The pelagic zone, also known as the open ocean, is the area of the ocean outside of coastal areas. The open ocean lies over the continental shelf. The seafloor is not included in the open ocean.

Oceanographers believe that abyssal plains are so flat because they are covered with sediments that have been washed off the surface of the continents for thousands of years. On the abyssal plains, these layers of sediment have now covered up any irregularities that may exist in rock of the ocean floor beneath them.

In the third edition, Abyssal was solely the language of the demons from the plane of Shavarath, with the gnolls and sahuagin speaking their own eponymous languages. However, with the consolidation of languages in fourth edition, the gnoll and sahuagin languages were removed, and those two races now speak Abyssal.

Because most of the Madeira Abyssal Plain lies within the Cretaceous Superchron, the oceanic crust underlying it cannot be precisely dated by magnetic striping. However, interpolation between recognised magnetic stripes estimated an age range of about 75 to 105 Ma for the oceanic crust underlying the central sub-basin.

Due to scarcity of oxygen, abyssal plains are inhospitable for organisms that would flourish in the oxygen-enriched waters above. Deep sea coral reefs are mainly found in depths of 3,000 meters and deeper in the abyssal and hadal zones.

Lying between the foot of a continental rise and a mid-ocean ridge, abyssal plains cover more than 50% of the Earth’s surface. They are among the flattest, smoothest and least explored regions on Earth.

The ocean floor is called the abyssal plain. Below the ocean floor, there are a few small deeper areas called ocean trenches. Features rising up from the ocean floor include seamounts, volcanic islands and the mid-oceanic ridges and rises.

Arctic Ocean