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.
[Origin of the word: Gr. abussos â âbottomlessâ â âaâ = without + âbussosâ = depth]. This zone is usually where the continental slope levels off. More than 30 percent of the bottom of the ocean is said to be situated here. General depth range of the Abyssopelagic Zone: 4000 â 6000 meters.