Oceanic crust Oceanic crust Oceanic crust is the uppermost layer of the oceanic portion of a tectonic plate. It is composed of the upper oceanic crust, with pillow lavas and a dike complex, and the lower oceanic crust, composed of troctolite, gabbro and ultramafic cumulates. The crust overlies the solidified and uppermost layer of the mantle. The crust and the solid mantle layer together constitute oceanic lithosphere. Oceanic crust is primarily composed of mafic rocks, or sima, which is rich in iron and magnesium. It is thinner than continental crust, or sial, generally less than 10 kilometers thick; however it is denser,
The Conflict Over the Sovereignty of the Diaoyu Islands -- between Taiwan (ROC), China (PRC), & Japan depth of the Okinawa trough that locates in the east is as deep as 2,717 meters, forming a natural sea boundary with China and the Ryukyu islands. As the geological structure of the Ryukyu Islands belong to "oceanic crust", the Diaoyu Islands are "continental crust" that makes a significant difference in between those two. Also, the Diaoyu Islands has one of the largest scale of continental reef layer that contains an abundant amount of river deposits such as the Yangtze River and the Yellow River, and is therefore potentially rich in oil. The Diaoyu islands are considerably much more strategic