- Who
- Abyssal plains
- What
- 40 percentage
- Where
- Not Applicable ()
- When
- 2006
Abyssal plains are vast expanses of flat, featureless terrain found at the deepest parts of the ocean. They cover approximately 40% of the ocean floor at depths of 4,000–5,000 m (13,000–20,000 ft). The uniform flatness is caused by the accumulation of sediments, up to 5 km (3 miles) thick in places, which overlies the basaltic rocks of the oceanic crust. This means that there is less than 1.5 m (5 ft) of vertical variation for every mile, with an overall average gradient of 1:1,000.
