The tectonic forces pushing the Arabian peninsula (top) away from Africa (foreground) have created the landscape seen here. As rifting in this region has progressed over geologic time, the chasms it creates have filled with water from adjacent oceans. The Red Sea (left) and the Gulf of Aden (right) seen in this northeast-looking view have formed in this manner. Connecting these two bodies of water is a narrow waterway known as the Bab el-Mandeb (“Gate of Lamentation”).
The Bab el-Mandeb is actually divided by the island of Perim into two waterways, the larger of which is 16 kilometers wide and 322 meters deep. The importance of this waterway and nearby port cities grew with the opening of the Suez Canal in 1869, which linked the Mediterranean Sea to the Red Sea. Currently, an average of 60 ships pass through this strait each day. The strait is a classic example of a “chokepoint,” or a geostrategic point crucial for the continued flow of ships. The territorial waters of the strait belong to Yemen, Ethiopia, and Djibouti.
The tectonic activity in this region has produced one of the few spots on the Earth where new crust (the upper layer of the Earth) is being formed on land that has the composition of oceanic crust (called basalt). This basalt covers the triangle-shaped land mass in the foreground, known as the Afar Triangle. Prior to the onset of rifting, the corner of the Arabian penninsula used to “fit” into Africa (like pieces in a giant jigsaw puzzle) in the spot now occupied by the Afar Triangle. Geologists have learned much about oceanic volcanism from the rocks and structures in this unique setting.
December 1993, image STS-61-93-13.