Transcript Wind
Wind What causes wind? Where does wind come from? Why does the wind blow? What is wind chill? What causes wind? 1. Hot air rises 2. Cold air moves to take its place. 3. Hot air cools and falls down taking the place of the cold air. Why does hot air rise? • Warmer molecules move faster… – Faster molecules hit harder… • Harder collisions mean they bounce away farther… –Farther bounces means more space between molecules… »More space between molecules mean less dense air… • Less dense air rises! Two types of winds… • Global Winds – Form a pattern all over the globe • Local Winds – Happen in isolated areas Why is some air hotter? • Air at the equator is warmer than other air because it receives direct sunlight. • The air at the equator rises and ½ goes north and ½ goes east. • These are called GLOBAL WINDS because they happen all around the globe. What happens on the rest of Earth… • The same rising of warm air happens at 60° N and 60°S. Global Wind Names Doldrums • Where wind rises at the equators • Very little wind blows there. • Long ago ships would get stuck due to the lack of winds – Horse latitudes Trade Winds • Helped to sail European ships to the New World so they could trade. • Northeast Trade Winds are what sailed Columbus to North America Westerlies and Easterlies • Named from where they start. – Westerlies • Blow from west to east – Easterlies • Blow from east to west What about the LOCAL WINDS? • Local winds happen due to unequal heating of the earth. – Due to geography (mountains, valleys, etc…) – Happens over smaller areas than global winds. • Two common types – Land Breeze – Sea Breeze LOCAL WIND KEY POINTS… • The sand… – Heats up quickly. – Cools down quickly. • The Ocean… – Heats up slowly. – Cools down slowly. Land Breeze • Wind that blows from the land to the sea – Named for where it comes from • Happens at night • Warm air over the ocean rises and cool air from the land goes to take its place. Sea Breeze • Wind that blows from sea to land. – Name for where it comes from • Happens during the day. • Warm air over the sand rises and cooler air from the ocean goes to take its place. Wind can cause • Weathering – Breaking down of rock/sand • Erosion – Movement of rock/sand • Deposition – Putting rock/sand in a new place Dust Bowl • Wind storms and drought that went on for about 10 years. • Crops died and land was left bare. • The wind caused lots of erosion of the top soil. • Farmers now use techniques that prevent erosion due to wind because of the dust bowl. – Soil Conservation