tailieunhanh - EARTH Phần 8

Trái Đất là một hành tinh đất đá, khác với những hành tinh khí khổng lồ như sao Mộc. Trái Đất là hành tinh lớn nhất trong bốn hành tinh đất đá của hệ Mặt Trời, về cả kích thước và khối lượng. Trong bốn hành tinh này, Trái Đất có độ đặc lớn nhất, hấp dẫn bề mặt lớn nhất, từ trường mạnh nhất, tốc độ quay nhanh nhất. | EXTREME WEATHER Wcftk Ofbbl Wo th r tZnơ-F r aĩ 90 Intense solar heating can cause very high evaporation rates that make warm moist air rise unusually fast. This builds up huge cumulonimbus clouds that cause thunderstorms and hail and creates conditions of extremely low pressure. Air swirls into the low-pressure zone creating a deep depression with very strong winds. In tropical oceans intense heating generates hurricanes. In extreme cases the updrafts can give rise to the destructive vortex of a tornado. HAILSTORMS The giant cumulonimbus clouds that cause thunderstorms are built up by powerful air currents with vertical speeds of 100 mph 160 kph or more. Ice crystals hurled around by the turbulent air pick up water that freezes onto them and if they are tossed up and down enough this builds up layer after layer of ice to form hailstones. If the air currents are strong enough they can create huge and very dangerous hailstones like these. TORNADOES These terrifying events are caused by air swirling into the base of a very vigorous storm cloud and spiraling upward. The updrafts are powerful enough to rip houses apart and the winds around such tornadoes are the most powerful ever recorded reaching at least 318 mph 512 kph on one occasion. 91 Updraft can reach 150 mph 240 kph Narrow funnel cloud extends down to ground level STORM SURGE During a hurricane the converging winds and extremely low air pressure over the ocean build up a hump of water or storm surge. This can sweep over the land like a tsunami and causes massive devastation. A storm surge almost destroyed New Orleans in 2005 and killed at least 150 000 people in Burma Myanmar in 2008. WATERSPOUTS Tornadoes can develop over seas and large lakes especially in the tropics and subtropics. The powerful upcurrents spiraling up into the cloud draw water up with them so they are known as waterspouts. They are usually less violent than tornadoes but a waterspout is strong enough to easily capsize a boat. It is most .