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Sea Foam Delights Visitors of Lebanese Beach

Last week, thick white layers of bubbles washed ashore Naqoura Beach

(Sarah Salman)
smithsonian.com

Last week, Naqoura beach​, in Lebanon, looked as if snow had come to the hot Mediterranean climate. But the frothy white beaches aren't blanketed in frozen water. As Nourhan Nassar reports for Stepfeed, they're covered in sea foam.

This excessive amount of sea foam isn’t a unique phenomenon. Waves of fluffy white stuff have periodically delighted visitors at coastlines from Australia to Blackpool, England. But why do waterways seem to occasionally bubble over? And, more importantly, is it dangerous?

Sea foam is created by the combination of air, water, and surfactant, Emily Elert reported for Popular Science in 2012, after sea foam blanketed the beaches of The Rockaways ​Peninsula in New York. A surfactant is “a kind of sticky molecule that clings to the surface between water and air,” she wrote.

Under normal conditions, the high surface tension of the water prevents bubbles from sticking around. Any bubbles in the water caused by a crashing wave usually pop as soon as they reach the surface. But surfactants lower surface tension, which means that a rising bubble doesn't immediately burst. Instead, it stretches the surface, trapping the air inside, writes J. Wallace Gwynn for the Utah Geological Survey.

Though human-created pollutants like fertilizer or soap can act as surfactants, there are many naturally occurring surfactants in waterways, which form from a range of compounds like fats from algae, seaweed and decomposing fish. Though these may seem like vastly different compounds, all have one end that is attracted to water and another that repels it. 

When intense agitation whips up waterway, it causes these molecules to line up with their water-loving sides facing to the ocean and the water-repelled end dangling towards the atmosphere. As Elert​ writes, they can even line up back to back—their water loving sides separated by a thin layer of water, which makes the outer curve of the bubble. “The bubble’s surface can remain stretched for long periods of time, and as millions of bubbles form, they build up into deep piles of long-lasting foam,” writes Wallace Gwynn.

It takes a large amount of surfactants—like from algae blooms or pollution plumes—or extreme agitation to create truly large amounts of foam. Severe storms like Eleanor that hit the United Kingdom earlier this month (or the storms that hit Queensland, Australia in 2016) can also produce epic baths of fluff.

While sea foam is usually harmless, it can occasionally be a problem. During red tides—blooms of the toxic algae Karenia brevis—the popping sea foam bubbles can create an aerosol that irritates eyes and respiratory pathways. Blooms of Akashiwo sanguinea algae can also disrupt the protective waterproof coating on birds. This makes it hard for them to keep warm as if the birds had been caught in an oil spill.

As for Naqoura beach in Lebanon? According to Nassar, rough conditions are to blame for the latest frothing event. And though the foam has likely disappeared from Naqoura, it'll surely pop up somewhere else soon.

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