Geology Reference
In-Depth Information
Perhaps more than any other events in Earth's history, these wildly erratic snowball-hot-
house cycles reveal a planet knocked out of kilter. The flip-flopping Neoproterozoic cli-
mate led directly to an unprecedented rise in atmospheric oxygen, a transition that paved
the way for the first animals and plants and the colonization of the continents. With such
biological innovation, evolving Earth soon became infested with novelties—swimming,
burrowing, crawling, and flying creatures boasting ever more extreme habitats and behavi-
ors. Indeed, with the advent of an oxygen-rich atmosphere 650 million years ago, for the
very first time in Earth's long history you the time traveler could have stood on the ancient
alien landscape and breathed deeply without dying in agony. For the first time, you might
have gathered a meager meal of green slime, while avoiding a fatal dose of ultraviolet ra-
diation.
Todayweareonceagainenteringaperiodofdramaticclimatechange,andpositivefeed-
backs appear to be taking hold. Reflective glacial ice is melting at an accelerating rate, ex-
posing more and more ocean and land to absorb more of the Sun's energy. Trees are being
cut and burned, thus pumping more carbon dioxide into the atmosphere while decreasing
the size of the critical CO
2
-consuming forest. And perhaps most critically, the accelerat-
ing release of methane from permafrost and deep ocean ices may raise global temperatures
evenmore,triggeringthereleaseofevenmoremethane,tippingthebalance.IfEarth'spast
holdsanylessonsforourtime,theNeoproterozoic'sstoryofsuddenclimatechangeshould
appear at the top ofthe list. Foreven as its snowball-hothouse shifts opened upnew oppor-
tunities for evolving life, with each episode of climate reversal, almost every living thing
died.
