#ring fault

Mount Gorongosa

This 1800-meter summit is found at an interesting site geologically – the southern tip of the East African Rift Zone in Mozambique sits in Gorongosa National park. Lake Urema, a lake filled by water running off from Gorongosa Mountain to the west of the park, sits only 14 meters above sea level. This summit can be viewed, even in profile, from much of the park – even though the mountain itself doesn’t sit in the park borders.

Although the low elevation and volcanic features of the East African Rift formed in the last few million years as part of the continent pulled apart, the mountain is far more ancient. The rocks mostly syenites, a type of coarse-grained igneous rock formed when molten magma cooled beneath the Earth’s surface.

180 million years ago during the Jurassic, swarms of igneous rocks erupted across what was at that time the Gondwana Supercontinent. The sequence of fractures runs from what is today Africa across Australia and into what is today Antarctica. Molten rock that rises beneath continents often interacts chemically with the continental rocks, mixing together and producing a rock composition distinct from what was there beforehand. This oval-shaped mountain is a single intrusion, formed about 180 million years ago as part of this swarm of igneous rocks called the Karoo Large Igneous Province. Today, parts of this large igneous province are being once again split apart as the East African Rift imposes on the area.

-JBB

Image credit: http://bit.ly/2j7AkzK