Decline of Sea Glass: Trash-Turned-Treasure Fragments Become Harder To Find Due to Proliferation of Single-Use Plastic

On beaches along bodies of saltwater, colorful bits of worn glass can be found mixed in with the sand. These frosted fragments, known as sea glass, could decline due to the proliferation of single-use plastics.

Creation of Sea Glass

All glass begins as sand, mainly quartz sand. In making glass from sand, refiners purify their quartz sand using physical and chemical processes to remove all minerals, leaving only quartz behind. The remaining quartz sand is then molten and added with soda ash and limestone for increased malleability and glass strength. This mixture is then reformed into windows, bowls, bottles, and more.

Glass was the popular container before the proliferation of single-use plastic started. After the glass containers served their purpose, users normally throw them into a dump. Before the environmental movements of the 1960s, trash dumps in the U.S. were commonly left open and exposed to rain and wind. Since these dumps are situated near waterways or coves, the trash, including the glass bottles, is washed by the runoff until it ends up in the ocean.

As they travel toward the ocean, glass bottles run into rocks and other objects, breaking them into smaller pieces. When the fractured containers travel close enough to the coast, high tides and incoming waves wash them out to the sea. Meanwhile, these fragments could slide and roll along the sandy seafloor due to wave action. From this movement, the sharp edges of the glass turn round, and its once smooth and clear glass shows a pitted, frosted appearance.

Since quartz is the foundation of all glass materials, many of its properties are reflected in sea glass. These include clarity, which explains why quartz is nearly translucent. Quartz also fractures or breaks in a special way called a conchoidal fracture. This explains why sea glass tends to break into smaller pieces but does not quickly weather away.

Most sea glass spends a few decades on the seafloor, where it gets tossed around and smoothened in sand. There are also pieces of sea glass estimated to be hundreds of years old since the hardiness of quartz allows them to persist in the environment for such a long time.

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Dwindling Sea Treasures

These gifts from the sea have been exciting to environmental science professor Lori Weeden from Kennedy College of Sciences. She has analyzed sand from across the world and added samples into a collection for the environmental, earth, and atmospheric sciences at the University of Massachusetts Lowell. Her studies reveal how sea glass washes up on beaches reflects the connection between human activity and Earth's natural processes.

Weeden discovered that as single-use plastics become more popular as alternatives to glass bottles, sea glass may become harder to find since there is less glass and more plastic in the supply chain. Because of this, some retailers prefer to create their artificial sea glass using rock tumblers and chemicals.

Compared to the plastic recycling industry, there are not many markets for recycled glass; it is also heavy and difficult to transport. Unless adequately recycled, the discarded glass will continue to provide sea glass for future generations to discover.