Transcript African landscapes and their formation

African landscapes
and their formation
Size of Africa
• The United
States, China,
Europe, India,
Argentina, New
Zealand fit
within Africa’s
shores with
room for a
number of
smaller
countries.
One country, Democratic Republic of
Congo (Zaire), is as large as half of the
continental United States
Government institutions are located in
cities, far from rural areas
70%-80% of the population lives in
rural areas where infrastructure
is not developed
Africa is truly tropical: More area
between Tropics of Cancer and
Capricorn than other areas
Two implications
• More crop and animal
diseases and pests
• Limitations on
agricultural
production
High agricultural
potential
• 12 month growing
season
• not restricted by low
temperatures
No single line
continental divide
• Continent is a flat
plateau
• Few dramatic areas
• Atlas mountains to
the North
• Ethiopian Masif and
East African Rift
Valley to the East
• Cape ranges in
extreme south
High plateau landscape as in
Zimbabwe, -- lone and level plain
stretches for miles.
Altitude: the major part is
> 300 meters (shaded area)
• Areas of more
than 1000 meters
are illustrated in
yellow.
• Penguin in
Antarctica
Africa also has the lowest proportion
of its land area lying at sea level
• Rapid decent to the ocean
• Called the Great Escarpment e.g., coast of
Sierra Leone, Namibia and Eritrea
• The Great Escarpment creates an enormous
obstacle for communications and
transportation
• Roads and railroads must ascend sharply
from the coast inland creating both costs and
engineering problems.
• North and West
Africa are known
as Low Africa
• South and East
Africa, are known
as High Africa.
High Africa includes the two major
outstanding areas of the continent
• The Ethiopian Massif, where elevations > 4000
meters
• The Rift Valley Systems of east Africa seen
here as a "gully" running from the Red Sea in
the North to Southern Africa.
Mount Kilimanjaro in Tanzania
• Is a dormant
volcano
• Africa's highest
point, exceeding
5880 meters above
sea level
• Snow-capped
Mt. Kilimanjaro located very
close to the equator
Allows examination of an
important feature of the African
landscapes-• The effect of altitude on climate, vegetation
and farming systems.
With every 100 meters of elevation
• Temperatures
decrease 0.6
degrees
Centigrade or
1.1 degree
Fahrenheit.
• This means that
from sea level to
the top of Mount
Kilimanjaro.
Great shifts in vegetation types
• Analogous to what could be observed in a trip
from the equator to the north or south pole.
• Vegetation types range from tropical savanna
in the foreground to tundra vegetation at the
top.
Satellite image of Mount
Kilimanjaro
• Concentric
vegetation
belts can be
easily detected
• Desert
landscapes
tropical forests
are no farther
than 100
kilometers
away from
huge glaciers
Major parts of East and South
Africa are > 1000 meters
• Africa is
less
tropical
given
its
location
astride
the
equator.
Plateau areas feature a very
pleasant climate and farming
systems
• Unlike those usually found in tropical lowlands.
• In the Ethiopian Massif, moderate
temperatures of 16 degrees Celsius (61° F)
prevail year round
• Wheat growing is not an uncommon
phenomena
• The Irish
potato, a crop
also associated
with
temperature
climates, was
successfully
introduced in
Malawi (part of
High Africa)
Geological
Timescale of
Africa
• Much of
Africa's rocks
are counted in
billions of
years and
come close to
the earth's
estimated age
of 4.5 billion
years.
The rocks are old, weathered,
and leached
• Lack many essential plant nutrients
• Soils may form a serious constraint to
farming
• The world's most productive soils are
younger soils ones near rivers.
Africa's political boundaries,
were drawn in colonial times
• Seldom follow physiographic features
• Largely ignore ethnic configurations
• Have serious implications for the
development of many regions
Africa's rivers and coastline
This line represents Africa's
continental divide.
• All rivers and
streams
originating
east of this
line deposit
their contents
in the Indian
Ocean.
• All rivers
west of this
line flow into
the Atlantic
Ocean.
Three of the world's ten longest
rivers are in Africa
• The Nile is the world's longest river,
surpassing both the Amazon and
the Mississippi.
• The Zaire (Congo) river ranks 8th
• The Niger ranks 10th.
In volume of total discharge
•
•
•
•
The Nile is third
The Niger second
The Congo (Zaire) is first.
The Congo (Zaire) discharges 16
times more water per year than
the Nile.
The majority of
Africa's rivers
outside the
equatorial zone
have great
seasonal
variety in
volume.
Africa's rivers reflect the affects
of distinct dry and wet seasons.
• The rivers are nearly
completely dry for much of
the year, as is this one
• They are flooded during
the rainy season.
The Niger river
• Africa's second largest river
• Discharges at least 25 times
more water during the rainy
season than during the dry
season, when water is most
needed.
The African
farmer
• Has developed generally
well adapted farming
systems to match these
seasonal fluctuations
• Grows millet and sorghum
that are adapted to the
alternating dry and wet
conditions.
Maize / corn
• Does not have these
properties, and is more
susceptible to wilting.
• Maize from the New World
was introduced on a large
scale even in the drier
areas of Africa, because it
may give higher yields.
Another feature
of Africa's rivers
is related to
Africa's plateau
character
and the presence
of the Great
Escarpment
Many rivers interrupted
by rapids and falls
• Such rivers provide
poor access to the
interior of the continent
because they are
unavailable at vital
locations.
• This is one of the
reasons for Africa's
relatively long isolation
in the past.
However, African rivers possess
great hydroelectric potential
Continental Shelf is narrow
• The ocean floor often drops to a great depth
near the coastline.
• Developing a commercial fishing industry has
been slow since it lacks shallow waters
favorable to fish breeding and growing.
Africa's huge size, its tropical
location, its plateau-like relief and
extreme age, and peculiar rivers
• Make Africa unique among the
continents.
• Africa's physical characteristics to
facilitate our discussion of Africa's
climate, vegetation, soils and
economic studies.
African Landscapes and Their
Formation
Mountains, valleys and
volcanos in Africa.
• Caused by
–Faulting
–Volcanism
–Folding
Warping resulted in
depressions or basins
• Lake Victoria, Africa's largest and the world's
third largest lake is a broad, shallow basin
• Other basins are the Djout, Chad and Sudan
basin, Congo (Zaire) basin, and Kalahari
Basin.
Faulting caused the spectacular
East African Rift Valley
• The world's most extensive rift valley system.
• Most spectacular of all of Africa's surface
features.
The African plateau stops
suddenly, drops, and the Rift
Valley is created.
• The Rift Valley floor and the plateau
possesses climatic and vegetative
characteristics quite unlike the plateau above.
• The floor is often much drier and the
vegetation much sparser.
The second process related to
Continental Drift is volcanism.
• Volcanic and seismatic activity is relatively
heavy in East Africa
• Many volcanoes are found in the area
Volcanic activity
• Africa's largest active volcano, Mount
Cameroon, 4,000 meters high
• It erupted four times this century.
• Soils derived from volcanic rock are among
the most productive soils, and are generally
associated with intensive farming.
Folding formed Africa's Cape
Ranges and Atlas Mountains.
• Rocks bend not break alongside a fault,
under the influence of colliding land masses,
resulting in typical mountain chains such as
the Atlas Mountains and Cape Ranges.