Mike Searle

Tectonic Evolution of the Oman Mountains

You look out across the dry landscape, taking in the golden horizon. The land swirls back and forth, more reminiscent of its molten past than its solidified nature. But what you're seeing isn't the result of a sudden volcanic eruption. It's far greater than that. You are standing in Oman, on the site of decades of geologic discoveries, witnessing the very first effects of continental collision.

Dr. Mike Searle is a senior research fellow and professor of Earth sciences at the University of Oxford. He is also a field geologist whose passion lies in studying continental collision: how the tallest mountains formed, how the ocean floor made its way to the peaks, and how the earth folds upon itself. He has done extensive work in Oman for the last half century, mapping the geological structures there. He addressed the department on September 25th, showcasing his work and the wonders he has helped discover in Oman. In his words, "You can't fail to like Oman. It's a fantastic mountain belt, a wonderful country with friendly people, and the geology is spectacular."

So, what makes Oman so special? Oman is home to the largest ophiolite obduction in the world, meaning that a part of the oceanic lithosphere has been exposed after being thrust onto a slab of continental crust. Usually, oceanic crust undergoes subduction and travels back into the mantle while the continental crust stays on top. This anomaly creates a unique opportunity to study both the exposed mantle and crust, as well as the normally hidden boundary that separates the two. The Moho, which normally defines the line between the mantle and crust many kilometers below the surface, is so visibly distinct in Oman that it can be seen from space, and yet is often thin enough that in some places it can be covered with just a finger.

The location of the Oman formation is in and of itself uncommon. Searle conducted research in the 1980s that proposed that the ophiolite was formed above a subduction zone. They posited this after discovering "pillow lavas," large plumes of basalt formed as subduction forces magma upwards. Earlier studies of the ophiolite were not aware of this geological evidence because they were based in the southern portion of the country, where the pillow lavas were mostly eroded away.

Additionally, Searle stated, Oman boasts a number of other exceptional geological curiosities, such as the biggest anticline in the world. The large upward-arching fold is well preserved because Oman and Iran are just beginning to collide. This early-stage obduction is a unique feature of Oman's geology and is incredibly useful for studying the early effects of tectonic collision. Beneath the anticline lies a reserve of over half of the world's accessible oil, making the work in Oman vital to the world's energy industry. As continental collision meets the already complex ophiolite sheets, it causes beautiful swirls of rock in the desert landscape. In Searle's words, "everything goes completely crazy" as sheaths are thrust on top of each other and fold over themselves.

The distinct ophiolite exposure brings to question whether large-scale CO₂ sequestration could be possible in Oman. According to Searle, the serpentine within the ophiolite "has the potential to consume billions of tons of atmospheric CO₂ by converting it to solid carbonate." This reaction is possible only in exposed ophiolites. As geologists continue to study the remarkable structure, they may learn the key to help reverse our carbon footprint and solve the global warming crisis.

Mike Searle encouraged students to visit Oman, whether on their own or as part of the upcoming Hamblin Global Fieldtrip. It is a remarkable country of intense beauty and well worth visiting to see its unique geological story.

Stay tuned for the Hamblin Global Field Trip where the BYU geology department itself will explore the distant land of Oman!