The abyssal zone or abyssopelagic zone is a layer of the pelagic zone of the ocean. 'Abyss' derives from the Greek word ἄβυσσος, meaning bottomless. At depths of 4,000 to 6,000 metres, this zone remains in perpetual darkness. It covers 83% of the total area of the ocean and 60% of Earth's surface. The abyssal zone has temperatures around 2 to 3 °C through the large majority of its mass. Due to there being no light, there are no plants producing oxygen, which primarily comes from ice that had melted long ago from the polar regions. The water along the seafloor of this zone is actually devoid of oxygen, resulting in a death trap for organisms unable to quickly return to the oxygen-enriched water above. This region also contains a much higher concentration of nutrient salts, like nitrogen, phosphorus, and silica, due to the large amount of dead organic material that drifts down from the above ocean zones and decomposes. The water pressure can reach up to 76 megapascal.
The area below the abyssal zone is the sparsely inhabited hadal zone. The zone above is the bathyal zone.