Oceans and Continents

1. Map Projections2. Oceans & Seas

Map Projections• Globe – no distortion, but bulky and

difficult to transport• Curved surface (3D) 2D Flat Surface• Approaches to transfer the spherical

earth on a two dimensional surface • Some distortions will always occur

Section 1 – Maps

Cartographers (map makers) today can make very detailed and accurate maps of the earth using photographs from satellites and much improved data collected on earth.

• Maps give a two-dimensional representation to a three-dimensional object. Even flattening the carved surface of a sphere onto a 2-dimensional surface changes the way it looks.

Map Projections• Homolosine Map – distorts the

continents as little as possible• cuts are made through oceans• Antarctica is only continent distorted.• Northeast Asia & Greenland are distorted

Map Projections• Sinusoidal Interrupted Equal-Area

Map – An interrupted projection is a way of reducing the distortion. • The world is split into segments (gores),

suitable for applying onto the surface of a physical globe.

Map Projections• Cylindrical-Projection Map – Projecting a

spherical surface onto a cylinder• Longitudes equally spaced• Latitudes unequally spaced • Scale is true along equator • Shape and scale distortions increase near poles• Best for equatorial or low latitudes

Topographic Map

• Physical features and contours

• Contour line – connects elevations of equal height

• Contour interval – vertical distance between contour lines

3-D Monterey Bay

Bathymetric Map• “Depth-measuring” map

2-D Bathymetry

Measuring Depths• Soundings – earliest with rope, now

with SONAR• (Sound navigation ranging)

• Multibeam sonar

Side-scan SONAR

Side Scan Graphic

Side Scan Data

Nautical Chart

Ocean Basins• The world ocean is divided into 4 major

ocean basins.• Arctic, Atlantic, Indian & Pacific

Ocean Basins• No natural boundaries entirely separate

the four ocean basins• Are one large interconnecting system

constantly mixed by winds, tides, currents, waves and upwelling

• 1955, the United Nations established the boundaries for oceans and continents

• Cover 71% of Earth’s surface

Arctic Ocean

Arctic

Arctic Ocean• Includes waters north of

the North American and Eurasian continents

• The central part of the ocean is permanently covered in about ten feet of ice.

• It is bounded from the Pacific by the Bering Strait and from the Atlantic at about the 650 latitude (just north of Iceland).

Atlantic Ocean

Atlantic

Atlantic

Atlantic Ocean 2nd largest and youngest Connects the polar ocean

waters

Located between the continents of North and South America, Europe, Africa and Antarctica.

Covers about 20% of the Earth's surface

Busiest shipping ocean

Crude oil and natural gas

Atlantic Ocean• The S shape of the

Atlantic ocean results in two distinct basins with their own circulation systems.

• In the Northern Atlantic currents flow in a clockwise direction, while in the Southern Atlantic currents flow in a counterclockwise direction.

Indian Ocean

Indian

Indian Ocean• provides major sea

routes connecting the

Middle East, Africa, and

East Asia with Europe

and the Americas

Pacific Ocean

Pacific

Pacific

Pacific Ocean Largest

Covers approximately one-third of the earth’s surface

More surface area than all the continents combined!

The tallest mountain in the world is found in the Pacific

Ocean: Mauna Kea of the Hawaiian Islands.

The Mariana Trench in the western North Pacific is the deepest point in the world

(almost 7 miles)

Earthquakes and Tsunamis common

Other Terms• Bay – an indentation of a shoreline

larger than a cove but smaller than a gulf

Other Terms• Gulf – an arm of a sea or ocean partly

enclosed by land, larger than a bay

SeasThe term sea is a term of tradition

and is not used consistently.

Some seas are enclosed lakes. (Caspian Sea and Sea of Galilee)

Some seas are partially enclosed or isolated from other sections of ocean.(Mediterranean Sea and North Sea)

“The Seven Seas” and “the South Seas” are terms of ancient times or of literature and not places on maps and charts.

Seas as Enclosed Lakes

Partially Enclosed Seas

Continents• Continents are large landmasses• Six major continental land areas

• Africa, Antarctica, Australia, Eurasia, North America, and South America

• Islands are smaller landmasses surrounded by water

Continents

NorthAmerica

SouthAmerica

Africa

Antarctica

Eurasia

Australia

The 1955 United Nations agreement divided the landmasses according to political boundaries.

Africa – continent bordered to the north by the Mediterranean Sea, to the west by the Atlantic Ocean, to the east by the Red Sea and the Suez Canal, and to the east-southwest by the Indian Ocean

Antarctica – continent of the South Pole

Australia – smallest of the continents – It is located between the Indian and Pacific Oceans.

Eurasia – a single continuous landmass that includes Europe and Asia – Asia includes Saudi Arabia and on political maps also includes Japan, Taiwan, Indonesia and the Philippines. Europe is separated from Asia by political boundaries set from the Caspian Sea north along the Ural Mountains to the Kara Sea.

North America – includes Canada, U.S., Mexico and Central America down to Panama. Islands in the Arctic Ocean are included in North America on political maps.

South America – includes all the countries south of Panama

Ice• Covers up to 10% of the total surface area of

the earth.• About 4% of the landmasses are ice-covered.• Covers about 5% of the ocean surface.• During the winter the area covered by ice

increases; in summer it decreases

Section 3 Locating Points on a Globe

There are two types of reference lines used to make accurate maps and to locate points or positions on globe, map or chart of the earth.

They are:1. Parallels of latitude2. Meridians of longitude

The primary reference lines are:a. The equator (latitude)b. The prime meridian (longitude)

The Equator, Hemisphere, Axis, and Directions

The Equator is a reference line drawn around the earth halfway between the north and south poles.

The earth rotates daily around the axis.

The north and south poles are the points where the axis enters and exits.

The Northern Hemisphere is the half of the earth north of the equator.

What continents are in the Northern hemisphere?

The Southern Hemisphere is the half of the earth south of the equator.

What continents are in the Southern hemisphere?

*hemi = half

Parallels of latitude

Latitude is the distance measured in degrees from 00 to 900 north and south of the equator.

Parallels of latitude are imaginary reference lines that form complete circles around the earth parallel to the equator and each other.

Every point on a parallel is the same distance from the equator.

Degrees of latitude are measured from an imaginary point at the center of the earth.

Except for positions located right on the equator (00), degrees latitude are always labeled to tell whether they are north or south of the equator.

Examples: Honolulu, Hawaii is on the 210 North

Parallel.Sydney, Australia is located on the 340

South parallel.

Longitude

Distance east and west of the Prime Meridian is measured in degrees from 00 to 1800.

All meridians of longitude are given in degrees east or west of the Prime Meridian.

Meridians of longitude are imaginary lines forming half circles passing from the North Pole to the South Pole.

The Prime Meridian (00), by international agreement is drawn through Greenwich, England.

Examples: Washington, D.C. is on the 770

West Meridian.Rome, Italy is on the 120 East

Meridian.

The International Date LineThe International Date Line is an

imaginary line running mostly along the 1800 meridian.

Events immediately right or left of the date line are 24 hours apart.

The International Date Line was adjusted to allow certain land masses to remain together in the same day.

LocationLines of latitude and longitude form a global grid

system.

Any point on the globe can be located by specifying its latitude and longitude.

So that a point can be located more exactly, degrees are subdivided into minutes and minutes into seconds. (Minutes and seconds do not refer to time, but to parts of degrees of an angle.

10 = 60 minutes (60’)1 minute = 60 seconds (60”)

Distance measured by marine and air navigators is in Nautical Miles.

1 nautical mile = 1.85 km (1.15 miles)

(1 nautical mile – 1 minute of an arc measured along a meridian of longitude.)

1 knot – 1 nautical mile per hour