Ophiolites on EARTH Magazine

Oman ophiolite suggests subduction started with a shove

Fri, 21 Dec 2018 10:28:47 -0500

Past research has suggested two mechanisms by which subduction zones may form along an area of lithospheric weakness: spontaneous sinking of denser crust and lithosphere, and forced convergence driven by lateral movement of a plate. A new study suggests that the latter was responsible for the formation of a fossil subduction zone off the Arabian Peninsula beginning about 104 million years ago. Credit: K. Cantner, AGI.

Plate tectonics is a fundamental control on how Earth operates and is important for the planet’s habitability, but how this crustal recycling process got started has long been a mystery. A new study examining some uniquely coupled metamorphic and volcanic rocks in Oman is adding some needed clarity about the initiation of subduction zones, a critical component in plate tectonics.

Travels in Geology: Northern Oman: Stunning canyons, towering dunes and the world's largest ophiolite

Mon, 09 Apr 2018 15:41:50 -0400

Wadi Nakl, the Grand Canyon of Arabia, is just one of Northern Oman's many highlights. Credit: Lon Abbott and Terri Cook.

Hot, off-the-beaten path and situated amid an oftentimes turbulent region, Oman may not top many travelers’ lists of desired destinations. But if you’re into geology, it should: The small sultanate, itself politically stable, hosts the world’s biggest and most intact ophiolite, along with stunning canyons that plunge into turquoise swimming holes, lush palm oases and Bronze Age tombs, pristine beaches where endangered sea turtles struggle back to the sea after laying their eggs, and endless fields of sand dunes where you can camp beneath the stars. You’ll come for the ophiolites, and stay for the rest.

Down to Earth With: Tectonicist Eldridge Moores

Wed, 13 Apr 2016 18:00:05 -0400

Eldridge Moores at the Cordelia Fault, a branch of the San Andreas Fault in the northern Coast Ranges, on a field trip for the general public in March 2010. Credit: Judy Moores.

“When Eldridge Moores was 10 years old, his family lived in Crown King, Ariz., a tiny, remote mining settlement high in the rugged Yavapai Mountains northwest of Phoenix. Money was tight and his family rarely traveled, so Moores vividly remembers a holiday road trip to visit his father’s relatives near San Francisco. The Bay Area left a deep impression on Moores, and, at the end of the journey, upon reaching the first of four switchbacks on the narrow dirt track that led up to Crown King, Moores vehemently pronounced that he would do everything he could to get out of there.

Benchmarks: August 1975: Geotimes magazine inspires name of rock formation: A Q&A with Tony Alabaster

Fri, 20 Nov 2015 10:58:02 -0500

The pillow lavas pictured here on the cover of the August 1975 issue of Geotimes magazine were later named the Geotimes unit after the magazine. Credit: AGI.

In August 1975, an intriguing rock formation in Oman appeared on the cover of Geotimes magazine, EARTH magazine’s predecessor. This pillow lava — a type of rock that forms when hot molten basalt flows into water, such as happens in Hawaii, or erupts underwater — is one of the lowermost units of the now-famous Semail ophiolite sequence. Ophiolites, pieces of ancient oceanic crust and upper mantle later uplifted and exposed on land, were a hot geological topic in the 1970s, because they helped illuminate the process of seafloor spreading, a key puzzle piece supporting the then-revolutionary theories of continental drift and plate tectonics.

Travels in Geology: Cyprus: Island of Oceanic Crust

Thu, 22 Oct 2015 11:22:53 -0400

The soul of Cyprus lies in the Troödos Mountains — a rare, intact sliver of ancient oceanic crust — and in the beautiful mountain villages dotting their slopes. Credit: ©Shutterstock.com/Konstantin Kopachinsky.

The eastern Mediterranean island of Cyprus played a pivotal role in the development of plate tectonic theory. Thus, when planning a recent eastern Mediterranean trip, we, as geologists, deemed it almost blasphemous not to include a visit to Cyprus on our itinerary. We had to see for ourselves the rocks that were so instrumental to the development of this geological paradigm. When our research revealed that Cyprus also hosts famous archaeological sites dating from Neolithic to Roman times, Byzantine churches listed as a World Heritage site, classic Mediterranean cuisine and wine, and gorgeous beaches, the decision to visit Cyprus was an easy one.

Skinned oceanic plates may be origin of ophiolites

Tue, 09 Dec 2014 11:48:33 -0500

Long recognized as slivers of oceanic crust incongruously emplaced on land, ophiolites are distinctive sequences of basalt, gabbro and peridotite found globally near former and current convergent zones, where oceanic tectonic plates subduct under continents. But scientists don’t have a clear idea why or how ophiolites split from downgoing plates and find their way onto land. Now, a new study suggests part of the answer may relate to weak layers of mantle that allow oceanic crust to be peeled, or “skinned,” from subducting slabs as they descend.