Plate tectonics and its relevance in Africa

The theory of plate tectonics was first proposed by Alfred Wegener in the early 20th century. Plates are large areas of crust that cover the earth. Their movements give rise to amazing landforms, and many of these landforms are in Africa!

WHAT IS PLATE TECTONICS?

The idea behind plate tectonics is that there are eight large plates and many smaller ones on the planet’s surface. The plates are like the skin of the planet and are constantly moving slowly – centimetres each year. At the boundaries between plates are plate margins. Destructive plate margins are where two plates are moving into each other; constructive plate margins are where two plates are moving away from each other.

WHAT IS PANGEA?

Earth did not always look like it does today. 330 million years ago, all land on Earth was one giant continent. Geologists call this supercontinent Pangaea/Pangea. The evidence for Pangaea is in the shape of continents. The east coast of South America fits like a puzzle piece into the west coast of Africa. Similarly, if you rotate North America, it fits next to Europe and Asia. Over time, the plates moved apart and formed the continents we see today.

HOW DID THE EAST AFRICAN RIFT FORM?

The East African Rift is a valley formed by the African and Arabian plates moving away from each other at a constructive plate margin. It passes through Ethiopia, Kenya, Uganda and Tanzania. As the plates move apart, the crust at the centre stretches and sinks below sea level. A wide valley forms. When this happens, water can flow into the valley. In fact, this is how the Red Sea formed!

HOW DID MOUNT KILIMANJARO FORM?

Mount Kilimanjaro is the highest mountain in Africa and is nearly 6000 m above sea level. It consists of 3 dormant volcanoes (Shira, Mawenzi and Kiba). A dormant volcano is one that has not erupted for more than 10,000 years. Mount Kilimanjaro is also on the East African Rift. About 0.75 million years ago, lava burst through the stretched crust between the African and Arabian plates and landed on the surface. This eruption formed the Shira Volcano. Later, the Mawenzi and Kiba volcanoes formed in a similar way.

Volcanoes, earthquakes and mountains are just some of the landforms formed by plate tectonics. Plate tectonics therefore helps us understand why our world looks the way it is.

ANDREW MOODY

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