Читать книгу (101 things to know when you go) ON SAFARI IN AFRICA - Patrick Brakspear - Страница 19

Africa - today

The magnificent diversity of life that we see in Africa today is living testimony to the extraordinary success of evolution, and the culmination of a 100 million years of climatic and geological change that started with the breaking up of Gondwana, the ancient super-continent that split to scatter Africa, Australia, Antarctica, India and South America across the southern hemisphere. Unlike many of the other fragments, the African continent shifted only slightly, and slowly, resulting in an evolution of animal and plant communities unlike anywhere else on earth.

Mountains, rivers, lakes, deserts & forests

Africa’s mountains, rivers, forests and open grass plains are all intimately connected to each other. Winds, caused by the formation of pressure systems, and affected by the spin of the Earth on its axis, pick up moisture evaporating off the oceans and sweep inland from the sea, their flow altered only by the chains of mountains that lie in their path. Forced upwards in order to flow over the peaks, most of this moisture condenses and falls as rain, hail or snow. This rain sustains the forests and savannah and the wildlife that live there, with all of Africa’s rivers rising from the huge central plateau and mountainous regions of the interior, only to flow back to the sea.

Mountains

These mountains include the Ethiopian Highlands or ‘Roof of Africa’, the Hoggar, Tibesti and Air Mountains found in the midst of the Sahara desert, the Atlas Mountains of Morocco and Algeria, Mount Cameroon in West Africa and the Drakensburg range in South Africa. Alongside these peaks is to be found the Great Rift Valley, which includes Mount Kilimanjaro (the name Kilimanjaro is comes from Swahili word kilima, meaning mountain and njaro means whiteness), Mounts Kenya, Meru and Elgon, the Aberdares, the Virunga volcanoes (Africa’s most recently active) plus the nearby Ruwenzoris or ‘Mountains of the Moon’.

Rivers

Four giant rivers, the Nile (the world’s longest), Congo, Zambezi (the world's oldest) and Niger – and a host of smaller waterways – drain the continent, directing water out to the sea.

Lakes

In places, enormous inland lakes (including Lakes Victoria, Tanganyika, Malawi, Chad & Turkana), deltas and floodplains sustain prolific and colourful gatherings of wildlife. Lake Victoria is the second largest in the world in terms of surface area, whilst Lake Tanganyika, which flows into the Congo River, is the second deepest in the world at 147m (4820ft), and amongst the clearest waters anywhere on Earth. Then there is the Okavango – the world’s largest inland delta.

Deserts

The Sahara, which covers one fifth of the African continent, is the driest and largest desert in the world. The Namib is the most ancient – at 80 million years old. In addition, dry arid lands cover virtually the entire Horn of Africa (Somalia and Ethiopia) and most of the south-west, including the Kalahari and the Karoo.

Forests

With the equator spanning its mid-section, and bringing warmth, sunshine and rainfall to Central and West Africa, this region is rich in tropical rainforests. Despite covering a mere 7% of its total land surface Africa’s rainforests are the primary hotbed of evolution. It is here that the forces of evolution have had longer to work than anywhere else on the continent – since the age of the dinosaurs. These same forests regulate the continent’s climate; cool it down and help to stem the advance of the desert; lock water and nutrients into the land and act as a massive sink for carbon, bound up in the fabric of the forest.

The Great Rift Valley

Named by the British geologist and explorer John Walter Gregory, the Great Rift Valley is one of the most significant geographic and physical features in East Africa. In fact this vast geological feature, that runs north to south for some 5,000 km from northern Syria in southwest Asia to central Mozambique, leaving a vast scar across the African landscape, is the result of the rifting and separation of the African and Arabian tectonic plates that began some 35 million years ago. The ongoing separation of East Africa from the rest of Africa, in association with other geological faults, has impacted areas as far south as the Savuti channel and the Okavango Delta in Botswana.

For most of its length, the Rift Valley is bounded by inward-facing escarpments, some 60kms (35 miles) wide and up to 1,000m (1500ft) high. A number of National Parks can be found along this Rift Valley, creating a protected environment in which diverse flora and fauna thrive in spectacularly scenic surroundings.

The Great Rift Valley is actually divided into two forks, the eastern rift and the western rift. The latter is surrounded by some of the highest mountains and deepest lakes in Africa, and forms a series of shallow soda lakes in Kenya, which attract thousands of flamingos and pelicans. This area is volcanically and seismically active and has produced the volcanic Mount Kilimanjaro and Mount Kenya, as well as the deep lakes, Victoria and Tanganyika. Evidence of volcanic activity along the rift is seen by the presence of numerous boiling hot springs and more active eruptions like those experienced in recent years in the Virungas bordering Uganda and the Democratic Republic of Congo (DRC). So violent have some eruptions been in the past that mountains have literally ‘blown their tops off’. Many such volcanic eruptions are followed by a weakened magma chamber that then collapses in on itself (a collapsed volcano or caldera). A classic example is Ngorongoro, the sixth largest caldera in the world, which is thought to once have had a peak as high as 4500m (14,700 ft). Part of this great explosion resulted in the spraying of volcanic ash and debris over a vast area, including the southern Serengeti, where the resultant shallow soils impeded the establishment of trees but encouraged mostly grasses, today known as the Serengeti plains.

In other places along the Rift, new mountains are in the making, such as the smoldering crater of Ol Donyo Lengai in northern Tanzania, which last erupted in 2007, and continues to belch steam from fumaroles in its crater.

The Rift System has also been a great source of archaeological and anthropological discovery, particularly evident at Olduvai Gorge in the south eastern Serengeti (see earlier in this chapter Africa – looking back).

African Natural World Heritage Sites

There are currently 45 world heritage sites in Africa, designated under the World Heritage Convention's natural criteria. Four of these are on the islands of Madagascar (2 sites) and the Seychelles (2 sites), with the rest spread across the continent from the Cape to Cairo. They cover every bio-geographical region and are arranged here according to each site's main ecological characteristics - so your journey of exploration can take you across the golden sands of the Sahara desert......to the continent's highest peaks.....through the Great Rift Valley.....and into the strange worlds of the Cape Floral Region and Madagascar.

For a full listing of Africa's World Heritage Sites see Appendix A - Africa's World Heritage Sites. “Africa…it grabs hold of your heart, and never quite lets go.”- Robert Ruark, author.