The porcelain layer is attached to the metal and makes the crown look like a regular tooth. In comparison, the all-porcelain or all-ceramic crown does not have the layer of metal as part of the crown. The porcelain itself is what goes onto your tooth.
Quick Answer. An abyssal plain is a deep undersea area created by sediments overlaying a rocky crust, and they are the flattest places on Earth. Abyssal plains cover one-third of the Earth's surface, as much as all land above water, and they sit near continental borders and underwater mountain ranges.
Abyssal zone. The abyssal zone or abyssopelagic is a layer of the pelagic zone of the ocean. Abyss derives from the Greek word á¼Î²ÏÏÏÎ¿Ï, meaning bottomless. At depths of 4,000 to 6,000 metres (13,123 to 19,685 feet), this zone remains in perpetual darkness and never receives daylight.