East Africa Could Separate From the Continent Earlier Than Anticipated by Scientists—and a New Ocean Might Populate the Void
A recent investigation indicates that the fissure in Kenya and Ethiopia has progressed to a pivotal phase in the separation process, with water expected to inundate it in a few million years
Kenya’s Great Rift Valley
Shankar S. from Dubai, United Arab Emirates, via Wikimedia Commons under CC BY 2.0
Approximately 250 million years ago, the Earth’s current continents were consolidated in a supercontinent named Pangea. However, according to the well-recognized scientific theory of plate tectonics, the planet’s shifting outer shell—the crust—ultimately fragmented it.
This theory posits that massive rock slabs known as tectonic plates float on top of a molten mantle layer. These plates can diverge at places called rifts, which permits magma to ascend and integrate into the crust, forming new geological features.
Recently, scientists discovered that a rift in eastern Africa, extending through Kenya and Ethiopia, appears to be more advanced in the division process than previously understood—and that an ocean is destined to fill the void. The findings, released on April 23 in the journal Nature Communications, indicate it is the only recognized active rift in a significant stage prior to ocean basin formation, possibly elucidating why the area has retained such extraordinary fossils.
“Essentially, we now possess a prime opportunity to witness a crucial rifting stage that [has] fundamentally influenced all rifted margins globally,” states co-author Folarin Kolawole, a geologist at Columbia University, in a statement.
Kolawole and his associates examined the Turkana Rift, a zone approximately 300 miles wide where two tectonic plates are separating at a rate of about one-fifth of an inch per year. This area is part of the broader East African Rift System, which typically measures about 35 miles wide and extends roughly 4,000 miles from Jordan to Mozambique.
Quick fact: When did the Earth’s crust begin to shift?
In a study published in March, researchers identified the earliest known evidence of plate tectonics. Rock samples from Western Australia suggest that the Earth’s crust was shifting as early as 3.48 billion years ago, nearly one billion years after the Earth formed.
The team analyzed the section by examining how acoustic waves reflected off underground layers while integrating this data with other imaging information from beneath the surface. They then constructed a map to illustrate the sediment structure and the depth of the upper crust in the Turkana Rift.
In the rift’s center, the crust measures roughly 8 miles in thickness—substantially thinner than the more-than-22-mile-thick crust located farther away, as discovered by the team. This disparity is indicative of “necking,” a stage preceding ocean formation during which the Earth’s crust is stretched akin to taffy, resulting in a slender middle.
Though not every rifting episode leads to the disintegration of landmasses, “the identification of necking in the [East African Rift System] signifies that eastern Africa is set for continental fragmentation,” the authors assert in their study. Necking likely commenced around four million years ago following extensive volcanic eruptions, according to the team’s hypothesis. Furthermore, they believe that geological activity generated fine-grained sediments that quickly preserved hominin fossils, including the Turkana Boy, a 1.6-million-year-old Homo erectus skeleton, which is the most complete archaic human specimen found to date.
“The conditions were appropriate to maintain a continuous fossil record,” asserts study co-author Christian Rowan, a geoscientist at Columbia University, in the statement.
In a few million years, the team speculates, magma will rise between the diverging tectonic plates and create a new ocean floor. Water will flood in from the Indian Ocean, forming a new ocean that separates what is presently the African continent.
Grasping necking, a vital phase in rifting, enables researchers to uncover ancient vegetation, landscapes, and climates. In this instance, the volcanic activity that initiated the process seems to have preserved a collection exceeding 1,200 identified hominin fossils from the last four million years.
“What our study accomplished is an examination of the rift itself, the configuration of the rift at this location, and the ongoing processes—and connecting that to the fossil record to comprehend how this globally recognized fossil record has been established,” Rowan informs ABC News’ Julia Jacobo.