LATITUDEA GEOGRAPHIC “BIG IDEA”

WITH MANY CONSEQUENCES IN

AFRICA

Latitude is a big idea that helps us understandmany other geographic features in Africa,

including patterns of rainfall, natural vegetation,

animals, fires, floods, crops, early civilizations, trade,

languages, slavery, and diseases like malaria.

Africa is the second largest continent(three times as big as the U.S.)

Here is Texas, at the correct size and latitude.

Most of Africa iscloser to the equator

than any part ofthe United States.

Equator

The equator runs throughthe middle of Africa.

This means that Africais a good place to studythe effects of latitude,because any process

that depends on latitudewill occur twice in Africa,

once north and once southof the equator.

The equator runs throughthe middle of Africa.

The continent extendsalmost the same distance

north and southof the equator.

North

South

Equator

There is a belt of rainy weatherthat is always close to

the equator.The Equatorial Rainy Belt

is centered over the equatorin March.

The Equatorial Rainy Beltmoves a few degrees of latitude

north in June.

The Equatorial Rainy Beltmoves back to the equator

in September.

The Equatorial Rainy Beltmoves south of the equator

in December.

The Equatorial Rainy Belt has moved throughout the year.

Rain is highest in places where the sun is most directly

overhead.

Once again,the Equatorial Rainy Belt

is centered over the equatorin March.

For example, there is a belt of rainy weather

that forms where the sun is almost straight up in the sky.

This Equatorial Rainy Beltis always close to the equator,

but it moves a few degrees of latitude north and south in different seasons.

Click to see how.

This animation works if you can run a

Microsoft PowerPoint.

In March,the Rainy Belt isnear the equator.

The blue area gets more than 4 inches per month.

The blue area gets more than 4 inches per month.

In June,the Rainy Belt is

north of the equator.

The blue area gets more than 4 inches per month.

In September,the Rainy Belt is

back near the equator.

The blue area gets more than 4 inches per month.

In December,the Rainy Belt is

south of the equator.

The Zambezi Rivertends to make floodswhen the Rainy Belt

is south of the equator.

In summer, the famous Nile River of Egyptand the Niger of West Africa

are likely to flood.

When the Rainy Belt moves north, the famous Nile River of Egyptand the rivers of West Africa

(like the Niger) are likely to flood.

In your history books,you probably read thatfloods were importantfor the development

of ancient civilizations.

The important thingto remember is that

the number of rainy days per year

depends on latitude.

At low latitudes(near the equator),

it is hotand rainyin everymonth.

The important thingto remember is that

the number of rainy days per year

depends on latitude.

Near theTropic ofCancerand theTropic of

Capricorn,it hardly

ever rains.

Near theTropic ofCancerand theTropic of

Capricorn,it hardly

ever rains.

The important thingto remember is that

the number of rainy days per year

depends on latitude.

Near theTropic ofCancerand theTropic of

Capricorn,it hardly

ever rains.

And inbetween,

the numberof rainy

daysdependsmainly

on latitude.

Farther from the equator

meansfewer days

of rain.

A satellite imageclearly shows the effectof the different numbers

of rainy daysat different latitudes.

Rainforest

Grassland

Desert

The latitude bandsare also very obvious

on a map of ecoregions.

The main thingthat “messes up”

the east-westalignment of

natural regionsis the cooler

highland areasof east Africa.

Rainforest

Grassland

Desert

The influence of latitudeis especially obvious

when we examinethe places where fires

are likely to occurin different seasons.

In July, when theEquatorial Rainy Belt

is north of the equator,there are a lot of fires

in the shrublandssouth of the equator.

In January, when theEquatorial Rainy Belt

is south of the equator,fires are more common

north of the equator.

1. The desert areasnear the Tropic of Cancerdo not have enough plants to provide fuel for a wildfire.

2. The rainforest areasnear the Equator

have so much rain, the trees growing there

are too wet to burn.

If we show both fire mapsat the same time, we see

two basic principles:

The influence of latitudeis also obvious

when we look at wheredifferent kinds of animals

are likely to be found.

Chimpanzees, gorillas, and many kinds of birds

live in the tall treesnear the equator.

Camels are by farthe largest animals you might see in the desert

near the Tropic of Cancer.

Grasslands and savannasare the home of manyfamous large animals,

including giraffes, zebras, antelope, elephants,lions, and cheetahs.

Put all the animalson the map of rainy days,

and you can see how different animals liveat specific latitudes.

The highlands of east Africa

are coolerand drier than

the lowlandrainforest.

The main food cropsalso tend to grow

at specific latitudes(where each crop gets

the amount of rain it needs).

In the past, peoplelived in the latitudes where

they could hunt,grow food, or raise cattle.

This line of starsshows the capitalsof ancient empires.

The ancient empiresall had their centers

in the grasslandsnear fields of millet.

That is just dry enoughto avoid the diseases

(like malaria)that are commonin rainier places.

Malaria is transmittedby mosquitoes that live

in the latitudes that havelong rainy seasons.

(It makes sense, no?)

The floods of the Nilemade the soil better,but they also allowedmalaria mosquitoesto live in a desert.

The ancient citieswere the centers

of trading networksthat reached all the way

to India and China.

to India 1000 miles

Not surprisingly,they used camel caravansto carry the trade goods.

One very interestinginfluence of latitude

is on human languages.

In rainy environments,people could find almosteverything they needed

close to home.

When people don’t travel,the languages of each

community is likelyto become different.

Dryland people were luckyto have horses and camels,because they had to travel,often very long distances,

in order to find food and to trade for things

they couldn’t get at home.

To do their trading,they needed to haveat least one language

that they could useover a large area.

The language mapis especially important when we “fast forward”

to look at the slave tradeand colonial claims.

Seven differentEuropean countries

claimed coloniesin different parts

of Africa.

It is plausiblethat it was easierto capture slavesin areas where

people livedin small groups

and spoke many different

languages.

When European countriesdivided Africa into colonies,

they did not pay much attentionto the natural dividing lines

between environmentsor language regions.

Why might thatbe a problem?

The natural bordersbetween environmentsand language regionsrun mainly east-west(following lines of latitude),

but the colonial bordersoften go north-south,

especially in West Africa.

Think about what that meansfor countries like Nigeria,Ghana, Benin, or Mali.

This presentation showed one way to use the clickable mini-Atlas - to help us investigate some consequences of the big idea of latitude,

with examples from Africa.Latitude affects:

Climate – because the number of rainy days goes down as you go from the equator to the Tropic linesPlants and animals – because different plants require different amounts of rain, and different animals eat different kinds of plants.Floods and fires – which occur at specific latitudes in different times of the yearEconomy – because people grow different crops and hunt/herd different animals at different latitudesDisease – because diseases like malaria and yellow fever occur in hot, rainy places close to the equatorLanguages, empires, colonization, slave trading, and many other aspects of African history also have latitudinal patterns.

Copyright 2016, Phil Gersmehl

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