The Great Atlantic Sargassum Belt is a shockingly large mass of brown algae almost double the width of the American continent, and clearly visible from space.

The first major bloom of the Great Atlantic Sargassum Belt was observed by scientists in 2011. In the almost 15 years since, it has ballooned into a giant mass that stretches 8,850 km and weighs 37.5 million tonnes. It stretches from West Africa all the way to the Gulf of Mexico, forming a massive brown ribbon visible from outer space. Once confined only to the Sargasso Sea, the sargassum belt has been unleashed into the open ocean as it continues to grow because of increased levels of nitrogen and phosphorus in the water.