How Does Wind Change Earth's Surface?
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How Does Wind Change Earth’s Surface? Wind is a powerful force that changes Earth’s surface Science through weathering, erosion, and deposition. These three Vocabulary processes can create beautiful landscapes and interesting • Dust storm shapes in rock. But wind can also cause damage to plants • windbreak and houses. People can design ways to prevent some of this damage. 1. Wind Causes Weathering and Erosion This is the surface of a sand dune in Death Valley National Park, California. In dry areas, wind is a powerful cause of weathering and erosion. Here the wind is eroding sand between the plants. You learned how water changes Earth’s surface through weathering, erosion, and deposition. Wind also causes these processes. This is especially true in dry, open areas where strong winds are common and a lot of rock is exposed. Think about visiting a dry desert. You observe the landscape and see miles of sand all around you. Where did it come from? Sand is made up of small bits of weathered rocks that are all about the same size. In deserts, wind often causes weathering by blowing sand and other material against cliffs and large rocks. This wears them down and creates more bits of sand and dust. Over time, the rock is scraped and polished away. Wind also has the ability to erode. This is especially true where there are not many plants to protect the ground. When a gust of wind blows, it picks up sand and other bits of material. It carries these bits with it. Wind can carry pieces the size of sand only for short distances at a time. But over time it can move them several kilometers. Tiny pieces like dust can blow thousands of kilometers away. Wind erosion leads to more weathering. The material that the wind carries helps to weather rock that it hits, creating more loose material. In this way, erosion causes more weathering. And weathering causes more erosion. 2. Wind Weathers Rock into Natural Structures Arches National Park has rock in many shapes. Weathering and erosion from wind and gravity helped carve these pillars from solid rock. Grains of sand in a desert are small pieces of evidence of weathering and erosion. Some evidence is much larger, like the Delicate Arch in Utah. It is a large sandstone arch that is 14 meters (almost 46 feet) tall. That is higher than a four- story building! It is shaped like a giant, upside-down U. How did rock become shaped like this? The Delicate Arch and other natural arches were formed because of the dry, windy climate. Later, over long periods of time, strong winds weathered and eroded the rock that was left. When sand is carried by a strong wind, it can weather rocks. On its own, wind cannot cause a lot of damage to rock. But the wind picks up sand and other material. The sand hits against the rock and breaks off tiny pieces. Gravity causes these pieces to fall off, especially when they have been weakened by wind. It takes a lot of time, but the sand in the wind can carve large rocks into interesting shapes. It helped to carve arches out of solid rock! Wind continues to carve new arches. It also keeps carving old ones. The same process that created the arches is slowly working to destroy them. As wind and sand remove more material, each arch keeps getting thinner. Eventually, weathering will remove so much of their support that gravity will make these arches fall. In windy areas, you might see large structures carved from the rock. This one in Arches National Park is called the Delicate Arch. 3. Wind Deposits Material in New Places When wind deposits a lot of sand in one place, it creates hills called sand dunes. Wind continues to move sand dunes even after they are formed. It also creates patterns in sand, like these ripples and waves, that are constantly changing. You learned that material eroded by water is eventually deposited in new places. This happens when the water slows down. The wind eventually slows down too. Sand and dust that are eroded by wind also get deposited in new places. Think about the sandy desert again. Wind eventually deposits sand after blowing it to new places. The sand that you see in the desert was deposited and built up over time. Often, an object such as a rock, plant, or building slows down the wind that runs into it. This contributes to deposition. The size of the pieces of eroded material affects their erosion and deposition. Large pieces such as large grains of sand are too heavy to be lifted high. Most winds can only carry them across the ground for a few centimeters or so at a time. Where the sand is carried and dropped by the wind, it can build up into hills called sand dunes. Some dunes are 400 meters (about 1,300 feet) tall! As long as the wind blows, it carries sand over the ridges of the dunes and deposits it on the other side, where the wind is weaker. In this way, the wind causes sand dunes to move one grain at a time. Some dunes can move about 25 meters (82 feet) every year. Over time, these hills of sand can move many kilometers. 4. Wind Can Transport Material Long Distances Wind blows large amounts of dust from dry areas, like the Sahara in Africa. Dust storms are sometimes so large they can be seen from space and transport dust to other continents. In rivers, the force of water sometimes transports large rocks and even boulders. Wind cannot move pieces that are nearly this large. But wind can move some material much farther than any stream or river. The wind lifts small pieces of dust high into the atmosphere. Some dust blows all the way around the world before it settles! You learned that wind carries sand by bouncing it across the ground a little bit at a time. Sand grains are too heavy to be carried higher. But the wind erodes lighter pieces of material differently. Dust is made up of very small pieces of rock, much smaller than pieces of sand, so it is very light. Wind carries dust high into the sky. Think back to the desert. As wind blew across the ground near Delicate Arch, it eroded the weathered bits of rock. The distance that these bits went depended on their sizes. Larger, heavier pieces of sand were deposited in the same general area, in sand dunes. Other, tiny bits of dust blew high up into the sky. Often, these tiny pieces of dust are deposited very far away by dust storms. A dust storm occurs when a strong wind like a weather front blows dust from a dry region. When dust storms pass through, they can deposit a layer of dust over everything. They also move large amounts of material. Sometimes the dust is blown thousands of kilometers. Sometimes there is so much wind erosion that it creates large dust storms. It can be almost impossible for people and animals inside of the dust storm to see. 5. Wind Erosion Can Cause Damage During the Dust Bowl years, wind deposition caused a lot of damage on the Great Plains. Here, a house is partly buried beneath a giant heap Weathering and erosion caused by wind can create beautiful landscapes like patterns in sand and interesting arches. But sometimes these processes can cause damage. Wind erosion damages plants because bits of flying sand cut their stems and dust covers their leaves. When wind blows away soil, that soil is no longer there for plants to grow in. So, farms and gardens can be severely damaged by wind erosion. Buildings can also be damaged when sand blows against them. Wind can cause even more damage in an area that does not have enough plants. During a drought, many plants die due to lack of water, and the soil is left bare. When wind begins to blow, it can erode away the top layer of soil. This happened in the Great Plains of the United States during the 1930s. For thousands of years, native grasses there protected the soil. They kept it in place. But farmers tilled up the grasses to plant wheat. When a drought came, their crops died and exposed the soil to the wind. The erosion was so bad during that time it was called the Dust Bowl. During the Dust Bowl years, wind eroded so much dry soil it created large dust clouds. Sometimes, these clouds were so thick they blocked out the sun. Sand was deposited in large heaps that buried houses and farming equipment. Millions of people chose to leave their homes. 6. Controlling Damage from Wind Erosion People can prevent much of the damage caused by wind erosion by planting windbreaks in open areas. Windbreaks slow down the wind and prevent flying sand and dust from hitting plants as hard. They can help protect houses as well. Wind erosion can cause serious damage to farms, houses and the environment. The wind blows no matter what. But people can prevent some of the damage it causes. People can learn lessons from events of the past, like the Dust Bowl. It is important not to remove too many native plants in areas that have long droughts. People can choose better places to farm. And they can plant crops in ways that hold onto the valuable topsoil. People can protect farms and houses from wind by making windbreaks along the edges of fields.