BY STAFF REPORTER
The East African Rift (EAR) or East African Rift System (EARS) is an active continental rift zone in East Africa. It began developing around the onset of the Miocene, 22–25 million years ago. In the past, it was considered to be part of a larger Great Rift Valley that extended north to Asia Minor.
A narrow zone, the rift is a developing divergent tectonic plate boundary where the African Plate is in the process of splitting into two tectonic plates, called the Somali Plate and the Nubian Plate, at a rate of 6–7 mm (0.24–0.28 in) per year. The rift system consists of three microplates, the Victoria Microplate to the north, and the Rovuma and Lwandle microplates to the south. The Victoria Microplate is rotating counter-clockwise with respect to the African plate. Its rotation is caused by the configuration of mechanically weaker and stronger lithospheric regions in the EARS.
The System is one of the geologic wonders of the world, a place where the earth’s tectonic forces are presently trying to create new plates by splitting apart old ones. In simple terms, a rift can be thought of as a fracture in the earth’s surface that widens over time, or more technically, as an elongate basin bounded by opposed steeply dipping normal faults.
Geologists are still debating exactly how rifting comes about, but the process is so well displayed in East Africa (Ethiopia-Kenya-Uganda-Tanzania) that geologists have attached a name to the new plate-to-be; the Nubian Plate makes up most of Africa, while the smaller plate that is pulling away has been named the Somalian Plate. These two plates are moving away from each other and also away from the Arabian plate to the north.
The point where these three plates meet in the Afar region of Ethiopia forms what is called a triple-junction. However, all the rifting in East Africa is not confined to the Horn of Africa; there is a lot of rifting activity further south as well, extending into Kenya and Tanzania and Great Lakes region of Africa. The purpose of this paper is to discuss the general geology of these rifts are and highlight the geologic processes involved in their formation.
The oldest and best defined rift occurs in the Afar region of Ethiopia and this rift is usually referred to as the Ethiopian Rift. Further to the South a series of rifts occur which include a Western branch, the “Lake Albert Rift” or “Albertine Rift” which contains the East African Great Lakes, and an Eastern branch that roughly bisects Kenya north-to-south on a line slightly west of Nairobi.
The rift is mainly created by heavy volcanic eruptions. These violent forces of nature are often associated with death and total destruction. However, it may come as a surprise that volcanic activity can positively impact the environment and people living in the region.
Some of the benefits occur in the short term as well as over hundreds to thousands of years, according to Dr. Tracy Gregg, associate professor for the University at Buffalo’s geology department (Accuweather.com).
One of the shorter-term benefits could be observed with recent large eruptions including 1991’s Pinatubo eruption in the Philippines and 1982’s El Chichón eruption in Mexico, which both exploded ash and sulfur gas into the stratosphere, according to Gregg.
“The sulfur gas combines with water in the atmosphere, creating microscopic droplets that can stay in the atmosphere for years,” Gregg said. “The effect of those aerosol droplets is cooling the lowest level of the atmosphere, which is the level in which we live and breathe.”
Both eruptions cooled the atmosphere about over a half a degree Celsius, she said. “It doesn’t sound like a lot, but when we’re talking about anthropogenic global climate change, volcanoes have actually helped to keep the world about 2 to 3 degrees cooler than it otherwise maybe,” she added.
A long-term benefit of volcanic activity is seen in the Hawaiian Islands’ very existence. “We’re seeing this right now on the Big Island of Hawaii with Kilauea’s current eruption, as lava is pouring into the ocean and creating new land,” Gregg said. “All of the land in the Hawaiian Islands was created this way.” This land formation can take thousands of years, she added.
Over 4.5 billion years, the amount of water that has been produced by volcanoes has actually given us the water that we have on Earth, Concord University volcanologist Dr. Janine Krippner told AccuWeather.
“It comes out of steam,” Krippner said. “Over time, it’s just built up the water that we have on this planet. Water can actually come out of magma itself, as well.”
Volcanoes have also helped create a large portion of Earth’s atmosphere, she added.
Fertile soil is another advantage of volcanic activity. “In places like Japan, Indonesia, Philippines and Hawaii, volcanic material mixed in with the soil provides a lot of important nutrients,” Krippner said. “It gives us really fertile soils, which are great for farming and crops.”
Volcanoes also provide a good environment for the formation of new habitats for animals, plants and insects, she said.
Hot springs and geothermal energy are additional benefits. “People use geothermal energy in places like New Zealand and Iceland,” Krippner said.
Places on Earth with the highest underground temperatures are located in regions with active or geologically young volcanoes, according to the Union of Concerned Scientists.
The most active geothermal resources are normally found along major plate boundaries where volcanoes and earthquakes typically occur, like the Ring of Fire, according to the University of Colorado Boulder.
Sulfur, copper and gold are produced from volcanic activity, Krippner said. Diamonds are also brought up to the surface from the mantle from a rare kind of magma, called kimberlite.
“Volcanoes also provide a lot of building materials,” Krippner said. “Volcanic material can be made into blocks, and a lot of the materials are mined, especially in places like Indonesia, where it’s used for conglomerate building blocks.”
The volcanic material can be ground down to help make cement, she added.
THE ETHIOPIAN HERALD AUGUST 24/ 2021
