecliptic.” (yellow) - -
- This is the plane of the earth's orbit around the sun.
- Earth is at a 23 ½ degree angle at it moves around the sun –part of the planet points
toward the sun at one point and at the same time, part of the planet is pointing away
from the sun
– consider the alternatives…
- if the earth were tilted on its side with its axis parallel to the plane of the ecliptic we
would see huge variation in seasons worldwide (think about it, half of the earth would be
dark for 6 months).
- if the earth’s axis was perpendicular to the plane of the ecliptic (ie no tilt at all), we
would experience perpetual fall/spring like season, and, all points on planet would get
12 hrs of sunlight
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