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 Call of Earth The Call of Earth The Call of Earth (1992) is a science fiction novel by American writer Orson Scott Card. It the second book of the Homecoming Saga, a fictionalization of the first few hundred years recorded in the Book of Mormon. The book focuses on several key events that happen after Nafai, Elemak, Issib, Mebbekew, Zdorab and the father Volemak leave for the desert. Elemak has a dream from the Oversoul, foretelling Volemak's sons going back to the city of Basilica to get wives. The sons proceed to Nafai's and Issib's mother, Rasa, who is attempting to keep order