Flares have been washing up on beaches for a long time:
an AP news item from February 23, 1993
Last week, several small stones in the pocket of a California woman’s shorts exploded into flame, leaving her with third-degree burns. The stones came from a beach at San Onofre State Beach in San Diego, which she’d visited earlier in the day.
The story caused a sensation, as media discussed what could make rocks catch on fire. By Friday, California environmental health officials had an answer, or at least part of one: two of the rocks were covered in phosphorus, an element that’s known for igniting into a fierce white flame when it’s exposed to air. Near as they can tell, as long as the rocks were wet with seawater, the phosphorus didn’t ignite, but after they’d dried out in the woman’s pockets over the course of the day, the phosphorus reacted explosively.
But how did the rocks get covered with phosphorus? Though the substance is mined and used in fertilizers, it isn’t very common in in the natural world in its explosive form, called white phosphorus. White phosphorous does, however, have a long history of production by militaries, who use it in flares. Unexploded military flares, presumably dropped by aircraft, have been known to wash up on beaches: Just last year flares washed up on a beach a half-hour’s drive from San Onofre. NBC reported that those flares were from military exercises going on off the coast.
The retreat of the ice covering “Snowball Earth” 700 million years ago might have been the key to the Cambrian explosion that seeded our planet with diverse forms of life. But the trigger may not have been the changes to the climate, but rather the release of phosphorus into the ocean.
During this time period, called the Cryogenian or Snowball Earth stage, the entire planet was covered in snow and ice, and the oceans may even have been frozen. Many researchers believe that the ice receded twice during this freezing period, first around 700 million years ago and then again around 635 million years ago. In a paper published in Nature this week, a team of researchers propose that these receding sheets released phosphorus into the oceans.
In the scheme offered by [Noah] Planavsky and his colleagues, the snowball ice sheets would, as their modern counterparts do, grind up continental rock that would release phosphorus when the glaciers retreated. That phosphorus would wash into the ocean, where it would fertilize algal blooms that could drive a surge in the production of organic matter and oxygen. And the added organic matter that settled into the mud on the ocean bottom would leave additional oxygen behind, eventually boosting atmospheric and oceanic oxygen. [ScienceNOW]