Download Measuring the Earth

Unit 2
Measuring the Earth
Mapping
Size and Shape
 Almost a perfect sphere- slight flattening
in the polar regions and a slight bulging
at the equatorial region.
 Evidence- photos from space, ships
“disappearing” over horizon
 Earth’s circumference is about 40,000
km
Spheres of the Earth
 Series of spheres held together by
gravity, arranged from lowest density to
highest.
- Atmosphere (gas)
- Hydrosphere (liquid)
- Lithosphere (solid)
- Earth’s interior (mostly solid, some
liquid)
Atmosphere
 The atmosphere can be divided into
more spheres.
- Thermosphere (highest)
- Mesosphere
- Stratosphere
- Troposphere (lowest)
Atmosphere
 Composed mainly of nitrogen and
oxygen
 Furthest sphere from the Earth’s center
because it is the least dense.
 The interfaces between layers are
called pauses
Hydrosphere
 Layer of water
 Includes the oceans, (70% of Earth’s
surface) lakes, streams, and rivers.
 Composed mainly of H2O
Lithosphere
 Layer of rock that forms the hard outer
shell of the Earth’s interior.
 100 km thick and lies beneath the
atmosphere and hydrosphere.
 Composed of plates called lithospheric
plates
 Upper portion is called the crust
Earth’s Interior
 Region extending from the rocky part of
the Earth’s crust to the Earth’s center.
Locating Positions on Earth
 To find a location on a two dimensional
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surface you need two numbers or
coordinates.
Coordinate system- system for determining
coordinates.
What is the name of the coordinate system
used to find a location on the Earth’s surface?
Latitude-longitude
Measured in degrees and minutes: 60minutes
In 1 degree.
Latitude
 The angular distance north or south of
the equator.
Latitude con’t.
 These circles are called parallels of
latitude or just parallels
 Latitude increases north and south of
the equator to a maximum of 90
degrees.
 When writing a location with latitude you
must indicate N or S.
Longitude
 The distance east or west of the prime
meridian.
 Meridian- semi circle on the Earth’s surface
connecting the north and south poles.
 Prime Meridian- meridian of zero longitude.
 When writing a location with longitude you
must indicate W or E.
Longitude con’t.
 To read a location on an Earth model
such as a map or globe you need to
locate the coordinates for both
latitude and longitude. Latitude
values can be found on the left and
right sides of the map and longitude
can be found at the top and bottom.
Fields
 Any region of space or the environment
that has some measurable value at
every point.
 Examples: temperature fields, wind
speeds, atmospheric pressure. More?
Example of a Field
Isolines
 Lines on a map that connect points of
equal field values
 Different kinds:
Isotherms- points of equal temperature
Isobars- points of equal air pressure
Contour lines- points of equal elevation
Gradients and Changes in
fields
 Gradient- the rate of change from place to
place within the field
 Gradients can be determined two ways:
- estimate; the closer together the lines, the
greater the gradient
- calculate; gradient = change in field value
-------------------------change in distance
Mapping Earth’s Surface
 Topographic maps (contour map)- maps
that attempt to show the elevation of a
field on the Earth’s surface.
 Some reasons to use a topographic
map:
- Construction site selection
- Hiking or fishing
- Finding natural resources such as water
Reading Contour Lines
 Contour interval- the difference in
elevation between consecutive lines
 Contour interval usually found in key or
legend.
Rules to Follow When
Reading a Contour Map
 When contour lines
 Every 4th or 5th line
cross a stream, they
bend upward. Contour
lines “point” upstream
 When there is a series
of consecutively smaller
and smaller lines, the
elevation is increasing
toward the top of a hill
or mountain.
shows the elevation
 Benchmarks indicate an
exact elevation and are
indicated on a map as
BM X
 Depression lines are
marked with small lines
pointing towards the
center of the
depression.
Contour Map Showing a
Depression
Symbols on Topographic
maps
 There are hundreds of symbols.
 Most government maps use colors:
- red and black: human constructions
- Blue: water
- Green: woods or areas of vegetation
- Purple: where map has been revised
using aerial photographs.
Horizontal Distance on Maps
 Map Scale- a ratio of distance between two
places on a map and the actual distance on
Earth’s surface.
 Can be expressed three ways:
1. Verbally, “one inch equals a mile”
2. Fractionally, 1/500,000 or 1:500,000- this
means any one distance on the map equals
500,000 of the same units on Earth’s surface
3. Graphically, as seen in fig. 2-8 pg. 24
Finding the distance of a
curved line
 How do you measure the distance on a
map of a curved line?
Map Profile
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Profile- side view of an area’s landscape.
Steps to create a profile:
A line X-Y is drawn on the map. Place a
piece of paper along the line.
Mark the paper wherever a contour line
crosses the paper.
Label the marks with the correct elevation.
Place the paper horizontally on a piece of
lined paper. Project the lines upward onto
the paper and mark with a dot when you
reach the corresponding altitude.
Finally the dots are connected using a
curved line.
Map Direction
 Most maps are constructed so the top of
the map is north the bottom is south the
right side is east and the left side is
west.
 Magnetic north is labeled MN.
 What does a compass rose look like?