DK - WOW! The Visual Encyclopedia of Everything

176

FLOODS

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Heavy rain can swell rivers

until they overflow their

banks, flooding nearby

low-lying land. The water may rise slowly, but it can also surge down valleys in sudden “flash floods” that sweep everything before them. Either way the flood

water can wreck homes and even swamp cities.

TORNADOES

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Thunderclouds are built up

by rising warm, moist air that

spirals up into the cloud.

Sometimes this can develop into a tight, swirling vortex

of rising air, called a tornado.

Wind speeds inside the

vortex can exceed 500 km/h (310 mph), and the powerful

updraft can easily rip the

roof off a house.

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THUNDERSTORMS

Hot sunshine causes water to evaporate and rise into the air, where it cools and forms clouds. Some clouds build up to immense heights of 15 km (9 miles) or more. They contain a huge weight of water that is eventually released in dramatic thunderstorms of torrential rain.

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LIGHTNING

Ice crystals tossed around inside a thundercloud can charge the cloud with electricity like a giant battery. Eventually the charge is released as a colossal spark of lightning, which heats the air along its path to about 30,000°C (50,000°F) in a split second.

HAILSTONES

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Big thunderclouds contain updrafts that

carry raindrops to heights where they

freeze. The pellets of ice fall through the

cloud, but are carried up again so more ice freezes onto them. This can happen many times, building up hailstones that

can be bigger than golf balls.

176_177_Weather.indd 176 03/01/19 12:10 PM