Related by context. Frequent words. (Click for all words.) 60 mass extinctions 57 volcanism 57 anoxic 57 glaciation 56 mass extinction 55 supernova explosion 54 Ordovician 54 Precambrian 53 Little Ice Age 52 Late Cretaceous 52 Pliocene 51 diatoms 51 magmatic 51 eukaryotes 51 plate tectonics 50 archaea 50 CO2 concentrations 49 atmospheric CO2 49 Holocene 49 megafauna 49 Pleistocene 49 single celled organisms 49 single celled 49 atmospheric carbon dioxide 49 cyanobacteria 48 greenhouse warming 48 atmospheric concentrations 48 olivine 48 Proterozoic 48 supernova explosions 47 abundances 47 mid latitudes 47 phytoplankton 47 sedimentary rock 46 extinctions 46 perturbation 46 sunspot activity 46 sediments 46 oxygen depletion 46 isotopic 46 speciation 46 Eocene 46 peridotite 46 gamma ray burst 46 Cretaceous 46 subduction zones 46 dwarf galaxy 46 hypoxia 46 superoxide 46 radioactive decay 46 supernovae 46 crustal 46 Medieval Warm Period 46 scientists theorize 46 Triassic 46 tetrapods 45 methane 45 Nature Geoscience 45 biodegradation 45 nucleation 45 hydrothermal 45 adsorbed 45 Homo sapiens 45 Eta Carinae 45 epochs 45 GRBs 45 rocky planets 45 ejecta 45 atmospheric circulation 45 cosmic microwave background 45 upwelling 45 neutrino 45 quasar 44 geologic 44 Paleozoic 44 Martian atmosphere 44 acidification 44 sulfides 44 supernova 44 Saturn rings 44 hydrothermal vents 44 neutron star 44 PETM 44 organic molecules 44 gigatons 44 glacial melt 43 Mesozoic 43 greenhouse gas concentrations 43 seismicity 43 chemical reactions 43 eutrophication 43 Carbon dioxide 43 tectonic 43 Earth crust 43 Australopithecus 43 calcite 43 HD #b [002] 43 vertebrate 43 cometary 43 super Earths 43 volcanic earthquakes