sand dune
Reading Passage 1
Wind can change Earth’s surface over time. One landform wind can build is a sand dune. The process starts with weathering, which breaks rocks into small pieces of sand. These tiny pieces are light and easy to move.
Wind moves sand from one place to another. This movement is called erosion. When the wind slows down, it drops the sand. This is called deposition. When sand is dropped in the same place again and again, it begins to pile up.
You might see this on a playground. After a windy day, sand collects in the corners or against a fence. Over time, the sand forms a mound.
In deserts and near beaches, the same thing happens. Wind causes erosion by moving sand and deposition by dropping it. As layers build up, a sand dune forms. Grasses can begin to grow on the dune. Their roots hold the sand in place and reduce erosion, even though strong winds can still change the dune slowly.
Reading Passage 2
Wind is a powerful force that can slowly change Earth’s surface. Over time, wind helps form landforms such as a sand dune. This process begins with weathering, which breaks larger rocks into smaller pieces of sand. Heat, water, and other natural forces weaken rocks until they crumble into tiny grains.
Once sand is formed, wind can move it. This movement is called erosion. When wind blows across a dry surface, it picks up loose sand and carries it to a new location. Stronger winds can move more sand, while gentle winds move only small amounts.
Eventually, the wind slows down. When this happens, it can no longer carry the sand. The sand falls and settles in a new place. This process is called deposition. As more sand is dropped in the same area, the pile begins to grow taller and wider.
You may have seen something similar on a playground. After a windy day, sand often collects in the corners of the play area or against a fence. The wind moves the sand across the ground and drops it where it cannot travel any farther. Over time, that collected sand forms a small mound.
In deserts and along beaches, this same process continues again and again. Wind causes erosion by moving sand and deposition by dropping it. As layers build up over many days, months, or even years, a sand dune forms. After a dune begins to grow, grasses may start to grow on it. The roots of these grasses hold the sand in place and reduce further erosion. Strong seasonal winds can still reshape dunes or create new ones, but plants can help slow these changes.
Reading Passage 3
Wind is a significant force that reshapes Earth’s surface over time. One example of a landform created by wind is a sand dune. The process begins with weathering, which breaks solid rock into smaller particles of sand. Temperature changes, water, and other natural forces gradually weaken rock until it separates into loose grains.
After sand forms, wind transports it across the surface. This transport process is known as erosion. Wind speed and direction influence how far and how much sand is moved. When the wind loses energy, it can no longer carry the particles.
At that point, the sand settles to the ground. This settling process is called deposition. If sand continues to be deposited in the same location, layers begin to accumulate. Over time, these layers increase in height and width.
This pattern can be observed on a playground after a windy day. Sand often gathers in corners or along barriers where wind slows down. The same cause-and-effect process happens on a much larger scale in deserts and coastal areas.
Repeated cycles of erosion and deposition build up a sand dune. As the dune develops, grasses may begin to grow across its surface. The roots of these plants anchor the sand and decrease the rate of erosion. Although strong seasonal winds can reshape existing dunes or create new ones, plant growth can stabilize parts of the landform.