sapphire a precious gem; a blue lustrous variety of corundum. Sapphires in colors other than blue are known as fancy sapphires.
scoria a porous volcanic rock.
scree gravel and small rocks that pile up at the foot of cliffs or steep slopes. Sometimes used interchangeably with talus.
sedimentary rock rock made by settled mud, silt, sand, cobbles, pebbles, and organic matter, forming layers or "strata."
shale a fine-grained, sedimentary rock formed by compaction in water.
shocked quartz quartz that has become deformed due to massive pressure, as occurs around a nuclear detonation or a meteorite impact. Scientists use shocked quartz to verify that craters around the Earth were formed by meteorite impacts and not volcanic activity.
silica silicon dioxide, a mineral widely found in sand, quartz, and agate, used in the manufacture of glass.
skarn a metamorphic rock varied in color and containing a mix of minerals, including garnet, pyroxene, magnetite, and others.
slate a fine-grained, metamorphic rock made up of quartz, muscovite, and other minerals; it is famous for its use in roofing shingles.
soapstone a soft rock composed of talc, serpentine, and magnetite and recognized by its soapy feel.
star sapphire a sapphire with inclusions of rutile needles, creating asterisms.
strata layers or beds of rock.
stratification the layering of sedimentary rock.
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.
dead water a body of water, particularly common in the fjords and seas of Scandinavia, that mysteriously slows or nearly stops the forward progress of ships; thought to be caused by a thin layer of freshwater floating above a layer of denser, salty water that, when mixed, creates a train of slow-moving, submerged waves that exert a powerful drag on vessels passing over it.
deep a deep-sea plain within a large basin.
deep-scattering layer a large body of free-swimming sea organisms, such as fish or squid, that confuses sonar readings by creating a "false bottom" or false seafloor.
doldrums equatorial ocean regions characterized by flat, calm seas and little or no wind.
Douglass sea and swell scale a scale of numbers assigned to descriptive terms (0 = calm, 8 = precipitous, 9 = confused, etc.) to denote the sea's state with a second scale of numbers (0 to 99) to denote low to heavy swells.
eddy a swirling current running contrary to the main current; may be caused by two currents meeting head-on or side-long.