1.3 Gravity sliding onto Atlantic-type continental margins.1.2 Compressional telescoping onto Atlantic-type continental margins.Most obductions appear to have initiated at back-arc basins above the subduction zones during the closing of an ocean or an orogeny. When two continental plates collide, obduction of the oceanic crust between them is often a part of the resulting orogeny. Obduction often occurs where a small tectonic plate is caught between two larger plates, with the crust (both island arc and oceanic) welding onto an adjacent continent as a new terrane. Obduction occurs where a fragment of continental crust is caught in a subduction zone with resulting overthrusting of oceanic mafic and ultramafic rocks from the mantle onto the continental crust. John McPhee describes ophiolite formation by obduction as "where ocean crust slides into a trench and goes under a continent, a part of the crust - i.e., an ophiolite - is shaved off the top and ends up on the lip of the continent."
This assemblage consists of deep-marine sedimentary rock ( chert, limestone, clastic sediments), volcanic rocks ( pillow lavas, volcanic glass, volcanic ash, sheeted dykes and gabbros) and peridotite (mantle rock). Obduction of oceanic lithosphere produces a characteristic set of rock types called an ophiolite. Obduction, which is less common, normally occurs in plate collisions at orogenic belts (where an oceanic plate that is subducting scrapes some of its material onto the continental plate, making an accretionary wedge) or back-arc basins (places where the edge of a continent is pulled away from the rest of the continent due to the stress of plate collision). When oceanic and continental plates converge, normally the denser oceanic crust sinks under the continental crust in the process of subduction. Obduction is a geological process whereby denser oceanic crust (and even upper mantle) are scraped off a descending ocean plate at a convergent plate boundary and thrust on top of an adjacent plate. That’s also a shame because Obduction’s art is one of its strongest features, and you lose a bit of that here.An example of obduction: while most of the oceanic crust subducts below the continental crust down into the mantle, part of the crust is obducted, pushed onto the continental crust, forming an accretionary prism. I have a GTX 980 Ti in this machine and still had some stuttering with the graphics defaulted to Medium. You’re going to need one hell of a machine to run Obduction smoothly in VR. (The same applies to Myst-like adventure Call of the Starseed.) It sounds silly, but especially for a game in the Myst vein that’s mostly about interfacing with strange gizmos there’s something special about doing so in VR. It’s enough to give you vertigo.Īnd like all hand-tracked VR, there’s the novelty that comes with operating machinery with your hands. Ditto for the towering cliffs of Kaptar, stretching down into a cloud-filled void. That iconic little white house with its picket fence? It’s not so little once you have the headset on. As I wrote about during Obduction‘s original Oculus release last year, Obduction in VR gives you a whole different sense of scale. I just spent half an hour doing just that with the Vive, and it’s stunning.