What is "abyssal zone"

Zone \Zone\ (z[=o]n), n. [F. zone, L. zona, Gr. zw`nh; akin to zwnny`nai to gird, Lith. j[*u]sta a girdle, j[*u]sti to gird, Zend y[=a]h.]

1. A girdle; a cincture. [Poetic]

   An embroidered zone surrounds her waist.
   --Dryden.

   Loose were her tresses seen, her zone unbound.
   --Collins.

2. (Geog.) One of the five great divisions of the earth, with respect to latitude and temperature.

   Note: The zones are five: the torrid zone, extending from tropic to tropic 46[deg] 56[min], or 23[deg] 28[min] on each side of the equator; two temperate or variable zones, situated between the tropics and the polar circles; and two frigid zones, situated between the polar circles and the poles.

   Commerce . . . defies every wind, outrides every tempest, and invades.
   --Bancroft.

3. (Math.) The portion of the surface of a sphere included between two parallel planes; the portion of a surface of revolution included between two planes perpendicular to the axis.
   --Davies & Peck (Math. Dict.)

4. (Nat. Hist.)

   1. A band or stripe extending around a body.

   2. A band or area of growth encircling anything; as, a zone of evergreens on a mountain; the zone of animal or vegetable life in the ocean around an island or a continent; the Alpine zone, that part of mountains which is above the limit of tree growth.

5. (Crystallog.) A series of planes having mutually parallel intersections.

6. Circuit; circumference. [R.]
   --Milton.

7. (Biogeography) An area or part of a region characterized by uniform or similar animal and plant life; a life zone; as, Littoral zone, Austral zone, etc.

   Note: The zones, or life zones, commonly recognized for North America are Arctic, Hudsonian, Canadian, Transition, Upper Austral, Lower Austral, and Tropical.

8. (Cryst.) A series of faces whose intersection lines with each other are parallel.

9. (Railroad Econ.)

   1. The aggregate of stations, in whatsoever direction or on whatsoever line of railroad, situated between certain maximum and minimum limits from a point at which a shipment of traffic originates.

   2. Any circular or ring-shaped area within which the street-car companies make no differences of fare.

10. any area to or within which a shipment or transportation cost is constant; specifically, in the United States parcel-post system, any of the areas about any point of shipment for which but one rate of postage is charged for a parcel post shipment from that point. The rate increases from within outwards. The first zone includes the unit of area ``(a quadrangle 30 minutes square)'' in which the place of shipment is situated and the 8 contiguous units; the outer limits of the second to the seventh zones, respectively, are approximately 150, 300, 600, 1000, 1400, and 1800 miles from the point of shipment; the eighth zone includes all units of area outside the seventh zone.

    Abyssal zone. (Phys. Geog.) See under Abyssal.

    Zone axis (Crystallog.), a straight line passing through the center of a crystal, to which all the planes of a given zone are parallel.

Abyssal \A*byss"al\, a. [Cf. Abysmal.] Belonging to, or resembling, an abyss; unfathomable.

Abyssal zone (Phys. Geog.), one of the belts or zones into which Sir E. Forbes divides the bottom of the sea in describing its plants, animals, etc. It is the one furthest from the shore, embracing all beyond one hundred fathoms deep. Hence, abyssal animals, plants, etc.

n. (context geography English) The oceanic realm consisting of the deep ocean, typified by a dearth of plant life, and plentiful carnivorous animals that are able to withstand extreme pressure.

n. the deep sea (2000 meters or more) where there is no light

The abyssal zone or abyssopelagic is a layer of the pelagic zone of the ocean. "Abyss" derives from the Greek word , meaning bottomless. At depths of 4,000 to 6,000 metres (13,123 to 19,685 feet), this zone remains in perpetual darkness and never receives daylight. These regions are also characterised by continuous cold and lack of nutrients.The abyssal zone has temperatures around 2 °C to 3 °C (35 °F to 37 °F) through the large majority of its mass. It is the deeper part of the midnight zone which starts in the bathypelagic waters above. Its permanent inhabitants (for example, Riftia pachyptila, (the giant tube worm) found near hydrothermal vents in the Pacific Ocean and the giant squid are able to withstand the immense pressures of the ocean depths, up to .

The area below the abyssal zone is the sparsely inhabited hadal zone. The zone above is the bathyal zone.