The Pillow Lavas of Oman Ophiolite

You don’t have to be a geologist to appreciate these marvelous rock formation known as Pillow Lavas found in the Hajar Mountains of Oman. Pillow lavas form when hot lava flows into water and cools rapidly forming a skin over the still molten rock. Underneath the skin, lava continues to flow forming a lobe, until the pressure of the magma becomes sufficient to rupture the skin and start the formation of a new lobe. This process produces a series of interconnecting pillow-shaped mounds of rock that look like toothpaste squeezed from a tube. Pillow lavas are found not only in the ocean but also under glaciers that overlie volcanoes. The presence of pillow lavas indicate that the area was once under water.

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Photo credit: www.travelinggeologist.com

In the Hajar Mountains of Oman, pillow lavas occur in what geologists call the Semail Ophiolite — a large slab of the oceanic crust and the underlying upper mantle that was uplifted and exposed above the sea level. Covering an area of approximately 100,000 square km, it is the largest and best exposed of its kind in the world.

The pillow lavas are exposed in the cliffs along the south side of the valley. These formation became famous when they graced the cover of Geotimes magazine back in 1975, and since then have been referred to as the “Geotimes” lava or “Geotimes” pillow lavas. Locally, they are known as Wadi Jizzi.

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