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.
Most of the ocean floor is a huge, dark, nearly flat area called the Abyssal Plain. The sea floor is a huge flat area. It lies at depths of about 4000 to 6000 meters below the surface of the ocean. It is called the Abyssal Plain. Sea floor spreading occurs here, which means that there is volcanic action and a mid-ocean ridge where some of the lava has cooled.