Physical Geology Interactive: The Lab

Goals

	Introduce longitude and latitude
	Describe the components of a map
	Show how spatial data are represented on contour maps
	Introduce the contour profile
	Explain the tier and range system

Introduction

Maps are important to everyone.

City maps help delivery

companies get packages to us.

We follow highway maps

across the country.

Aeronautical charts guide airline

pilots around the world.

Hikers, hunters, and foresters

visualize the surface of

the land using topographic maps.

Although map making began

centuries ago, maps are even

more important in today’s technological

society. Land ownership must

be precisely recorded,

flood-prone areas identified,

productive agricultural land surveyed,

and the spread of disease documented.

Because they represent the

Earth’s surface,

maps cannot convey

all the information

about the surface.

Some data must be

omitted and other data

generalized to keep the

map from becoming too cluttered.

A map’s purpose(s) determines

what information is included.

For example, water

ownership maps would show

streams and lakes

but probably omit

information about geology.

Not including some details

produces a clear

map that highlights

the information it

was created to show.

A mapmaker also must

decide how accurately to

represent global surface

features. A highway map of

Maine may depict the

seacoast with less detail

than the highways,

whereas a navigational

chart will show the

shoreline in great detail

but might omit information

about coastal roads.

Maps are used to

accomplish three goals:

Locate places
Show distribution patterns
Compare and contrast information

Some of the types

of data portrayed

on maps include

Political: countries, states or provinces, or cities
Physical: mountains, rivers, continents, oceans, lakes, and streams
Road: roads, railroads, airports, and ports
Thematic: any information that varies spatially, such as soil types, Earth resources, and water sources
Weather: cold fronts, storm centers, and types and amounts of precipitation

Various types of maps

can be combined.

For example,

a political thematic map

might show the

distribution of population,

land ownership, or

other man-made features.

Although positional data

should not change with time,

other information portrayed

on a map may have a

limited period of use.

Political maps may be

accurate for decades or

perhaps for only several years.

Weather maps are

useful for only a few hours.

Geologic maps should

remain useful for many years.