That portion of the atmosphere from the earth’s surface to the tropopause, that is, the lowest 10 to 20 kilometers of the atmosphere.
A relatively thin body of sand or sandstone covering a large area. Also known as sheet sand.
Dark-colored, referring to igneous rock containing at least 50-60% mafic minerals. Also known as chromocratic; melanic.
Half the arithmetical sum of the latitudes of two places on the same side of the equator; mean latitude is labeled N or S to indicate whether it is north or south of the equator.
The formation of a continuous ice cover on a body of water.
A measure of the precipitation effectiveness or aridity of a region, given by the following relationship: index of aridity = P/(T + 10), where P is the annual precipitation in centimeters, and T the annual mean temperature in degrees Celsius.
See wandering dune.
Garnet is a widely distributed group with several minerals. They are found in both metamorphic and igneous rocks. The chief use of red transparent garnets are as an inexpensive gem stone, however, much is used as an abrasive materal. They have the formulae A3B2(SiO4)3 and a relative hardness of 8. The commonest colour of garnet is red and the luster is vitreous. The dodecahedron and trapezohedron are the common forms. There are also white, green, yellow, brown, and black varieties. The garnet is a silicate, the bases being aluminia lime (grossularite, essonite, or cinnamon stone), or aluminia magnesia (pyrope), or aluminia iron (almandine), or aluminia manganese (spessartite), or iron lime (common garnet, melanite, allochroite), or chromium lime (ouvarovite, the colour emerald green). The garnet was, in part, the carbuncle of the ancients. Garnet is a very common mineral in gneiss and mica slate.
See right way up.