Dave Taylor's African Safari: Abiotic Factors of the Serengeti-Mara Ecosystem - Geology: The Underlying Rocks

Abiotic Factors of the Serengeti-Mara Ecosystem
Geology: The Underlying Rocks
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The geology of the Serengeti-Mara Ecosystem is an important abiotic factor in determining the kinds of things that live here. The region’s closeness to the Rift Valley and its many volcanoes means that for the last several million years lava flows and ash have changed the landscape. In places, they have enriched the soil allowing forests to thrive, while in other areas conditions have been created that prevent trees from growing.

Walking the Land

To walk the land of this ecosystem is to walk across one of the youngest geological regions on Earth. Much of what lies directly below your feet is less than three million years old. This material was laid down by volcanic eruptions, the last of which occurred in 1983 (see Volcanoes). Look around a bit, however, and you will see rocks that appear different from the others. In the southern part of the ecosystem, they emerge out of the grassy plains like miniature mountains.

These rocks are known as kopjes (pronounced "copies" - singular "copy"). They are really the tops of ancient mountains that have been buried by lava flows and volcanic ash. Deep under the volcanic debris lie layers of granite rock that date back to the time when the continents first formed. These rocks originated billions of years ago when the Earth’s crust was first forming. Rocks of the same age can be found in other places around the world. Canada’s Canadian Shield is of similar age (2.5 billion years old) and composition. (Granite is lava that has been put under tremendous pressure for millions of years.)

A World Torn Apart

When lava first came to the surface of the Earth and cooled, billions of years ago, it formed a super continent. Forces beneath the Earth’s surface cracked and broke up this super continent into several sections called "plates".

These great granite plates were torn apart and have, for billions of years, drifted across the hot magma that lies below the Earth’s crust. At times, Africa was connected to other continents in the manner that Europe today joins Asia. At other times, it was a huge island, isolated as Australia is today. These periods of joining and separating helped determine the uniqueness of Africa’s wildlife (see also The Great Rift Valley: Volcanoes and Plate Tectonics).

For example, crocodiles have been here, in one form or another, since before the dinosaurs roamed the Earth. The many members of this family scattered across today’s continents, speak of a time when the continents were more closely aligned and the crocodile’s ancestors were able to make their way from one to another. When the continents drifted apart, the crocodile populations became isolated and evolved into the species we know today.

Moving In, Moving Out

During the early age of mammals (less than 65 million years ago), Africa was isolated for a time. Here many unique species evolved that would later move out of Africa to populate the many other parts of the world. Elephants are a good example. Early elephants evolved in Africa and later forms migrated when continents were again connected to Europe, Asia and eventually to North America.

Other animals moved into Africa once the continents rejoined. The camel came originally from the Americas. So, too, did the horse, now represented in Africa by zebras.

Plant species also developed and migrated. There are, for example, no native cacti in Africa. Those you do see came with the Europeans over the last few centuries. (The migrations of plants and animals continues today but now they are also helped or hindered by humans.)

It is only in the last half of the century that we have begun to understand the importance of continental drift to the way ecosystems, both past and present, came to be.

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