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 many
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
• Great Escarpment e.g., coast of Sierra
Leone, Namibia and Eritrea
• Great Escarpment creates enormous
obstacles for communications and
transportation
• Roads & railroads must ascend
sharply from coast inland
•
Create costs and engineering
problems
• North and
West Africa
are Low
Africa
• South and
East Africa,
are High Africa
High Africa includes two major
outstanding areas of the continent
• Ethiopian Massif elevations > 4000
meters
• Rift Valley Systems -- East Africa
• Seen here as a "gully" running from the Red
Sea in the North to Southern Africa.
Mount Kilimanjaro in Tanzania
• Dormant
volcano
• Africa's highest
point, exceeds
5880 meters
above sea level
• Snow-capped
Mt. Kilimanjaro located
close to the Equator
With every 100 meters of elevation
• Temperatures
decrease 0.6
degree
Centigrade
• or 1.1 degree
Fahrenheit
• From sea level to
top of Mount
Kilimanjaro.
Great shifts in vegetation types
• Similar to a trip from the equator
to North or South Pole.
• Vegetation types range from
tropical savanna 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
near the
equator
Plateau areas feature a pleasant
climate and farming systems
• Unlike those usually found in tropical lowlands
• In the Ethiopian Massif, moderate
temperatures of 16 degrees C (61° F)
prevail year round
• Wheat growing is not an uncommon
phenomena
• The Irish
potato better
in low
temperature
climates, was
successfully
introduced in
Malawi (part
of High Africa)
Geological
Timescale of
Africa
• Africa's
rocks are
billions of
years old
• Close to the
earth's
estimated
age of 4.5
billion years
The rocks are old,
weathered, and leached
• Lack essential plant nutrients
• Soils may form 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.
• Rivers &
streams
originating
east of this
line deposit
contents in the
Indian Ocean
• Rivers west of
this line flow
into the
Atlantic Ocean
Three of the world's ten longest
rivers are in Africa
• Nile -- world's longest river,
surpasses the Amazon
and Mississippi
• Zaire (Congo) river ranks
8th
• Niger ranks 10th
In volume of total discharge
•
•
•
•
Nile is third
Niger second
Congo (Zaire) is first.
Congo discharges 16
times more water per
year than the Nile
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
• Some rivers nearly completely
dry for much of the year
• But flood 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
• Developed farming
systems to match these
seasonal fluctuations
• Millet and sorghum are
adapted to the
alternating dry and wet
conditions
Maize / corn
• Does not have these
properties--more
susceptible to wilting.
• Maize (New World
crop)introduced on 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
Poor access to the
interior of the continent
-- unavailable at vital
locations.
• One reason for Africa's
relatively long isolation
However, African rivers possess
great hydroelectric potential
Continental Shelf is narrow
• Ocean floor drops to great depth
near the coastline
• Commercial fishing industry slow
-- lacks shallow waters favorable
to fish breeding and growth
Africa's huge size, tropical
location, plateau-like relief,
extreme age, and peculiar rivers
• Make Africa unique among the
continents
• Physical characteristics
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.