Transcript The Earth - Valhalla High School

The Earth
Earth’s Shape
• Earth is an oblate
spheroid, slightly
flattened at the
poles and bulging
a little at the
equator
• From outer space,
Earth looks
perfectly round
and smooth
Earth’s Structure
• The Earth has three major parts
– Lithosphere (solid)
– Hydrosphere (liquid)
– Atmosphere (gas)
The Lithosphere
• The dense, solid shell of the earth composed
of rock and soil that surrounds the more fluid
inner layers
The Hydrosphere
• The waters of the earth including the
oceans, lakes, rivers, and water in the
ground
• Covers 70% of the earth’s surface
The Atmosphere
• The shell of gasses that surround the earth
and is layered into zones
– Troposphere contains the
gasses necessary for life
• 78% nitrogen, 21% oxygen,
1% other gasses
• Strong winds and storms along
with most of the water vapor
and clouds
– Stratosphere
– Mesosphere
– Thermosphere
Earth’s Magnetic Field
• Our planet has a magnetic field as if a giant
bar magnet were buried within Earth.
• When you use a
magnetic compass,
the compass
needle points
toward Earth’s
magnetic pole
that is very close
to the geographic
north pole.
Locating Positions on Earth
• Coordinate System
– Scientists have established a surface grid (lines)
that you can use to locate any position on Earth.
– Each pair of coordinates (2 numbers) are called
the latitude and longitude
• Latitude are distances in degrees north or south of
the equator
– The Equator is an imaginary line that circles the Earth
halfway between the North Pole and the South Pole.
• Longitude are distances in degrees east or west of
the prime meridian
– The Prime Meridian is an imaginary line that runs through
Greenwich, England, from the North Pole to the South Pole
Coordinate System
Navigation
• The science of locating your position
on Earth
• Any location north of the equator has a
latitude that is equal to the angle of
Polaris (the North Star’s altitude)
above the horizon
Finding the North Star Polaris
Navigation
Finding the Altitude of a Star
• The altitude is the
angular height
above the horizon
• Measurement can
be made using an
astrolabe
– A protractor with a
heavy weight
suspended
Solar Time and Clock Time
• Clock time is based on observations
of the sun
• Noon is the time
when the sun
reaches its
highest point
in the sky
Calculating Longitude
1. Find the difference between local clock
time and Greenwich time
2. Multiply this time difference by 15° per
hour
3. If local time is earlier than Greenwich
time, your position is West of the prime
meridian or West Longitude
4. If local time is later than Greenwich time,
your position is east of the prime
meridian or East Longitude
Fields
• A region of space where every point or
location can be measured
• Isolines connect points of equal values
on a field map
• Isotherms connect points of equal
temperatures
• Isobars connect points of equal air
pressure
• Contour lines connect point of equal
elevation
Field Maps
The numbers on the map represent
the concentration of gasoline found
at that location. So the map simply
shows how much of something (in
this case gasoline) is found at many
locations.
This map has all of the
isolines drawn in, at an interval
of 10 (each line is 10 units
apart)
Topographic Map (Contour Map)
• Show the shape of the
Earth’s Surface
• Contour lines drawn
on a map give the
elevations for a region
• Where the lines are
close, the slope of the
ground is steep
• Where the lines are far
apart, the slope of the
ground is gentle
Contour Map Example
On this map, the vertical distance between each of the contour lines is 10 feet.
1. Which hill is higher,
hill A or hill B?
2. Which hill is steeper,
hill A or hill B?
3. How many feet of elevation
are there between contour
lines?
4. How high is hill A? Hill B?
5. Are the contour lines closer
on hill A or hill B?
Topographic Profile
• A cross sectional view that shows the
elevation of the land
Determining Gradient and Slope
• The rate of change in field values between
two points in a field
• The average slope, or gradient, between
any two points (A and B) on a mountain can
be determined from a contour map
Difference between A and B
Gradient =
Distance between A and B
Determining Gradient
Sample Problem
• Calculate the average slope of a mountain trail from the
980-meter contour line to the 480-meter contour.
• The distance between these two elevations measures 4
kilometers.
Gradient =
Difference in elevation (m)
Distance between the points (km)
= 980 m – 480 m
4 km
= 500 m
4 km
= 125 m/km