Earth’s Landmasses
Earth’s Landmasses
 There
are only four major landmasses on Earth.
 A continent is a landmass that measures millions of
square kilometers and rises a considerable distance
above sea level.
 Each continent has at least one large area of very
old rock exposed at its surface called the shield.
 Shields form the cores of the continents.
The Continents
 There
are seven continents:
 Asia
 Africa
 Australia
 North America
 South America
 Antarctica
Earth
 The
largest landmass on Earth consists of three
continents – Asia, Africa and Europe.
 The second largest landmass consists of the
continents of North America and South America.
 The third largest landmass is Antarctica. It is
about twice the size of the United States.
 The smallest landmass is Australia.
Antarctica
 Antarctica
is very different from the other
continents.
 It is almost completely covered by a thick icecap
which covers 34 million square kilometers. It
contains 90% of the ice on Earth.
 It is the coldest area on Earth. In 1983, Volstok
dropped to nearly –89.2 degrees C.
 Many scientific stations have been built here.
Australia
 Australia
is the smallest landmass still considered
a continent.
 It is the only continent that is a single country.
Changes in the Earth’s Surface
 Over
billions of years, the surface of the Earth has
changed many times.
 Several factors produce these changes;
 Weather conditions such as heat and wind change
the surface.
 Running water reshapes the land.
 Earthquakes and volcanoes cause major changes.
 People also alter the Earth’s appearance.
Topography
 Scientists
refer to the shape of the Earth’s surface
as its topography.
 The Earth’s topography is made up of different
kinds of landscapes.
 A landscape is the physical features of the Earth’s
surface found in an area.
Landscapes
 There
are three main types of landscape regions:
mountains, plains and plateaus.
 One characteristic of a landscape region is
elevation, or height above sea level.
 The difference is a region’s elevation is called its
relief. If a landscape has high relief, there are
large differences in the elevations of different areas
within the landscape region.
Mountains
 Mountains
make up one type of landscape region.
Mountains are natural landforms that reach high
elevations.
 Mountains have narrow summits, or tops, and
steeps slopes, or sides.
 A mountain must rise at least 600 meters above the
surrounding land.
Highest Mountains
 The
highest mountain in the world is Mount
Everest, ( 8 km) a part of the Himalayas.
 The Himalayas extend from Tibet to Pakistan.
 The highest mountain in the United States is
Mount McKinley (6 km) in Alaska.
Mountains Age
 All
mountains did not form at the same time.
 Some mountains are very old, some young.
Mountains are built very slowly. The Rocky
Mountains began to form about 65 millions years
ago. It took 10 million years for them to reach
their maximum height. Geologists consider the
Rockies to be “young”.
Mountain Formation
 Mountains
can be formed in several ways.
 Some mountains result from the folding and
breaking of the Earth’s surface.
 Other mountains are created when hot magma
(liquid rock) from the Earth’s interior breaks
through the Earth’s surface.
Streams and Rivers
 Streams
and rivers in mountain areas move very
quickly. The higher and steeper the mountain
slopes, the faster the water flows.
 Mountains rivers and streams carry rocks of all
sizes. Streams and rivers often carve valleys in
mountains. Valleys in older mountains are wider.
Individual Mountains
 Individual
mountains, which are not part of a
group, can be found in parts of the world. They
are usually the products of volcanic activity during
which magma broke through the Earth’s surface.
 Examples of volcanic mountains are Fujiyama in
Japan, Vesuvius in Italy and Kilimanjaro in
Tanzania.
Mountain Range
 Most
mountains are part of a group called a
mountain range. A mountain range is a parallel
series of mountains that have the same general
shape and structure.
 A group of mountains ranges in one area is called a
mountain system. The Great Smoky, Blue Ridge,
Cumberland, and Green mountain ranges are all in
the Appalachian mountain system.
Mountain Belts
 Most
mountain ranges and systems are part of an
even larger group of mountains called a mountain
belt.
 There are two major mountain belts in the world.
 The Circum-Pacific belt rings the Pacific Ocean.
 The Eurasian-Melanesian belt runs across northern
Africa, southern Europe and Asia.
 The two belts meet in Indonesia.
Plains
 Another
type of landscape region is made up of
plains.
 Plains are flat land areas that do not rise far above
sea level. Plains have very small differences in
elevation. They are areas of low relief. The
difference in elevation in a plains may be less than
100 meters.
 Most plains have broad rivers and streams.
Coastal Plains
 A coast
is a place where the land meets the ocean.
Low, flat areas along the coasts are called coastal
plains. The Atlantic and Gulf coastal plains are
examples. The coastal plains of the United States
were formed when soil and silt were deposited on
the edge of the continent. In the past, shallow
oceans covered these areas. The oceans
disappeared and sand and silt were left behind
creating fertile farming land.
Interior Plains
 Some
low, flat areas are also found inland on a
continent. These areas are called interior plains.
Interior plains are higher above sea level (450m)
than coastal plains. The Great Plains are large
interior plains. They were formed as mountains
and hills that were later worn down by wind,
streams and glaciers. Interior plains have good soil
since sediments have been deposited by rivers and
streams.
Plateaus
 A third
type of landscape region consists of
plateaus. Plateaus are broad, flat areas of land that
rise more than 600 meters above sea level. Some
plateaus reach elevations of more than 1500
meters. Plateaus are not considered mountains
because their surfaces are fairly flat. Like plains
they have low relief, but unlike plains they rise
much higher above sea level.
Location of Plateaus
 Most
plateaus are located inland but a few are near
oceans. The plateaus near oceans often end in a
cliff at the edge of a coastal plain or in a cliff at the
coast.Plateaus have the same landscape for
thousands of kilometers. Some plateaus have been
deeply cut be rivers and streams that form canyons.
The Colorado River cuts through the Colorado
Plateau to form the Grand Canyon in Arizona.
Most are dry and used for grazing or mining.
Mapping the Earth’s Surface
 A map
is a drawing of the Earth, or a part of the
Earth, on a flat surface.
 The most accurate representation of the entire
surface of the Earth is a globe, a spherical model.
 Both maps and globes are drawn to scale. A scale
compares distance on a map or globe to actual
distances on the Earth’s surface.
Meridians
 Each
meridian is half of an imaginary circle
around the Earth. Geographers have named the
meridian that runs through Greenwich, England,
the prime meridian.
 Because meridians run north and south, they
measure distance east and west. The measure of
distance east and west of the prime meridian is
called longitude.
Distance
 The
distance around any circle, including Earth, is
measured in degrees.
 All circles contain 360 degrees.Each meridian
marks 1 degree of longitude around the Earth.
 The prime meridian is labeled 0 degrees longitude.
 Meridians to the west are called west meridian and
to the east, east meridians. They go from 0 to 180.
Time Zones
 In
one day the Earth rotates 360 degrees or 15
degrees every hour. Thus, the Earth has been
divided into 24 zones of 15 degrees longitude
each. These zones are called time zones.The
Earth rotates on its axis from west to east so the
sun appears to rise in the east and travel west.
Time zones become an hour earlier in each
zone.
Time Zones
 There
are four time zones in the contiguous United
States. From east to west they are: the Eastern,
Central, Mountain, and Pacific time zones. Hawaii
and Alaska are further west than the Pacific time
zone.
International Date Line
 The
international date line is located along the
180th meridian. When you cross this line going
east, you subtract one day.
 When you cross this line going west, you add one
day.
Parallels
 There
are also lines from east to west across a map
or globe. These lines are called parallels. Parallels
cross meridians at right angles.
 The parallel located halfway between the North
and the South poles is the equator.
 Because parallels run east and west, they measure
distance north and south which is known as
latitude.
Equator
 The
equator is labeled 0 degrees latitude.
 Parallels to the north of the equator are north
latitudes.
 Parallels to the south of the equator are south
latitudes. The distance from the equator to either
the North or South pole is one quarter of the
distance around the Earth. North and south
parallels are labeled from 0 to 90.
Types of Maps
 Maps
show locations and distances on the Earth’s
surface.
 They also show many different local features.
 Some maps show soil types in an area.
 Some show currents in the ocean.
 Some show small, detailed areas of the Earth.
Drawback of Maps
 Maps
have one serious drawback. Because they
are flat, maps cannot represent a round surface
accurately.
 A map is a projection or representation of a threedimensional object on a flat surface. When the
round surface of the Earth is represented on a flat
surface, it is distorted.
Mercator Projections
 There
are many different ways to project the
Earth’s image onto a map. One type of map
projection is Mercator projection. They are used
for navigation. They show the correct shape of the
coastlines. The sizes of land and water areas
become distorted in latitudes far from the equator.
Equal-Area Projections
 Another
type of map projection is called an equalarea projection. Equal-area projections show area
correctly. The meridians and parallels are placed
on the map is such a way that every part of the
Earth is the same size on the map as it is on a globe
but the shapes of the areas are distorted on an
equal-area projection.
Topographic Maps
 A map
that shows the different shapes and sizes of
a land surface is called a topographic map. This
type of map may also show cities, roads, parks and
railroads.
 Topographic maps show the relief of the land.
Contours
 Most
topographic maps use contour lines to show
relief. A contour line is a line that passes through
all points on a map that have the same elevation.
 The difference in elevation from one contour line
to the next is called the contour interval. For
example, in a map with a contour interval of 5
meters, contour lines are drawn only at elevations
of 0 meters, 5 meters, 10 meters and 15 meters.
Symbols
 Topographic
maps use symbols to represent
features.
 Symbols for buildings and roads are usually black.
Symbols for bodies of water such as rivers, lakes
and streams are blue.Green represents woods and
swamps.Contour lines are brown or red.
 All symbols are placed in a legend which explains
what each symbol represent.
Rules of Topographic Maps
 A contour
line of one elevation never crosses a
line of another elevation.
 Closely spaced contour lines represent a steep
slope since the elevation changes greatly over a
short distance.
 Contour lines that cross a valley are V-shaped. If a
stream flows through, the V will point upstream.
 Contour lines form closed loops around hilltops or
depressions. Hachures are also used to indicate a
depression.