Download Planet Earth Notes

PLANET EARTH
FYI – This packet and
others like them this
year will be referred to
as your “notes”
“Earth’s Dimensions”
I.
Earth’s Formation
According to the currently accepted theory, Earth
formed by…
the Nebular Hypothesis
…where our solar system evolved from a enormous
rotating cloud of dust made mostly of hydrogen
and helium about –
4.6 billion years ago
1
II.
Earth’s Shape and Size ( it’s roundish and big!)
A. How do we know Earth it’s round? …what is the
evidence?
1. Viewing Photographs of Earth from Space provide
us with a direct observations of Earth
This has only been possible since we entered the space
age (1960’s),
Remember observations are what we take in with our
senses- inferences (conclusions) are based on these.
Ex. Those clouds are black (observation), it seems like it’s going to rain (inference)
But humans knew the Earth was a round (a
sphere) before the 1960’s right? How?
2. Ships appeared to be sinking
But would “magically” rise up from the sea upon return
2
3. A lunar eclipse shows the curved shape of Earth
4. The changing position of the North Star (Polaris)
Early travels in the northern hemisphere noticed that the height
or angle of the North Star above the horizon changed when
traveling north-south…only possible on a sphere
Next up, the Big Ideas:
Why is it round in the first place?
Do we live on Earth or inside Earth?
Why does it look smooth when viewed from space since we have
gigantic mountains and deep valleys?
3
B. Why objects in space (i.e. planets, comets, etc.) tend
to be round….
Equal Dimensional Gravity
A brief refresher on Gravity The force of attraction between objects
You know it as the force that
keeps you on the SURFACE OF
EARTH and gives us our
orientation of up and down
Are Aussies upside down?
The bigger picture …. read
Because smaller objects (less massive) are attracted to larger
objects (more massive), objects in space (like the planets) tend
be round with the more massive elements collecting in the cores
during formation which then attracts other matter outward in 3-D
Hey! Whose upside down here?
4
C. But is Earth really Round?
Earth’s true shape is an OBLATE SPHEROID
How do we know this? It looks round from space.
1. Earth’s actual dimensions:
Polar circumference - 40,008 km
Equatorial circumference - 40,076 km
The roundness of the Earth then equals:
40,008 km
40,076 km
=
0.998
A perfect sphere = 1. Therefore, the Earth’s shape is slightly out
of round.
Why?
Earth’s rotation
A little global history tie in…
Eratosthenes, a Greek Astronomer who lived around 200 B.C. is
credited will being the first person to calculate the
circumference of a round Earth. His % error was ~ 15%
Hey, I thought Columbus first
Thought Earth was round in 1490’s????
5
A simple way to prove that Earth is not perfectly round.
2. Objects weigh more at the Poles than they do at the
Equator.
Because Earth is NOT perfectly round and because all objects
on Earth are “pulled” to the center of Earth by gravity:
Why? The distance from the
center of Earth to the surface is
less at the poles than at the
Equator.
C.
6
III. The Structure of the Earth
Based on density.
A. Atmosphere – The shell of gases that surrounds
the Earth.
Least Dense Sphere
B. Hydrosphere –The water on Earth: oceans,
lakes, rivers, and includes groundwater (water in
the ground)
C. Lithosphere (Geosphere) – The solid, outer shell
of the Earth composed of rock and soil.
Most Dense Sphere
All 3 layers can be further broken down.
Major understanding…
The thicknesses of these layers are a tiny fraction of the
overall size of Earth. This is why from space, the Earths’
surface looks smooth and landscape features such as
mountains are not visible from space.
So, how do we study very large (or very
small) objects?.... we make models of them.
7
IV. Models – Used to represent large natural objects
(sometimes small) or events so we can better understand
them.
Most often, they are scaled-down versions of the real thing.
True Scale
Some Examples: A globe, a map, a weather map
Exaggerated
Scale
They are often EXAGGERATED to show more detail
8
V. Locating Positions on Earth
A. Earth’s Coordinate System – A grid of imaginary
lines used to locate a particular position on the surface
of the Earth.
1. Latitude – The angular distance North or South of the
Equator
Lines of latitude are called Parallels because they form
circles around the Earth which are parallel to the
Equator.
Some Important Latitudes:
North Pole
Arctic Circle
Rochester
Tropic of Cancer
Equator
Tropic of Capricorn
Antarctic Circle
South Pole
90º N
66.5º N
43º N
23.5º N
0º
23.5º S
66.5º S
90º S
In the Northern Hemisphere, Latitude can be determined by two
methods:
1. The altitude of Polaris
VERY IMPORTANT
2. The angle to the Equator
1 degree of latitude on Earth equals about 112 km (70 miles)
9
This one is always on the
test…the guy on the right is using an
astrolabe to measure the star
Polaris…pay attention to what I do
up front.
Altitude of Polaris = _______________
Latitude = ______________
Using the last page, his is located on the …
This is what an astrolabe looks like
Two easy steps to find the North Star (Polaris)
1. Use the “pointer stars” in the
Big Dipper (Ursa Major)
2. The North Star is the last star
in the handle of the Little Dipper
(Ursa Minor)
Using Page 3 of ESRT’s , where would you expect to find Polaris
in Rochester?
10
2. Longitude – The angular distance East or West of the
Prime Meridian (0˚) – located in Greenwich, England.
Lines of longitude are also called Meridians and all pass through
both the North and South poles– they are not parallel!
What are:
What point is:
The coordinates of point A? _________
30˚N, 80˚W_________
The coordinates of point D? _________
60˚N, 50˚W_________
The coordinates of point C? _________
20˚N, 70˚W_________
Why can’t one distance be given for the distance between 1˚ of longitude?
It is common practice to always state latitude before longitude.
1˚can be broken down in 60’ (minutes), 1’ can be broken down into 60”
(seconds)
11
3. Longitude and Time
a. Time Zones –The Earth is divided into 24 time zones
15ºof longitude apart.
Why?
The Earth, a sphere, is 360˚ around and takes
approximately 24 hours to rotate (spin on its axis) once.
Therefore, the Earth rotates 15º per hour
(360º/24 hours = 15º/hour)
Which way does the Earth rotate?
b. The Prime Meridian (0˚)
a. West (W Long.) of the Prime Meridian – subtract
time
East (E Long) of the Prime Meridian – add time
b. Standard time on Earth is based on the Prime
Meridian – Called Greenwich Mean Time (GMT)
For every hour of difference in time between an
observer and Greenwich Mean Time (GMT), the
observer is 15º away from the Prime Meridian.
For practice:
Using 75º W, what time is it right now in Greenwich, England?
3. International Date Line – Located at 180º longitude
(E or W); West of the IDL a new day begins!
12
B. Maps - Show Earth’s surface on a plane (2-dimensions).
Good maps show shape, distances, and direction.
1. Map Projection - A method of representing the Earth as
a map.
Some examples include mercator, gnomonic, and polyconic.
2. Map Scales - The ratio of distance on the map to the
distance on Earth.
Three kinds of scale:
a. Verbal Scale – Ex. “1 inch = 50 kilometers"
b. Graphical Scale c. Numeric Scale - Written as a fraction. Ex.
1:1,000,000
3. Compass Directions
No one map can accurately represent all of Earth because
Earth is round. Therefore, all maps show some kind of
distortion! Globes on the other hand, more accurately show
the Earth’s surface.
13
C. Complex Maps - Maps that show a 3rd dimension in an
area (space).
The area of the map is defined by:
1. Field – Any region of space that contains a
measurable quantity at points within that space.
Ex. temperature, air pressure, elevation.
Fields value are dynamic and often change in time.
And are constructed by drawing:
2. Isolines – Lines connecting points of equal value or
quantity that exist within the field.
Ex. Isotherms, Isobars, contour lines.
The result is an:
3. Isoline Map (A Complex Map) - A map illustrating the
measured quantity as it fits in space.
Ex. Weather Maps, Topographic Maps
14
4. Topographic Maps – Models that show the shape of the
Earth’s surface (topography) by connecting points of equal
elevation with contour lines. They are also called contour
maps.
Features of topographic maps -
a. Mean Sea Level (MSL) – Serves as the basis for
elevation and is always equal to a zero (0) contour line.
b. Benchmarks – Points on a topographic map that
represent an exact elevation. They are identified by
“BM ___”
c. Contour Interval - The difference in value between two
contour lines on a topographic map. The contour
interval is constant throughout the map.
Index Contours – Contour lines that have the
elevation labeled.
d. Hachures – Used to represent depressions or
holes on a contour map. The first hachured
contour line has the same elevation as the
contour line next to it.
e. Rule of the “V”s – The bends in contour lines point UP
whenever they cross a river, stream, gully, ravine, etc.
15
f. Slope (also called Gradient) - Contour lines that are
close together indicate a steep slope; contour lines
that are spread apart indicate a gentle slope.
Gentle Slope
The Gradient can be measured by
determining the change in elevation over the
change in distance.
Found on Page 1 of the ESRT’s:
Steep Slope
g. Profiles – Constructed to show the 3rd dimension by
using the contour line value between two points.
16
III.
Vocabulary
1. Oblate Spheroid
2. Polaris (North Star)
3. Altitude
4. Latitude
5. Gravity
6. Centrifugal Force
7. Stratified (layered)
8. Zones
9. Troposphere
10. Stratosphere
11. Mesosphere
12. Thermosphere
13. Tropopause
14. Hydrosphere
15. Lithosphere
16. Coordinates
17. Axes
18. Parallels
19. Meridians
20. Prime Meridian
21. International Dateline
22. Greenwich Mean Time (GMT)
23. GPS (Global Positioning System)
24. Field
25. Models
26. Topographic Map
27. Isolines
28. Isobars
29. Isotherms
30. Gradient
31. Contour Lines (Topographic)
17