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.
And the word 'plain' usually means a flat, wide area. Put those two things together and you have an abyssal plain, which refers to the huge, flat areas on the ocean floor. Flat is almost an understatement. The abyssal plains are some of the flattest features on the planet.Some drop in elevation less than a foot for every 1,000 feet in distance.f you have no idea what an abyssal plain is, your imagination is likely to come up with some depressing images ('abyssal' sounds pretty close to 'abysmal,' after all). Here you will learn what an abyssal plain actually is, what it looks like and what lives there.