Chapter 1
Introduction to Earth
Physical Geography
A Landscape Appreciation, 9/e
Animation Edition
Victoria O. Alapo, Instructor
Geog 1150 – Weather & Climate
Introduction to Earth
Geography as a Field of Learning
Geography is from two Greek words, “Geo” –
Earth, and “Graphien” – to write.
Elements/Branches of Geography –
Physical & Human or Cultural (see next slide).
This class is concerned with Physical
Geography.
Also, see pg 2 (Fig. 1-1a and b) for interesting
info about Earth.
Elements of Geography
Table 1-1 (pg 1)
Interrelationships
among elements
Introduction to Earth
Environmental Spheres (next slide)
The Solar System
Size and Shape of Earth
The Geographic Grid
Earth Movements
Annual March of the Seasons
Telling Time
Environmental Spheres
Lithosphere
Litho, Greek for
“stone”
Atmosphere
atmo, Greek for “air”
Hydrosphere
hydro, Greek for
“water”
Biosphere
bio, Greek for “life”
L
Interacting
spheres
A
B
H
Figure 1-2
The Solar System
Figure 1-6: “Elliptical” orbits – Pluto is NO longer one of the planets in our
solar system as of 2006 (see page 8).
 The Size and Shape of Earth
“3rd Rock from the Sun” (93 million miles)
Size
Diameter – approx. 8,000 miles (12,800 km) at
the equator
5th largest in diameter
Fig. 1-6 (cropped)
Size and Shape of Earth
Earth’s highest pt: 29,000 ft above
sea level.
Lowest point: 36,000 ft below sea
level
More bulgy at the equator: a
difference of 0.3%.
As a result, it’s not a ‘true/perfect’
sphere (circle), but an “Oblate
Spheroid”, slightly flat on top and
bottom.
Figure 1-8
Angle of Tilt
See “imaginary
rotation axis”.
Interesting fact
about Earth:
The Earth tilts
towards the east,
at an angle of
23.5 degrees.
This is called the
“inclination of the
rotation axis”.
The Geographic Grid
The Combination of Latitude and Longitude Lines
Summary (Geographic Grid)
Longitude (also called Meridians)
Measures distance east and west around the globe,
beginning at the Prime Meridian
Important longitude lines: Prime Meridian &
International Date Line
0-180 degrees East or West
Latitude (also called Parallels)
Location on the Earth’s surface between the
equator and the north or south pole
Important latitude line: Equator
0-90 degrees North or South
The Geographic Grid
The Equator (next slide) – the line thru the earth’s
middle
Latitude (run north and south of Equator)
Longitude – E/W of the Prime/Greenwich Meridian
They are used to establish location, for navigation and
for telling time.
The circle is 360 degrees around; therefore since there
are 24 MAJOR longitude lines, each line is 15 degrees,
same as ONE HOUR. So 360 degrees = 24 hours.
The Equator
More interesting
facts about Earth:
Earth ALWAYS
points to
‘Polaris’, the
North Star (see
pg 17 & 18)
Earth moves/
rotates from West
to East.
Great and Small Circles
A great circle is the largest
circle than can be drawn on
a sphere and they bisect
the Earth into 2 equal
halves e.g.
1. The Equator
2. The Prime Meridian
3. The Sun’s Circle of
Illumination (see “Blue
Beauty” NASA slides)
Small circles are any other
circles that can be drawn.
Latitude: Parallels
There are 7 important
parallels.
Measures from 0º to
90º N and S of the
equator.
Also, the “Tropics” or
tropical areas are
hotter, due to the
‘bulge’.
See pg 12 – Tropic of
Capricorn (Australia).
Longitude: Meridians
See Greenwich Photos
0 degrees Longitude passes
thru Greenwich, England.
And it’s then measured East
and West.
Measures from 0º to 180º E &
W of the Prime/Greenwich
Meridian. See pg 14.
Established in 1884 at the
International Meridian
Conference in Washington,
D.C.
Also used for determining
World Time (every 15 degrees
is an hr).
Regions on Earth
(Latitude bands)
Low latitude » 0º – 30º N and S (close to Equator)
Mid latitude » 30º – 60º N and S
High latitude » 60º – 90º N and S (close to poles)
Equatorial » within a few degrees of the equator
Tropical » within the tropics between 23.5º N and 23.5º S
Subtropical » 25º – 30º N and S
Polar » within a few degrees of the North and South Pole
Earth Movements
Rotation on Axis (Daily)
One complete rotation is 24 hrs
Rotation Direction (West to East), see next
slide
Rotation Speed, see table and pg 15-16
Revolution Around Sun (Annual)
365 days, 5hrs, 48 minutes and 46 seconds,
simplified to 365.25 or 365 ¼ days
Leap Year
Rotation Direction
West to East
Rotation Speed
Now Table 1-5
Note: Always
constant speed,
only DISTANCE at
each location varies!
Annual March of Seasons
Solstices – Summer & Winter; unequal daylight
(see next slides)
Equinoxes – 12 equal hours of daylight; start of
Spring and Fall (anywhere between the 20th and
the 23rd)
Also, see Table 1-7 (pg 22)
Solstices
Equinoxes
Changes in Daylight
Time Zones
Accurate calendars have been kept by great
civilizations for 1000s of years – the Egyptians, Mayas,
Aztecs, Chinese, Indians, etc. Pg 23 (Babylon – 2,000
B.C.)
A.M. & P.M. are Latin words (pg 23). “Meri” (highest) is
the root word for “Meritorious”.
3 units of natural time – the year, month and day.
Everything else is man-made (hour, minute, second,
etc)
Time Zones
Standard Time – starts at the Greenwich Meridian
(GMT) or ‘Zulu’. Now called UTC (Universal Time
Coordinated).
All areas to the east of the Prime Meridian are ‘ahead’
in time, and all areas to the west are ‘behind’ in time.
Some countries have one time zone, while others have
several. Russia has 9.
International Date Line (further slides)
World Time Zones
U.S./Canada Time Zones
International Date Line
Starts at 180 degrees;
this is also where a
NEW DAY (new DATE)
begins i.e. 12 Midnight.
It is the OPPOSITE of
the Prime Meridian
(zero degrees
longitude) in Greenwich
i.e. 12 Noon
There is a difference of
12 hours between the
Prime Meridian (zero
degrees) and the
International Date Line
(180 degrees longitude)