Qualla: Afar triple junction

Afar triple junction: Introduction

Thu, 23 Apr 2026 00:00:00 GMT

Photo credit Val Rime, CC BY-SA 4.0. Three spreading ridges converge in the Afar region, and none of them are finished. The Red Sea is widening to the north. The Gulf of Aden is widening to the east. The East African Rift is stretching to the south for more than six thousand kilometers, from the Afar Triangle all the way to Mozambique. Where the three meet is a rare geological structure called a ridge-ridge-ridge triple junction - three lines of active continental separation intersecting at one point, each one peeling a different piece of Africa away from the rest. Geologists have been arguing since the late 1960s about what will happen here next, and so far the landscape has mostly refused to settle the question.

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Image: Val Rime | CC BY-SA 4.0

Afar triple junction: What Triple Junctions Do

Thu, 23 Apr 2026 00:00:00 GMT

Photo credit Map: USGS Edits: Kipala, Public domain. In 1969, geologists Dan McKenzie and Jason Morgan published a classification of triple junctions based on how the three boundaries move relative to each other. A junction where all three arms are spreading ridges is called RRR - ridge-ridge-ridge - and Afar is the textbook exampl...

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Image: Map: USGS Edits: Kipala | Public domain

Afar triple junction: Doming and Rifting

Thu, 23 Apr 2026 00:00:00 GMT

Photo credit Nehaoua, CC BY-SA 4.0. Rifting begins with heat. A mantle plume, a column of hotter-than-average rock rising from deep within the Earth, impinges on the base of a continent's crust and makes it do two things: dome upward, and eventually split. Both happened in East Africa, starting in the Late Cretaceo...

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Image: Nehaoua | CC BY-SA 4.0

Afar triple junction: The Red Sea and the Gulf

Thu, 23 Apr 2026 00:00:00 GMT

Photo credit Razashah1, CC BY 3.0. The two northern arms of the junction are already submerged. The Red Sea rift runs along the length of the Red Sea, starting from the Dead Sea in the north and ending at the Afar triple junction in the south. Within it sit submerged volcanoes like Jabal al-Tair, and the seafloor ...

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Image: Razashah1 | CC BY 3.0

Afar triple junction: The East African Arm

Thu, 23 Apr 2026 00:00:00 GMT

Photo credit DavidMPyle, CC BY-SA 4.0. Only the southern arm - the East African Rift itself - remains mostly above sea level. It runs north-northeast to south-southwest, fed by elevated heat flow from the mantle beneath Kenya and Afar. It splits into two branches as it travels south: the eastern Gregory Rift through K...

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Image: DavidMPyle | CC BY-SA 4.0

Afar triple junction: Will It Become an Ocean?

Thu, 23 Apr 2026 00:00:00 GMT

Photo credit DavidMPyle, CC BY-SA 4.0. Geologists disagree about what comes next for the East African arm. Some have suggested the arm will eventually fail - become an aulacogen, the classic name for a failed rift that once opened but then stopped, leaving a scar in the continental crust without ever producing a mid-o...

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Image: DavidMPyle | CC BY-SA 4.0