"There's a crazy contrast between these delicate, glass-shelled organisms and one of the most powerful eruptions in Earth's history," said lead study author Alexa Van Eaton, a postdoctoral scholar at both the Cascades Volcano Observatory in Washington and Arizona State University.
The diatoms were launched by the Taupo super-eruption on New Zealand's North Island 25,000 years ago. More than 600 million cubic meters (20 billion cubic feet) of diatoms from a lake flew into the air, Van Eaton reported Sept. 6 in the journal Geology. Lumped together, the microscopic cells speckled throughout Taupo's ash layers would make a pile as big as Hawaii's famed Diamond Head volcanic cone.
Some diatoms drifted as far as the Chatham Islands, 525 miles (850 kilometers) east of New Zealand. "They just hitched a ride," Van Eaton said. The pristine shells in the Chatham Island ash suggest diatoms could infect new niches by coasting on atmospheric currents.
"If they made it there alive, this is one way microorganisms can travel and meet each other," Van Eaton told LiveScience's OurAmazingPlanet. "We know that ash from smaller events easily travels around the world."
Diatoms, a golden brown algae, rule Earth's waterways. From Antarctica's glacial lakes to acidic hot springs to unkempt home aquariums, diatoms are everywhere. It's a good thing. The tiny creatures pump out up to 50 percent of the planet's oxygen, said Edward Theriot, a diatom expert and evolutionary biologist at the University of Texas at Austin, who was not involved in the study.
The algae look like little petri dishes or footballs, depending on the species, and spend most of their lives drifting on currents. How diatoms manage to colonize new homes remains a mystery: They can't swim.
Yet diatoms get around. When Wyoming's Yellowstone Lake emerged from its mile-thick ice cover 14,000 years ago, diatoms quickly arrived, Theriot said. "They had to be blown in by some mechanism or carried in by water birds," he added.
Diatoms particularly love volcanic lakes, because they are the only creatures that build shells of glass. (Glass sponges, for instance, produce a skeleton of glass spicules — tiny spike-like structures — but not a hard shell.) Silica-rich magma often causes the volcanic explosions that leave behind lake-filled craters, and silica is the key ingredient in diatom shells. Yellowstone Lake, which sits in a caldera created by a super-eruption, contains so many diatoms that the lake sediments are mostly shells (85 percent by weight), Theriot said.
Now scientists know what happens to diatoms when a massive volcano like Yellowstone blasts through a big lake.
The Taupo Volcano super-eruption slammed through a deep lake that filled a rift valley, similar to the elongated lakes in East Africa. The combination of water and ash created a hellish dirty thunderstorm, with towering clouds and roaring winds. The detonation flung ash and algae upward at more than 250 mph (400 km/h), Van Eaton said. Volcanic hail (called accretionary lapilli) pelted the landscape for miles.
Van Eaton discovered the diatoms while examining the volcanic hail with a scanning electron microscope.
"The first time I ever saw them I was looking at these volcanic ash aggregates and, bam, these gorgeous little symmetrical shells were there," she said. "Their shells are immaculately preserved."
Van Eaton soon determined that one of the three diatom species entombed in the ash only lives on the North Island of New Zealand. This meant she could track the 25,000-year-old ash layers around the South Pacific with a unique biologic marker. The unique North Island diatoms turned up in a few inches of ash on the Chatham Islands. The diatoms' trip to the Chatham Islands took longer than it looks on a map. The prevailing winds blew west at the time, so the shells circled the Southern Hemisphere before landing on the islands, Van Eaton and her colleagues deduce.
Some of the diatoms even kept their color, both in ash close to the volcano and at the Chatham Islands. The color suggests they weren't cooked to extreme temperatures in the volcanic eruption, Van Eaton said.
Read more at Discovery News
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