East Africa‘s Great Rift Valley

Overview / Main Points

Geologists know a great deal about the tectonic plates that form the Earth’s crust around the world. They know in which direction plates are moving, how much pressure is being exerted on various plates, and why the movement of plates causes earthquakes. But according to an article in Geology.com, geologists are “still debating exactly how rifting” occurs on the earth’s crust, and the substance of the article (“East Africa’s Great Rift Valley: A Complex Rift System”) is a thorough scientific examination of old plates in East Africa that are splitting apart to create new ones — a classic case of rifting. This article explains what is known about this African rifting process, and it also explains that not everything is fully understood by geologists.

The process of rifting in this particular geological area of Africa — East African Rift System (EARS) — is the centerpiece of this article. In fact the new plate that is being created in the is tentatively being called the “Nubian Plate” (Wood, et al., 2012). A smaller plate that is moving away from the Nubian Plate (due to rifting) is being called the Somalian Plate. To the north of those two rifting plates is the Arabian plate.

Strengths of the article: Any reader would want to know why the rifting is taking place. The authors do their best to use plain non-esoteric language to explain what is happening in that particular area of Africa. In the fourth paragraph the authors speculate that the reason rifting is taking place in the EARS region is because “elevated heat flow from the mantle” — they refer to “mantle plumes” under the asthenosphere, which is below the lithosphere, between 46.5 miles and 124 miles beneath the Earth’s surface — is causing “bulges” in the topography. In other words, the heat from the molten hot core of the earth is causing the rifting. They suggest that rift formations like this one are usually “preceded by huge volcanic eruptions,” which it seems is information that might have been used earlier in the article. Are volcanoes expected any time soon? There is no explanation for that possibility. But what they do say is that they scientists are able to observe things above ground in the EARS area that previously have only been available for study under water.

Article weaknesses: On page two the authors write, “What else can we say about the Ethiopian and Kenya Rifts? Quite a lot actually.” This is very sophomoric narrative for scientists to be putting forth. Using a cliche like that tends to lessen the value of the science. It takes the authors quite a long time to get to one of the most interesting points of the article. That is, the rifting is important in terms of understanding human evolution. It seems like that fact could have been placed at or near the front of the article. There are many “hominid fossil finds” in the rift, which means that the evolution of humans can be traced by scientists because the evolution of the rift itself is giving clues to human evolution.

The weakness here is because the authors waited until the last page to present something about humans that is far more interesting than just information about tectonic plates and how crumbling plates may be creating newer plates. There are no known factual errors, but it would have been more compelling to begin the article with how a rifting situation teaches science about human evolution. And they way they explain the link to evolution is clumsy. Because the rift was there centuries ago, they write on page 3, it “…may have made East Africa more sensitive to climate changes which lead to many alternation between wet and air periods” (Wood, p. 3). The “environmental pressure” may have been the “drive needed for our ancestors to become bipedal and more brainy as they attempted to adapt to these shifting climates,” Wood writes (3). This is not very clear or understandable, but in the conclusion they achieve a bit more clarity. Because the local climate was altered, they explain in the conclusion, that may have “…in turn caused our ancestors to develop the skills necessary to walk upright, develop culture and ponder how such a rift came to be” (Wood, 3). That still doesn’t explain how climate change due to the rifting could cause early man (or apes) to stand up straight, or to be smarter, but it is more interesting than some of the other material in the article.

Works Cited

Wood, James, and Guth, Alex. (2007). East Africa’s Great Rift Valley: A Complex Rift System

Geology.com. Retrieved July 14, 2012, from http://geology.com/articles/east-africa-rift.shtml.