Introducing Physical Geography

1
Introducing Physical Geography

• Science!
• Spheres, Systems and Cycles
• Physical Geography, Environment, and Global
  Change
• The basics of geographic literacy

2
What Is Science?

• Part of a Knowledge System-
• We observe the world and make knowledge claims
• In science this is done by hypothesis generation
  and testing
• Cumulative testing leads to strong evidence, and
  claims about the state of the world
• Critical thinking is an important part of the
  process

Figure 1.1, p. 7
3
Four steps in scientific practice (simplified)

• Generate a hypothesis based on an observation
• Test the hypothesis by trying to prove it wrong.
• Record the results
• Report your findings
• - After the process is repeated many times,
  theory can be built and scientific knowledge is
  established

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Why is this important?

• Literacy in the scientific process is important
  to evaluation of claims.
• Much of this course is based on established
  knowledge.
• A challenge throughout the course, think
  critically about the information in the text and
  the lectures
• On to the science

5
Spheres, Systems and Cycles

• The natural systems and processes involved in
  physical geography are considered to operate
  within four great spheres (or realms) the
  atmosphere, the lithosphere, the hydrosphere, and
  the biosphere

Figure 1.6, p. 15
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Spheres, Systems and Cycles

• The life layer is the shallow Earth surface layer
  where the four realms (or spheres) interact and
  where most life forms are found

Figure 1.7, p. 15
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Spheres, Systems and Cycles

• Scale, pattern and process are three interrelated
  geographic themes
• Scale the level of structure or organization at
  which a phenomenon is studied
• Pattern variation in phenomenon observed at a
  particular scale
• Process how the factors that affect a phenomenon
  act to produce a pattern at a particular scale

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Spheres, Systems and Cycles

• processes operating in the four spheres are
  studied at different spatial scales or levels of
  detail (global, continental, regional, local,
  individual)

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Spheres, Systems and Cycles

• a system is a collection of physical processes
  that are linked and act together in an organized
  way
• a systems approach to physical geography looks
  for linkages and interactions between processes

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Spheres, Systems and Cycles

• Time cycles are periodic changes in system flow
  rates that occur over periods ranging from hours
  to millions of years

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Physical Geography, Environment, and Global
Change

• Physical geography is also concerned with the
  relationships between humans and their
  environments
• Environmental change is caused by both natural
  processes and human interference and this course
  addresses both
• How do we spatially contextualize these processes?

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The Earth as a Rotating Planet

• The Shape of the Earth
• Earth Rotation
• The Geographic Grid
• Map Projections
• Global Time
• The Earths Revolution around the Sun

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The Shape of the Earth

• the Earths shape is very close to spherical
  (oblate ellipsoid (flattened at the poles)

Earth
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The Geographic Grid

• Earths coordinate system is divided into 360
  degrees
• Each degree is divided into 60 minutes
• Each minute is divided into 60 seconds
• Port Columbus
• 39 deg. 59 min. 52.7 sec. N, 082 deg. 53 min.
  30.8 sec. W
• This division provides a grid of imaginary
  lines
• parallels (east - west)- Lattitude
• meridians (north - south)- Longitude
• Geographic Jumping Jacks

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The Geographic Grid
b) Longitude (meridians) 1 degree of longitude
111 km at the equator and 0 at the poles
a) Latitude (Parallels) 1 degree latitude
constant 111 km
Figure 1.3, p. 28
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The Geographic Grid
Latitude is the angle between a point on a
parallel and the centre of the Earth and a point
on the equator Longitude is the angle between a
point on a meridian and the centre of the Earth
and a point on the Prime Meridian
Figure 1.5, p. 29
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Map Projections
To make a map you need a Map Projection 3
properties to consider scale, area and
shape Think of a light at the centre of a sphere
which casts shadows on a surrounding
surface surface may be a cylinder, cone or a
flat plane
Cylindrical projection
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Map Projections

• Mercator Projection
• rectangular grid of meridians (straight vertical
  lines) and parallels (straight horizontal lines)
• meridians are evenly spaced, spacing of parallels
  increases with latitude
• straight line on map represents true compass
  direction (bearing)

Figure 1.9, p.31
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Map Projections

• Polar Projection
• centered on north or south pole
• meridians are radiating straight lines
• parallels are concentric circles
• spacing of parallels (scale fraction) increases
  outward from the pole

Figure 1.8, p.31
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Map Projections

• Goode Projection
• two sets of mathematical curves used to define
  its meridians
• indicates the true sizes of the Earths surface
  but distorts the shapes of areas

Figure 1.10, p.32
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Modern Cartography and GIS
GIS Geographic Information System a
computer-based system that allows maps, diagrams,
satellite images and aerial photographs to be
stored and manipulated uses geographically
referenced data spatially-referenced data can
therefore be used to solve complex planning
problems.
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Geographic Information Systems (GIS)
GIS data layers for each map layer, the
geographic location of a point on the Earths
surface must coincide
p. 35
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Geographic Information Systems (GIS)

• GIS allows you to store a lot of information with
  your map and build more complex scientific models
  across space

p. 13
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Earth Rotation
The earths axis is tilted 66.5 to the plane
of the ecliptic or from the perpendicular to the
plane of the ecliptic by 23½
Figure 1.16, p. 40
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Earth Rotation
The direction of the Earths rotation is
counterclockwise when viewed from above the north
pole or west to east when viewed with the north
pole up
Figure 1.2, p. 26
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The Earth's rotation has three important
environmental effects

• It imposes a daily, or diurnal, cycle of
  daylight, air temperature, air humidity, and air
  motion.
• It produces the Coriolis effect which deflects
  the flow of fluids (air and water) to the right
  or left of their original path in the northern or
  southern hemispheres, respectively.
• As the Earth rotates, the combined effects of
  both the moons and suns gravitational pull on
  different sides of the Earth creates a rise and
  fall of ocean water known as tides

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Global Time
based on the east-west position of the Sun a
solar day defined by one sun circuit solar noon
(at a particular location) is the time of the
highest solar angle the time is calculated by
the position of the Sun at selected meridians
(Standard Time)
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Global Time
the Earth rotates 15 per hour so time zones
differ by 1 hour (360/15 24 hours)
Figure 1.12, p. 36
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Global Time
Different days are observed on either side of the
International dateline (180th meridian 15 X 12
hours), 12 hours difference from the
Prime Meridian
Figure 1.13, p. 37
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The Earths Revolution around the Sun

• Revolution
• one complete circling around the Sun
• from above north pole in counterclockwise
  direction
• the path is not circular but is elliptical
• orbits on the plane of the ecliptic

E
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The Earths Revolution around the Sun
the Earth and Moon both rotate and revolve in a
counterclockwise direction (when viewed from a
point over the Earths north pole)
Figure 1.14, p. 38
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The Earths Revolution around the Sun
sun is not in the middle of the plane of the
ecliptic
Aphelion - the Earth furthest away from Sun
(July 4)
Perihelion - the Earth closest to Sun (January
3)
152 million km
147 million km
variation in distance of 3
33
The Earths Revolution around the Sun
the Earth rotates about its axis from west to
east once every 23 hours and 56 minutes the
Earths axis points same way (parallelism) as it
revolves around the sun
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The Earths Revolution around the Sun
at equinox, the circle of illumination passes
through both poles the subsolar point is the
equator each location on Earth experiences 12
hours of sunlight and 12 hours of darkness
Figure 1.18, p. 41
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The Earths Revolution around the Sun
Solstice (sun stands still) On June 22, the
subsolar point is 23½N (Tropic of Cancer) On
Dec. 22, the subsolar point is 23½S (Tropic of
Capricorn)
Figure 1.19, p. 41
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The Earths Revolution around the Sun
the latitude of the subsolar point marks
the suns declination which changes throughout
the year
Figure 1.20, p. 42
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The Earths Revolution around the Sun
the four seasons occur because the Earth
maintains a constant orientation (tilted 23½
with respect to the perpendicular to the plane of
the ecliptic) as it revolves around the sun
Figure 1.17, p. 40
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