Descriptionary

striation a scratch or gouge on a rock caused by a passing glacier.

stromatolite forming in shallow water, a short, pillarlike rock made from colonies of microorgan­isms, the oldest-known life-forms in the fossil record, appearing in rocks as old as 3.5 billion years.

talus similar to and sometimes used interchangeably with scree, an accumulation of rocks larger than fist- size, at the foot of cliffs or steep slopes.

tanzanite a rare gem, famous for producing three dif­ferent colors—sapphire, violet, and burgundy—when rotated. Tanzanite is reddish-brown when taken from the ground and turns blue or purplish when heated.

till rocks and gravel deposited by a glacier. A large accumulation of till is known as a moraine.

topaz a valuable gem that comes in a variety of col­ors, including transparent, but the most valuable are yellow-pink and brown. Topaz must be heated and irradiated to produce its famous blue color.

tourmaline a semiprecious stone found in black, brown, violet, and pink colors. It is often found with two different colors.

treated stone any stone that has undergone irradia­tion, heating, or staining to improve its color.

tuff rock composed of compacted volcanic ash, usu­ally no larger than coarse gravel.

turquoise a blue or bluish-green gem, commonly used in Native American jewelry of the Southwest.

vein a rock fracture filled with minerals.

ventifact a rock that has been shaped or polished by windblown materials.

Venus's hair stone see rutilated quartz.

vug a cavity in a rock that sometimes may become lined with minerals, such as quartz.

watermelon tourmaline a form of tourmaline that is red on the inside and green on the outside, and also the reverse.

waxy designating any waxy luster, such as found on a moonstone or turquoise.

xenolith a rock found within a rock, usually occur­ring when magma flows and then hardens over an existing rock.

seas and oceans

(Also see beaches and shores)

abyssal pertaining to the depths of the oceans, the abyss.

abyssal hill a submarine hill reaching 700 meters in height, smaller than seamounts.

abyssal hills province any area of seafloor com­pletely occupied by abyssal hills.

abyssal plain an extensive flat area of the seafloor.

abyssal zone a term originally denoting any depth of ocean beyond the reach of fishermen but now gen­erally recognized as at least 1,000 meters and extend­ing to about 6,000 meters, the beginning of the hadal zone. Contrast with the bathyal zone.

Antarctic Circumpolar Current the world's largest ocean current, it circles the globe and feeds cold water into the Atlantic, Pacific, and Indian Oceans.

bathometer an instrument used to measure the depth of ocean water.

bathyal zone an upper layer of ocean water, extend­ing from 100 meters to about 1,000 meters down (the actual depth varies with local light penetration), marked by a more varied and richer fauna and higher water temperature.

bathymetry the measurement of ocean depths.

bathyscaphe a free-diving, deep-sea research vessel or miniature submarine with a manned observation compartment attached to its underside.

bathysphere a manned, spherical diving chamber lowered by cables.

Beaufort scale a scale in which wind speeds are assigned the code numbers 0 to 12, corresponding to "calm" to "hurricane." At sea, estimates of wind force are often taken from the appearance of the sea by the use of the Douglass sea and swell scale in con­junction with the Beaufort scale.

benthic realm the sea bottom and all the creatures that live on it or within it.

benthic storm a muddying of water extending for hundreds of feet in all directions, caused by powerful eddies swirling over the ocean bottom and stirring up sediments, the underwater equivalent of a sand storm.

benthos the ocean floor and the organisms living on it.

bioluminescence the glow or light emitted from several different types of sea organisms, including some fish at deep levels.

caldron a large, steep-sided, pot-shaped depression in the seafloor.

cold wall the northern boundary of the Gulf Stream, where temperature of the water drops by as much as 18°F outside the stream itself.

continental shelf the submerged shelf of a conti­nent, at its end descending sharply to the seafloor.

Coriolis effect the deflective or curving force explaining the clockwise movements of currents in the Northern Hemisphere and the counterclockwise movements in the Southern Hemisphere.

cross seas a condition occurring when two oppos­ing waves meet head-on and form a towering crest.