I am often asked why we have traveled out to the Hess Deep, why not just drill for gabbro closer to land? There are several layers of rock that make up the oceanic crust,gabbro is one of the lower ones. Other expeditions have tried to drill through all the layers to get to the gabbro, this is very time consuming and difficult. At the Hess Deep a geological fault means that we can drill directly into the gabbro, bypassing the other layers. See cake for further illustration!