Today’s Wonder of the Day was inspired by adeja. adeja Wonders, “how it sand made” Thanks for WONDERing with us, adeja!

Have you ever visited a beach? If so, you know there’s nothing like a sunny day playing in the waves. Many kids love to build sand castles. Others lie on cozy beach towels and listen to the sounds of the ocean. Have you ever WONDERed where exactly all that sand comes from?

The answer lies in a process called erosion. That’s the slow wearing away of an object by natural forces. In this case, the erosion of rock leads to the sandy beaches enjoyed by people around the world.

In many cases, the process starts with mountains. Forces like wind and water cause mountains to erode over time. The rocks break down into small particles that then travel down streams and rivers until they reach the ocean. Waves and tides erode the rocks and particles further until they become sand. 

Environmentalist and author Rachel Carson summed it up: “In every curving beach, in every grain of sand, there is a story of the Earth.” Sand is part of a cycle—one that often starts far from the shore. Experts say that the sand on every beach on Earth is unique. It tells the story of where it came from, if you know what to look for.

In many cases, you can learn about the makeup of sand from its color. Most beaches are covered in tan sand. But have you ever seen a black sand beach? How about pink or white? These colors all point to different sources of the sand washed up by the waves.

Tan sand is largely made up of quartz tinted by iron oxide. It also contains a substance called feldspar. Black sand contains volcanic material. It comes from eroded lava and basalt rocks. Beaches with black sand are common in areas with volcanic activity.

Where can you find pink sand beaches? They’re located all over the world. This includes Bermuda, the Bahamas, Greece, the Philippines, and Indonesia. The color comes from organisms called foraminifera. These tiny single-celled creatures have red shells and often live in coral reefs.

How about white sand? It often indicates a high level of quartz present in the sand. However, some white sand beaches are actually created by excrement from parrotfish. That’s right—they’re made of fish poop. Parrotfish digest algae and dead coral to create the white sand that forms several of Hawaii’s white beaches.

Today, some experts are trying to predict the future of the world’s beaches. A 2016 study found that 24 percent of sandy beaches have become smaller in the last few decades. One in Texas, along the Gulf of Mexico, lost about 16 feet (15 meters) per year. Another 28 percent, though, have grown. Scientists worry about what this changing landscape could mean for marine species that live near coastlines.

The next time you get to frolic along a sandy beach, think about where all the sand comes from. It may be the result of millions of years of erosion or the product of a parrotfish’s dinner. Either way, sand provides endless fun for many people each year.

Standards: NGSS.ESS2.A, CCRA.L.3, CCRA.L.6, CCRA.R.1, CCRA.R.2, CCRA.R.4, CCRA.R.10, CCRA.SL.1, CCRA.SL.2, CCRA.W.3, CCRA.W.4, CCRA.L.1, CCRA.L.2

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