Models of the Earth

Chapter 3

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Geographic North Pole and South Pole - the points at which Earth’s axis of rotation intersects Earth’s surface

Used as reference points for defining direction.

Equator - halfway between the poles, divides Earth into the North and South Hemispheres.

A reference grid that is made up of additional circles is used to locate places on Earth‘s surface.

parallel - any circle that runs east and west around Earth and that is parallel to the equator; a line of latitude

latitude - the angular distance north or south from the equator; expressed in degreesthe equator is 0° latitudeThe latitude of both the North Pole and

the South Pole is 90°1° latitude equals about 111 km

Parallels of the Earth

Minutes and Seconds

Minutes - Each degree of latitude consists of 60 equal parts, called. One minute (°) of latitude equals 1.85 km

Seconds - each minute is divided into 60 equal parts (°)

Meridian - any semicircle that runs north and south around Earth from the geographic North Pole to the geographic South Pole; establishes East-west locations

Longitude - the angular distance east or west from the prime meridian; expressed in degrees Distance covered by a degree of longitude

depends on where the degree is measured Decreases as you move from the equator

toward the poles.

Prime meridian -passes through Greenwich, England represents 0° longitude.

International Date Line - The meridian opposite the prime meridian, halfway around the world, is labeled 180°

Great circle - any circle that divides the globe into halves; marks the circumference of the globe Any circle formed by two meridians of

longitude that are directly across the globe from each other

The equator is the only line of latitude that is a great circle.

The route along a great circle is the shortest distance between two points on a sphere.

Great circles are commonly used in navigation, Ex. air and sea routes

magnetic compass - used to find direction on Earth

Geomagnetic poles - areas on Earth’s surface just above the poles of the imaginary magnet

The geomagnetic poles and the geographic poles are located in different places.

Magnetic declination - angle between the direction of the geographic pole and the direction in which the compass needle points In the Northern Hemisphere, magnetic

declination is measured in degrees east or west of the geographic North Pole.

Earth’s magnetic field is constantly changing, as is the magnetic declinations of locations around the globe

By using magnetic declination, a person can use a compass to determine geographic north for any place on Earth

GPS (global positioning system) - another way people can find their location on Earth A satellite navigation system that is

based on a global network of 24 satellites that transmit radio signals to Earth’s surface

A receiver held by a person on the ground receives signals from three satellites to calculate the latitude, longitude, and altitude of the receiver on Earth

Topographic Map SymbolsSymbols are used to show certain features

on topographic maps.

Symbol color indicates the type of feature Constructed features - black Highways - red Bodies of water - blue, Forested areas - green.Contour lines - brown or black

Geologic maps Show geologic features

types of rocks found locations of faults, folds, and other structures

Rock Units on Geologic Maps Geologic units are distinguished by color. Units of

similar ages are generally assigned colors in the same color family, ex. different shades of blue.

Letters are assigned to each rock unit symbolizes the age of the rock and the name of

the unit or the type of rock

Contact line Other markings on geologic maps Contacts - indicates places at which two geologic

units meet faults depositional contacts

Geologic maps also indicate the strike and slip of rock beds.

Strike - indicates the direction in which the beds run,

slip - indicates the angle at which the beds tilt.

Uses of soil maps: classifymapdescribe soils, based on surveys of soils in a

given area.

3 main parts of soil surveys: text, maps tables.

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

Tables - describe the types and volumes of soils in the area.

Maps - show the approximate locations and types of the different soils.

Valuable tools for agriculture and land management.

Used by farmers, agricultural engineers, and government agencies.

The information in soil maps and soil surveys helps developers and agencies identify ways to conserve and use soil and plan sites for future development.

Maps are useful to every branch of Earth science.

Maps that are only one useful type of map.

Benefits of using maps: show the location and flow of water and airstudy changes in Earth’s surface over timeshow topography and rock and soil types