dense upper cloud
41earth — /errth/, n. 1. (often cap.) the planet third in order from the sun, having an equatorial diameter of 7926 mi. (12,755 km) and a polar diameter of 7900 mi. (12,714 km), a mean distance from the sun of 92.9 million mi. (149.6 million km), and a… …
42comet — cometary /kom i ter ee/, cometic /keuh met ik/, cometical, adj. cometlike, adj. /kom it/, n. Astron. a celestial body moving about the sun, usually in a highly eccentric orbit, consisting of a central mass surrounded by an envelope of dust and… …
43Convection — This figure shows a calculation for thermal convection in the Earth s mantle. Colors closer to red are hot areas and colors closer to blue are cold areas. A hot, less dense lower boundary layer sends plumes of hot material upwards, and likewise,… …
44environment — environmental, adj. environmentally, adv. /en vuy reuhn meuhnt, vuy euhrn /, n. 1. the aggregate of surrounding things, conditions, or influences; surroundings; milieu. 2. Ecol. the air, water, minerals, organisms, and all other external factors… …
45global warming — an increase in the earth s average atmospheric temperature that causes corresponding changes in climate and that may result from the greenhouse effect. [1975 80] * * * Potential increase in global average surface temperatures resulting from… …
46volcano — /vol kay noh/, n., pl. volcanoes, volcanos. 1. a vent in the earth s crust through which lava, steam, ashes, etc., are expelled, either continuously or at irregular intervals. 2. a mountain or hill, usually having a cuplike crater at the summit,… …
47Ice — This article is about water ice. For the broader concept of ices as used in the planetary sciences, see volatiles. For other uses, see Ice (disambiguation) …
48galaxy — /gal euhk see/, n., pl. galaxies. 1. Astron. a. a large system of stars held together by mutual gravitation and isolated from similar systems by vast regions of space. b. (usually cap.) See Milky Way. 2. any large and brilliant or impressive… …
49Uranus — /yoor euh neuhs, yoo ray /, n. 1. Astron. the planet seventh in order from the sun, having an equatorial diameter of 32,600 miles (56,460 km), a mean distance from the sun of 1,784 million miles (2,871 million km), a period of revolution of 84.07 …
50Principal national parks of the world — ▪ Table Principal national parks of the world Africa Europe and Russia Asia North America and the Caribbean Australia and Oceania South America Africa country national park date area description protected status national park status square miles… …
