What is an abyssal plain?

Abyssal plains are among the most level places on Earth, formed where fine sediments slowly blanket older seafloor and smooth out the rough volcanic crust beneath. They are especially extensive in the Atlantic Ocean, where sediment supply from continents has had millions of years to accumulate. Despite their name, they are not lifeless: these deep regions support microbes, worms, crustaceans, and other animals adapted to cold, high-pressure conditions. The first detailed mapping of abyssal plains expanded greatly after mid-20th-century sonar surveys and deep-sea expeditions.