Chapter 1 Introduction to Earth

Physical GeographyA Landscape Appreciation, 9/e

Animation Edition

Victoria O. Alapo, InstructorGeog 1150 – Weather & Climate

Introduction to EarthGeography 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”

Atmosphereatmo, Greek for “air”

Hydrospherehydro, Greek for “water”

Biospherebio, Greek for “life”

  

Figure 1-2

L

A HBInteracting

spheres

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).

“3rd Rock from the Sun” (93 million miles)

Size Diameter – approx. 8,000 miles (12,800 km) at the equator

5th largest in diameter

The Size and Shape of Earth

Fig. 1-6 (cropped)

Size and Shape of Earth

Figure 1-8

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.

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”.

Angle of Tilt

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 MeridianImportant 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 poleImportant latitude line: Equator0-90 degrees North or South

The Geographic GridThe Equator (next slide) – the line thru the earth’s middleLatitude (run north and south of Equator)Longitude – E/W of the Prime/Greenwich MeridianThey 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 CirclesA 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: MeridiansSee 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 SHigh latitude » 60º – 90º N and S (close to poles)

Equatorial » within a few degrees of the equatorTropical » within the tropics between 23.5º N and 23.5º SSubtropical » 25º – 30º N and SPolar » within a few degrees of the North and South Pole

Earth MovementsRotation on Axis (Daily)

One complete rotation is 24 hrsRotation Direction (West to East), see next slideRotation 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 daysLeap 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 SeasonsSolstices – 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 ZonesStandard 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 LineStarts 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)