Missing Ocean Crust?

Pillow basalts on the ocean seafloor. Pillow basalts commonly are found at the surface of the seafloor, especially at mid-ocean ridges. There’s no pillow basalts at one place in the Atlantic Ocean, though. At this place the Earth’s mantle is exposed!  

As a marine geologist, I am somewhat stunned to read this article about missing ocean crust. What is going on here? Is the mantle really exposed? Did massive faulting just mantle rocks?

Tomorrow, I head down to Woods Hole Oceanographic Institution for my biweekly marine geology class and my weekly seafloor petrology lab. You can bet I’m going to be asking my instructors– as well as any other marine geologists I happen to run across– plenty of questions about this article and expedition!


Evelyn is a geologist, writer, traveler, and skeptic residing in Cape Town, South Africa with frequent trips back to the US for work. She has two adorable cats; enjoys hiking, rock climbing, and kayaking; and has a very large rock collection. You can follow her on twitter @GeoEvelyn. She also writes a geology blog called Georneys.

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  1. Can you explain the difference between crust and mantle as it pertains to this region of the ocean floor? I've never studied geology, but my layman's understand of plate tectonics is that tectonic plates move due to a kind of upwelling at one end and subduction at the other, so fresh rock is being brought up all the time, and cooling to form new crust. So I would expect some of the sea floor to be "not quite crust yet" around the upwelling region and then gradually become crust as it moves outward. So what is it about this area that makes it mantle as opposed to crust? What's so uncrusty about it?

  2. Very interesting. As they say, unexpected according to the Plate Tectonic model. Always exciting when big theories are challenged.


    You can find some answers here:

    The crustiness has something to do with chemistry, if I got that right.

    Unfortunately the article doesn't say much about the hole itself, for example I'd like to know where they found it and how big it is. The good news is that we'll be able to get mantle samples without drilling through 5-10 km of ocean floor.

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