LESSON 9.8 What are the causes and impacts of hydrometeorological hazards?
LEARNING INTENTION By the end of this lesson you should be able to: • explain the causes of a hydrometeorological hazard • explain the impacts of the hazard
Tune in Both of the images in FIGURE1 show volcanic eruptions. One image shows a hazard, and one image shows a disaster. FIGURE1 Hazard or disaster?
Identify the hazard and the disaster. Justify your answer.
9.8.1 How does weather change? The Earth is surrounded by gases called the atmosphere. It protects us from the sun’s heat and the chill of space, creating the conditions that support life. The atmosphere has five layers (see FIGURE2 ). The troposphere is the layer from ground level up to 16 km. All our weather happens in this layer due to constant changes in the air. Extreme weather events, like droughts, floods, cyclones, snow and heatwaves, all start in the troposphere. This layer has most of the water vapour, linking it to precipitation (rain, snow, hail). Weather comes from three factors: temperature, air movement and water in the air. The sun affects themall. First, the sun heats the air and Earth’s surface, which heats the air more. How hot it gets depends on the season and cloud cover. Second, the sun makes air move. Warm air rises, and cooler air moves in. Third, the sun creates moisture in the air by causing water to evaporate, forming clouds, which can become rain, snow, or hail. These three factors can cause extreme weather, such as heatwaves, cyclones or floods.
TOPIC9 Water in the world 291
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