boundary contrast
51arctic — arctically, adv. /ahrk tik/ or, esp. for 7, /ahr tik/, adj. 1. (often cap.) of, pertaining to, or located at or near the North Pole: the arctic region. 2. coming from the North Pole or the arctic region: an arctic wind. 3. characteristic of the… …
52Atlantic Ocean — an ocean bounded by North America and South America in the Western Hemisphere and by Europe and Africa in the Eastern Hemisphere. ab. 31,530,000 sq. mi. (81,663,000 sq. km); with connecting seas ab. 41,000,000 sq. mi. (106,100,000 sq. km);… …
53Pacific Ocean — an ocean bordered by the American continents, Asia, and Australia: largest ocean in the world; divided by the equator into the North Pacific and the South Pacific. 70,000,000 sq. mi. (181,300,000 sq. km); greatest known depth, 35,433 ft. (10,800… …
54Oceanic trench — Oceanic crust is formed at an oceanic ridge, while the lithosphere is subducted back into the asthenosphere at trenches. The oceanic trenches are hemispheric scale long but narrow topographic depressions of the sea floor. They are also the… …
55river — river1 riverless, adj. riverlike, adj. /riv euhr/, n. 1. a natural stream of water of fairly large size flowing in a definite course or channel or series of diverging and converging channels. 2. a similar stream of something other than water: a… …
56tornado — tornadic /tawr nad ik, nay dik/, adj. tornadolike, adj. /tawr nay doh/, n., pl. tornadoes, tornados. 1. a localized, violently destructive windstorm occurring over land, esp. in the Middle West, and characterized by a long, funnel shaped cloud… …
57pre-Columbian civilizations — Introduction the aboriginal American Indian (Mesoamerican Indian) cultures that evolved in Meso America (part of Mexico and Central America) and the Andean region (western South America) prior to Spanish exploration and conquest in the 16th …
58Africa — /af ri keuh/, n. 1. a continent S of Europe and between the Atlantic and Indian oceans. 551,000,000; ab. 11,700,000 sq. mi. (30,303,000 sq. km). adj. 2. African. * * * I Second largest continent on Earth. It is bounded by the Mediterranean Sea,… …
59Iraq — /i rak , i rahk /, n. a republic in SW Asia, N of Saudi Arabia and W of Iran, centering in the Tigris Euphrates basin of Mesopotamia. 22,219,289; 172,000 sq. mi. (445,480 sq. km). Cap.: Baghdad. Also, Irak. * * * Iraq Introduction Iraq Background …
60Thailand — /tuy land , leuhnd/, n. 1. Formerly, Siam. a kingdom in SE Asia: official name of Siam 1939 45 and since 1949. 59,450,818; 198,242 sq. mi. (513,445 sq. km). Cap.: Bangkok. 2. Gulf of. Also called Gulf of Siam. an arm of the South China Sea, S of… …
