![]() ![]() We returned for our second visit to Palmer Station, arriving as planned on the morning of Nov. In any case, everyone headed into Punta Arenas for some land-based R&R. The science teams were allowed to stay onboard the LMG for the night, but some of us had reservations for nearby hotels (Fig. ANTARCTICA FLASHFROZEN FREEAfter the ship was cleared through Chilean customs, we were free to disembark. We pulled up to the dock in Punta Areanas about 10:00 AM on Dec. Wind speed gusted over 50 kts (left) and wave heights were over 5 m (right) during our crossing of Drake Passage on 29-30 November 2011. By morning, we reached the Straits of Maire (Isla de Estados), where we were more protected from the winds and waves, and conditions improved.įigure 1. Winds gusted over 50 kts and we pitched and rolled our way into the wind and through 5 m swells (Fig. ![]() But by the afternoon of Nov 30th, it was clear that we were in for a usual Drake crossing. With good weather holding, the LMG got underway for Punta Arenas about 12:00 Noon.įor a short while, we thought the Drake Passage would lie down for our transit. ![]() 30th, we left Palmer Station and headed for King George Island and the NOAA field camp, dubbed Copabanga, where we were able to go ashore and see dense penguin colonies (with all three species - Gentoos, Adelies, and Chinstraps - apparently co-existing), while we hauled trash and propane tanks from the field camp. Meanwhile, understanding the nature of these ancient glaciations could help scientists dealing with climate change today: "I think one of the biggest messages that Snowball Earth can send humanity," Dehler says, "is that it shows the Earth's capabilities to change in extreme ways on short and longer time scales.On Nov. But, she adds, they might be out there "waiting to be discovered." To do that, scientists would need to find datable volcanic rocks from other parts of the world, which are about "as common as unicorns," she jokes. However, because the two new samples come from southern China, they don't paint a global picture of the ancient thaw, says Carol Dehler, a geologist at Utah State University in Logan. Because previously discovered samples have error bars of several million years or more, Xiao says these new dates are the first that can be used to calculate the pace of melting with any certainty. Those error bars essentially bracket the period in which the cap carbonates formed-and, thus, bound the period of the final Snowball Earth thawing event. The key, Xiao explains, is that these two dates are far more precise than those of past samples, with error bars of less than 1 million years. Together, the two samples suggest the melting event was a quick thaw of about 1 million years, Xiao and his colleagues wrote last month in Geology. They were dated to 635.2 million years, give or take 570,000 years. But in 2005, a different team of scientists dated volcanic rocks from above a similar cap at a different location-in China's Guizhou province. Alone, this single new date couldn't reveal the speed at which the melting happened. Using radiometric dating techniques, the team found the volcanic rocks were 634.6 million years old, give or take about 880,000 years. These were embedded below another kind of rock called a cap carbonate-unique deposits of limestone and dolostone that formed during Snowball Earth's shutdown in response to high levels of carbon dioxide in the atmosphere. To shine light on the pace of deglaciation, Xiao and colleagues dated volcanic rocks from southern China's Yunnan province. Although the team doesn't know for certain what caused it, carbon dioxide emitted by ancient volcanoes may have triggered a greenhouse event, causing the ice sheets to thaw rapidly. That's the blink of an eye in our planet's 4.56-billion-year history, suggesting the globe reached a sudden tipping point, Xiao says. The ice, which built up over several thousand years, "melted in no more than 1 million years," says Shuhai Xiao, a paleobiologist at Virginia Polytechnic Institute and State University in Blacksburg who was part of the team that made the discovery. Now, scientists have found that the final snowball episode likely ended in a flash about 635 million years ago-a geologically fast event that may have implications for today's human-driven global warming. ![]() Glaciers blanketed the globe all the way to the equator in one of the mysterious "Snowball Earth" events geologists think occurred at least twice in Earth's ancient past. More than half a billion years ago, our planet was a giant snowball hurtling through space. ![]()
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