Models of the Earth

Earth Very nearly perfect sphere

No top, bottom or sides Earth’s axis of rotation can be used to

establish reference points Reference points:

North and South poles Equator divides earth into northern and

southern hemisphere

Latitude Parallels-

describes north and south of the equator

Run east-west parallel of the equator

Latitude Angular north or

south of the equator

Degrees of Latitude Measured in degrees Equator is 0° North Pole and South Pole is 90° Each degree consists of 60 equal parts called minutes 1.85 km Symbol is ‘

Each minute is divided into 60 equal parts called seconds Symbol is ‘’

Longitude Meridian

is a semicircle that runs from pole to pole

Prime meridian is 0° Longitude-

is the angular distance east or west of the prime meridian

Degrees of Longitude All locations have a longitude between

0° and 180° east or west of the prime meridian

A degree of longitude equals approximately 111 km Decreases as you move towards the pole

Great Circle Any circle that divides the glove into

halves or marks the circumference of the globe Any circle formed by two meridians of

longitude that are directly across the globe from each other is a great circle

Can run in any direction around the globe Air and sea routes often follow great

circles

Finding Direction Use a magnetic

compass Geomagnetic poles-

areas of earth’s surface above where the poles of the imaginary magnet

Needles of compass points to geomagnetic north pole

Magnetic Declination Angle between the direction of the

geographic pole and the direction in which the compass needle points is called magnetic declination.

Measured in degrees east or west of the geographic north pole

GPS (Global Positioning System) GPS can be used to find their location on

earth Based on a global network of 24

satellites that transmit radio signals to Earth’s surface.

First one was NAVSTAR (launched in 1978)

Can be accurate within 10-15 meters of position

Mapping Earth’s Surface

Mapping Globe- model of earth

Accurately represent locations, relative areas, and relative shapes

Useful for large surface features Too small to show details of earth’s

surface

Making maps Cartography

Scientists who make maps Collect data by a field survey or remote

sensing Remote sensing

The process of gathering and analyzing information about an object without physically being in touch with the object

Map projections Map is a flat representation of Earth’s

curved surface Area may be distorted in size, shape,

distance or direction Map of a city shows slight distortion Map of earth shows greatest distortion

Map projection A flat map that represents a spherical

surface

Cylindrical Projections Meridians appear as

straight, parallel lines that have an equal amount of space between them

Advantage: Parallels and

meridians form a grid (locating positions is easier)

Azimuthal Projections Place a sheet of paper

against a transparent, lighted globe so that paper touches the globe at only one point

Great for air travel and finding great circles

Little distortion at point of contact

Unequal spacing between parallels causes distortion in both direction and distance

Conic Projections Made by placing a paper

cone over a lighted globe so that the axis of the cone aligns with the axis of a globe.

Touches the globe at a parallel

Where the cone and globe are in contact have the slightest distortion

Reading a Map North on top, east on the right, south on

the bottom, west on the left Never Eat Soggy Waffles

Parallels run from side to side Meridians run from top to bottom Legend- a list of map symbols and their

meanings

Map Scales Scale- the relationship between the distance

shown on a map and the actual distance Graphic Scale- Printed line that has markings

on it that are similar to those on a ruler Fractional Scale- 1:25,000 (one unit of

distance represents 25,000 of the same unit on earth

Verbal Scale- Sentence form (One cm is equal to one km)

Isograms A line on a map

that represents a constant or equal value of a given quantity

Meteorologists use to show atmospheric pressure

Types of Maps

Topographic Maps The size and shape

of the land surface features of a region including its relief

Natural features Shows elevation

The height of an object above sea level

Topographic Maps More detailed information about the

surface Shows size, shape and elevation Contour lines- a line that connects

points of equal elevation on a map (is an isogram)

Relief- the difference between the highest and lowest elevations in a given area

Topographic Maps Widely spaced contour lines indicate

gradual change in elevation Closely spaced contour lines is a rapid

change in elevation Contour lines that bend to form a V is a

valley Closed loop contour lines indicate a

hilltop

Topographic Maps Buildings, boundaries, roads, and

railroads- normally in black Major highways-red Bodies of water-blue Forest-green Contour lines- brown and black

Geologic Maps Show distribution

of geologic features

Types of rocks, locations of faults, folds, etc.

Geologic Maps Geologic unit- volume of rock of a given

age range and rock type Assigned by color Letters represent age

One capital letter- symbolizes age of rock Lowercase letters- represent the name of

the unit or type of rock

Geologic Maps Contact lines-indicates places at which two

geologic meet Strikes-indicates direction in which beds run Dips- Indicates the angle at which the beds

tilt Two types of contacts

Faults- cracks where rocks can move past each other

Depositional contacts-show where one rock layer formed above another

Soil Maps Classify, map and

describe soils Based on soil

surveys NRCS (Natural

Resources Conservation Service maps soil

Soil Maps Soil Survey

Text- general information about the geology, topography and climate of area being mapped

Tables- describes and volumes of soils in the area Maps-

General map shows the approximate location of different types of soil within the area

Detailed information about soils Uses- agricultural and land management