Transcript Topic 2 Measuring the Earth

Mapping
Topic 2
Measuring the Earth
• The Earth is not a perfect sphere
but it’s extremely close (an oblate
spheroid)
Layers of the Earth
–Lithosphere (solid rock)
»From cooling magma 5 billion years
ago
–Hydrosphere (liquid water)
»From outgassing within Earth’s
interior and precipitation over millions
of years
–Atmosphere (gas)
»From outgassing within Earth’s
interior
Latitude
Measures points north or south of the Equator
Also called “parallels”
Important lines of latitude
Longitude
Measures points east or west
of the Prime Meridian
Also called “meridians”
All lines of longitude meet at
the poles
Earth’s latitude and longitude coordinate system:
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The North Star - Nature's Compass
The North Star (also called Polaris, polar star and polestar) never changes its place in the
sky. When you face it, you are always facing North.
To find the North Star, first find the Big Dipper. Draw a straight line through the two pointer
stars that make up the end of the dipper's bowl and continue this line away from the
opening of the bowl until it intersects with Polaris.
Latitude is determined by the altitude of Polaris (the
North Star)
In the Northern
Hemisphere, the altitude
of Polaris is equal to your
latitude!
Longitude is determined by the apparent position of
the Sun due to Earth’s rotation
Earth rotates 360 degrees in 24 hours (15 degrees per
hour), so every 15 degrees of longitude equals one
hour difference in time.
Because the Earth rotates from west to east, places
to the east see the Sun first and are therefore ahead
on the clock.
World Time Zones
The International Dateline (at 180 longitude) marks the
place where a new calendar day begins
Contour maps (Topographic maps) are used to show elevation of the land
Rules for Drawing Isolines
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1. Every point on an isoline represents an equal value
2. Isolines are generally smooth lines (no sharp corners)
3. Isolines are generally parallel to each other
4. An isoline is an endless line; it either closes upon itself
on the map (forming a circle) or somewhere off the map
• 5. Closely spaced isolines represent steep
gradients/slopes; widely spaced isolines represent gentle
gradients/slopes
• 6. Isolines never branch or fork
• 7. Isolines never cross each other
Special Isolines:
Isotherms connect equal temperatures
Isobars connect equal pressures
Contour lines connect equal elevations
Depressions are shown with hachured contour lines