Feb. 17, 2009 -- As agents of extinction, comet and asteroid impacts may be losing their punch. According to a new theory about how mass dyings work, cosmic collisions generally aren't enough to cause a major extinction event. To be truly devastating, they must be accompanied by another event that inflicts long-term suffering, like runaway climate change due to massive volcanic eruptions. In other words, a comet couldn't have killed the dinosaurs by itself -- unless they were already endangered species. This kind of one-two punch could explain more than the extinction of dinosaurs, Nan Arens of Hobart and William Smith Colleges said. In a recent paper in the journal Paleobiology, she and colleague Ian West argue that there are two types of events that can cause extinctions -- "pulses" (quick, deadly shocks, like comets) and "presses" (drawn-out stresses that push ecosystems to the brink but may not kill outright, like million-year-long volcanic eruptions). The chances of mass dyings go way up when both happen together, argues Arens. Related Content:
But are all mass extinctions created equal? Can researchers come up with a "Grand Unified Theory" of ancient apocalypse? West and Arens think so. They combed the last 300 million years of geologic record, noting impact craters, massive eruptions, periods of ancient climate change, and then comparing them to extinctions. The rate at which species die off spiked dramatically, they found, when a "pulse"-type event occurred within a million years or so of a "press." The theory fits well for the dinosaurs. Around the time of their demise 65 million years ago, a comet slammed into the Yucatan Peninsula and a huge volcano, the Deccan Traps, was erupting in what is today India. But other extinctions are problematic. The greatest dying in geologic history, the Permian-Triassic extinction, killed 90 percent of all life on Earth, but there is no record of an impact. Instead, all signs point to a 200,000-year-long volcanic eruption in Siberia as the murder weapon. Get More NewsSpiders, Scorpions Among World's Oldest CreaturesMany creepy crawlies have been on Earth much longer than previously believed.Blood-Sucking Vampire Bats Sing DuetsWhite-winged vampire bats "harmonize" with separated roost mates.Oldest Hebrew Writing Possibly FoundAncient inscriptions on a 3,000-year-old pottery shard could make history.Rare, Prehistoric-Age Reptile Found in N.Z.A tuatara has been spotted on the New Zealand mainland for the first time in 200 years.Iceman Has No Living RelativesOetzi, the 5,300 year-old frozen mummy, left no living genetic legacy.SLIDE SHOW: Landscapes of TerrorWhat makes a place feel scary? There are scientific explanations.It's Official: People Are Warming the PolesHumans are conclusively to blame for polar warming, say scientists.Eight-Armed Animal Preceded DinosaursWhat may be one of Earth's first animals was no bigger than a coaster and had eight arms.Phoenicians Live on in People's GenesOne in 17 Mediterranean men may be descended from ancient Phoenicians.Pesticides, Fertilizers Linked to Frog DeclineA pesticide is found to promote parasites among amphibians.Hubble Telescope Taking Photos AgainThe Hubble Space Telescope is once again snapping stunning photos of the universe.Andean Mummy Hairs Show Hallucinogen UseScientists find direct evidence of hallucinogenic drug use among ancient Andeans.Opals on Mars Reveal Planet's Long Wet PastOpals found on Mars suggest the planet has been wet for much longer. |
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