Even after stripping out the more crackpot notions there are still more theories for what caused the extinction events than there have been events. At least two dozen potential culprits have been identified as causes or prime contributors: global warming, global cooling, changing sea levels, oxygen depletion of the seas (a condition known as anoxia), epidemics, giant leaks of methane gas from the seafloor, meteor and comet impacts, runaway hurricanes of a type known as hypercanes, huge volcanic upwellings, catastrophic solar flares.
即使去掉了不大切合实际的观点以后，解释灭绝事件原因的理论依然多子事件本身。至少有20来只可能的黑手被认为是原因或者主要帮手，包括全球变暖、全球变冷、海平面变化、海洋氧气大幅度减少（所谓的缺氧）、传染病、海床大量甲烷泄漏、陨石和彗星撞击、一种所谓“超强风”的猛烈飓风、强烈的火山喷发，以及灾难性的太阳耀斑。

This last is a particularly intriguing possibility. Nobody knows how big solar flares can get because we have only been watching them since the beginning of the space age, but the Sun is a mighty engine and its storms are commensurately enormous. A typical solar flare — something we wouldn't even notice on Earth — will release the energy equivalent of a billion hydrogen bombs and fling into space a hundred billion tons or so of murderous high-energy particles. The magnetosphere and atmosphere between them normally swat these back into space or steer them safely toward the poles (where they produce the Earth's comely auroras), but it is thought that an unusually big blast, say a hundred times the typical flare, could overwhelm our ethereal defenses. The light show would be a glorious one, but it would almost certainly kill a very high proportion of all that basked in its glow. Moreover, and rather chillingly, according to Bruce Tsurutani of the NASA Jet Propulsion Laboratory, "it would leave no trace in history."
太阳耀斑是一种尤其令人感兴趣的可能性。谁也不知道太阳耀斑会变得多大，因为我们只是从空间时代才开始观测太阳耀斑。但是，太阳是一台大马达，它兴起的风暴是极其巨大的。一次普通的太阳耀斑——我们在地球上甚至还注意不到——释放出相当于10亿颗氢弹的能量，向空间抛出l000亿吨危险的高能粒子。磁层和大气通常一块儿把这些掷回空间，或者把它们安全地引向两极（它们在那里产生地球美丽的极光）。据认为，一次极大的爆发，比如100倍于普通耀斑的耀斑，可以毁坏我们稀薄的防御层。那道光华是很壮丽的，但几乎肯定会使暴露在光里的很大部分生物丧命。而且，令人寒心的是。据美国国家航空和航天局喷气推进实验室的布鲁斯·楚鲁塔尼说：“它在历史上不会留下痕迹。”