Unit I: Earth Dimensions

1
Unit I Earth Dimensions

• Review Book pp.19-30

2
Objective 1

• Describe the actual shape of the Earth and
  explain 3 pieces of evidence for its actual shape.

3
Earths Shape

• The Earth appears to be the shape of a sphere
  (round in circumference) when observed from space
  or scaled down to a model such as a globe.

Taken from http//earthobservatory.nasa.gov/IOTD/v
iew.php?id8108 on 8/30/11.
4

• However, by actual measurement, the Earth is not
  a perfect sphere.
• Instead it has an oblate shape, having a larger
  circumference around the equator than through the
  poles.

Taken from http//scienceblogs.com/startswithabang
/2010/11/weekend_diversion_save_the_wor.php on
8/30/11.
5

• Equatorial circumference 40,076 km
• Equatorial diameter 12,756 km
• Polar circumference 40,008 km
• Polar diameter 12,714 km

Taken from ccrpc.org on 8/30/11.
6

• Therefore the Earth is slightly bulged at the
  equator and slightly flattened at the poles.
• Thus the true shape of the Earth is best called
  an oblate spheroid.

Taken from http//www.onr.navy.mil/focus/spacescie
nces/observingsky/precession2.htm on 8/30/11.
7
Evidence for the Shape of the Earth
Animation
Taken from http//astrobob.areavoices.com/2009/02/
17/spectacular-photo-inspires-a-northern-journey/
on 8/30/11.

• Observations of the North Star (Polaris)
• Polaris lies in space practically over the
  geographic north pole of the Earth.

8

• Altitude
• Angle above the horizon measured in degrees.
• Latitude
• Position north or south of equator in degrees.

Taken from http//oxford-materialstechniques.com/d
ata/illust/019920568X/019920568X.latitude.1.jpg
on 8/30/11.
Taken from http//www.nmm.ac.uk/upload/img/altaz-s
tar2.jpg on 8/30/11.
9

• If Earth is a perfect sphere, the altitude of
  Polaris should be equal to the latitude of the
  observer on Earth.
• These two measurements are not exactly the same
  so therefore, Polaris gives evidence that Earth
  is not a perfect sphere but instead it is
  slightly out of round or oblate.

Taken from http//bdaugherty.tripod.com/gcseAstron
omy/images/fifty.jpg on 8/30/11.
Kid on a Bike
10
Photographs of Earth from Space

• When photos of the Earth taken in space are
  precisely measured, they show the Earth to be
  larger at the equator and flatter at the
  geographic poles.
• However, when drawn to scale on a piece of paper,
  the Earth appears to be perfectly round.

Taken from http//earthobservatory.nasa.gov/IOTD/v
iew.php?id8108 on 8/30/11.
11
Gravimetric (Gravity) Measurements

• Gravity
• Force of attraction between any 2 objects
• Since Earth has a large mass, smaller objects
  with less mass are pulled towards the Earth.

Taken from http//www.bbc.co.uk/schools/ks2bitesiz
e/science/images/earth_gravity.gif on 8/30/11.
12

• Law of Gravitation
• Gravitational force is proportional to the
  inverse square of the distance between 2 centers
  of attracted objects.

Taken from http//www.physicsclassroom.com/class/c
ircles/u6l3c2.gif on 8/30/11.
13

• So therefore, gravity and weight of an object
  anywhere on the surface of the Earth should
  remain the same (if the Earth is a perfect
  sphere).

Taken from http//xamplified.com/wp-content/upload
s/2009/02/acceleration-due-to-gravity1.jpg on
8/30/11.
14

• Precise measurements show that gravity does on
  remain the same.
• Objects located at the poles weigh more than the
  same object located at the equator. This
  difference is more than can be expected due to
  the centrifugal effect.

Taken from http//www.mrsciguy.com/sciimages/weigh
t.jpg on 8/30/11.
15

• Centrifugal effect
• Produced by Earths rotation, pushes objects away
  from the center
• Examples
• Amusement park rides like Gravitron or Round Up
• Spinning bucket of water trick (here)

Taken from http//www.psw-leisure.co.uk/images/Fai
rground/Large/roundup-fairground-ride.gif on
8/30/11.
Taken from http//home.bway.net/rjnoonan/humans_in
_space/gravity.gif on 8/30/11.
Taken from http//startswithabang.com/?p1718 on
8/30/11.
16
Objective 2

• Name the 3 spheres of the Earth and describe
  their unique characteristics.
• Be able to use ESRT p.14 to describe the
  atmosphere.

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Spheres or Parts of the Earth
The atmosphere extends several hundred km above
the Earths surface into space and is the least
dense of the 3 spheres.

• Atmosphere
• Hydrosphere
• Lithosphere

Taken from need-media.smugmug.com on 8/30/11.
18
Earths AtmosphereAtmosphere is the Air

• The atmosphere is stratified (layered) into 4
  zones each possessing distinct characteristics.
  ESRT p.14.

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Troposphere

• Most dense layer of atmosphere
• Lowest section of the atmosphere found between
  the Earths surface and the tropopause
• It is characterized by decreasing temperature
  with increasing altitude.
• The only zone of the atmosphere to contain water
  vapor.

20
Stratosphere

• Region above the troposphere and below the
  mesosphere where temperature increases with
  altitude due to the presence of ozone.

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Mesosphere

• Found above the stratopause and below the
  mesopause.
• Characterized by temperatures that decrease with
  an increase in altitude.

22
Thermosphere

• Lease dense layer of atmosphere
• Outermost zone found between mesopause and outer
  space where temperature steadily increase with
  altitude.

• According to ESRT p.14, what happens to Atm.
  Pressure as you increase in altitude through each
  of the zones?
• Atmospheric pressure constantly decreases.

23
Note that the temperature pauses then reverses
direction when switching from one layer to the
next. Now you know why they call it the
Tropopause.
24
Earths HydrosphereHydro means water, think
hydrant or hydroelectric.
What is Earths nickname?
Taken fromhttp//www.waterdeva.com/blog/wp-content
/uploads/blue-planet.jpg on 8/30/11.

• Approximately 71 of the Earths surface is
  covered with a relatively thin layer of water.
  (More dense than atmosphere)
• Includes marine (salt water) and freshwater
  (inland lakes and rivers).

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Earths LithosphereLithosphere is Land

• Lithosphere
• Continuous, outer solid rock shell of the Earth
• The lithosphere is often under the hydrosphere
  (More dense) and accounts for the general
  features such as mountains, valleys and the ocean
  floor.

Taken from http//www.physicalgeography.net/fundam
entals/images/lithosphere.gif on 8/30/11.
26
Objective 3

• Describe a coordinate system and be able to use
  latitude and longitude (degrees minutes) to
  determine a position on Earth.

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Earth Positions

• Coordinate System
• Uses a grid of imaginary lines and two points
  called coordinates.
• A fixed point can be located on a graph by
  identifying the axes ( the intersecting point of
  two lines).

Taken from http//www.euclideanspace.com/threed/so
lidmodel/geospatial/ellipsoid/earth.gif on
8/30/11.
28
What is the most commonly used coordinate system
for identifying points on Earths surface?

• Latitude and Longitude

Axes used are called parallels meridians.
Coordinate system based on observations of the
Sun other stars.
29
Parallels of Latitude

• The equator, located halfway between the
  geographic poles, is a circle which divides the
  Earth into the Northern and Southern hemispheres.
• Lines called parallels are drawn.
  These parallels
  decrease in size from the
  equator (0o) to the
  North Pole (90oN) and the
  South Pole (90oS).

Taken from http//www.smallboatgps.com/class/index
_files/image002.gif on 8/30/11.
30
Meridians of Longitude

• Lines connecting the North Pole and South Pole
  are called meridian.
• The Prime Meridian runs through Greenwich,
  England and has a longitude of 0o. Longitude is
  measured using the meridians, east or west of the
  the Prime Meridian (0o) to a maximum of 180o (the
  International Dateline).

Taken from http//www.sailingissues.com/nav2n.png
on 8/30/11.
31
Latitude Longitude Measurements

• Latitude and Longitude are measured in degrees.
• Latitude is degrees north or south of the
  equator. Longitude is degrees east or west of
  the Prime Meridian.

Taken from math.nus.edu.sg on 8/30/11.
32

• Latitude is often determined by using the
  altitude of Polaris above the horizon in the
  Northern hemisphere. In the Southern hemisphere,
  other stars are used.

Taken from http//astrobob.areavoices.com/2009/02/
17/spectacular-photo-inspires-a-northern-journey/
on 8/30/11.
33

• Longitude is based on the Sun.
• The Earth rotates from west to east, 360o in a 24
  hour period of time.
• How many degrees is that every hour?

Taken from resonanceswavesandfields.blogspot.com
on 8/30/11.
34
Objective 4

• Be able to relate longitude positions and time
  differences.

35
Comparing local time to GMT or UT allows you to
find your longitude.

• Every hour difference from GMT indicates 15o
  difference in longitude from the Prime Meridian.
• Each hour earlier than GMT indicates 15o west of
  Prime Meridian.
• Each hour later than GMT indicates 15o east of
  Prime Meridian.

earlier
later
36
U.S. Time Zones
Taken from http//www.socialstudiesforkids.com/gra
phics/timeszones_us.gif on 8/30/11.
37
Taken from http//wiki.naturalfrequency.com/files/
wiki/solar/time-zones.gif on 8/30/11.

• Example
• A clock indicates it is 4 hours later than GMT.
  What is your longitude?

38

• Modern navigational techniques such as GPS
  (Global Positioning System) uses signals from
  both Earth and orbiting satellites to determine
  latitude and longitude.

Taken from http//www.colorado.edu/geography/gcraf
t/notes/gps/gif/figure05.gif on 8/30/11.
39
Objective 5

• Be able to read and use field (contour or
  topographic) maps.

Objective 6

• Know the following terms and be able to apply
  them to a map field, isolines, gradient,
  contour interval, hachure marks

40
Position Charactertistics

• Field
• Region of space that contains a measurable
  quantity at every point.
• Examples/Types of Fields

Sample Field Model

• Gravity
• Magnetic
• Atmospheric Pressure
• Relative Humidity
• Temperature
• Pollen Count
• Snow Cover or Depth

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• Isolines
• Connect points of the same value
• Isobars
• Lines connecting points with same atmospheric
  pressure
• Contour lines
• Lines connecting points with same elevation
• Isotherms
• Lines connecting points with same temperature

Taken from http//www.mrsciguy.com/sciimages/isoli
ne.gif on 8/30/11.
Taken from weather.com on 8/30/11.
Taken from topozone.com on 8/30/11.
Taken from http//www.nc-climate.ncsu.edu/secc_edu
/images/IsobarsIsotherms.gif on 8/30/11.
42

• Isolines represent field characteristics in
• 2 dimensions.
• Isosurfaces represent field characteristics in
• 3 dimensions.

Taken from https//www1.nga.mil/kids/geoint/photod
ict/PublishingImages/dict-contourlines.jpg on
8/30/11.
Taken from http//www.berneda.com/teechart_vcl_fea
tures/images/SeriesTypeIsoSurface.PNG on 8/30/11.
43
Taken from http//img.tgdaily.net/sites/default/fi
les/imagecache/story_slider/stock/450teaser/space/
galaxy_simulation.jpg on 8/30/11.
Taken from http//www.geoblox.com/images/jetty_ima
ge.jpg on 8/30/11.

• Isoline maps and isosurfaces are examples of
  models. What is a model?
• Simplified representation of objects, structures
  or systems.

44
Field Changes

• Static
• Unchanging
• Dynamic
• Constantly changing
• Of these two terms, which one describes almost
  all fields?
• dynamic

45
Objective 7

• Use the gradient formula to solve problems.

46

• Gradient
• Average slope within field, shows rate of change
  of field from one place to another
• Formula
• ESRT p.1

47
Gradient Example

• Solve using 3 step method (Formula, Substitution
  then answer with label).

48

• Calculate the pressure gradient along a straight
  line between point A and point B on the map.
  Solve using the 3 step method.

49

• When isolines are closer together the gradient is
  steep and when the isolines are further apart,
  the gradient is shallow (less).

50
Contour (Topographic) Map

• Uses isolines (contour lines) to connect points
  of same elevation, usually based on sea level
  measurements.

Taken from http//www.adirondacknorthway.com/maps/
mtmarcySm.jpg on 8/30/11.
51

• Generally every 5th line is an index contour
  line. These lines are printed darker and give
  the elevation value.

Taken from http//www.therockerbox.com/Contour_Lin
es_A3.jpg on 8/30/11.
52

• Contour interval
• Difference in elevation between two consecutive
  contour lines.

53

• Hachure marks indicate downward slope and are
  represented by the following symbol..
• -----

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What advantage is there to using a topographic
map rather than an ordinary road map?
Taken from http//pics.city-data.com/topo/tpc15669
.png on 8/30/11.

• Topos show terrain or land surface.

55
Objective 8

• Make a profile from a contour map.

56
What is a profile?

• Vertical cross-section of land surface between 2
  points on a map.
• a side-view of map

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Steps for making a profile.

1. Place straight edge of scrap paper between the 2
   points on the map.
2. Wherever contour line meets edge of paper, place
   a mark on scrap paper and record elevation of
   that point.
3. Take scrap paper with all the marks against
   horizontal axis of graph.
4. Above each mark on scrap paper, plot point on
   graph according to vertical axis.
5. Connect all points with smooth line. (Remember to
   curve all peaks and valleys!)