Listening 4a Ascolta la prima parte della lezione di un insegnante di scienze alla sua classe e rispondi alle domande. HURRICANES 1 What is the origin of the term hurricane ? . 2 What is a hurricane? . 3 What is its internal part called? . 4 Where can it occur? . 4b Ora ascolta la seconda parte della lezione e scegli l opzione giusta tra le due proposte. Teacher: One of the (0) wore / worst hurricanes happened in 2005 in the U.S.A.: hurricane Katrina (1) hit / it the area of the River Mississippi and the city of New Orleans with winds of 225 km per hour and 5 to 9 m high sea waves. The damages were estimated at over $ 80 (2) million / billion. Hurricanes can only form when the water surface temperatures exceed (3) 27 / 37° C and the surrounding atmosphere is (4) cold / calm. This condition may happen between June and November in the (5) northern / north hemisphere, while in the other hemisphere and in Australia they usually occur from October to May. Student: How does a hurricane form? Teacher: Well, large quantities of water evaporate and condense (6) in / into clouds and rain, releasing heat. (7) This / these heat energy, together with the rotation of the earth, drives a hurricane. When the warm column of air from the sea surface begins to rise, it causes an (8) air / area of low pressure that in turn creates winds. If they (9) rich / reach a speed of 63 km per hour, a tropical storm starts: such storms are given a name and divided into categories, from 1 to 5, according to (10) their / the speed and danger. Hurricanes can continue to grow as long as they are over warm waters, but they rarely persist for more than a few weeks and when they travel inland, their power rapidly diminishes. (Adapted from http://www.newscientist.com) USEFUL WORDS heat = calore; to occur = accadere; to release = rilasciare; speed = velocità; wave = onda. 67