Related by context. Frequent words. (Click for all words.) 67 extinctions 58 dinosaurs 55 Little Ice Age 53 atmospheric carbon dioxide 51 Ice Age 51 Homo sapiens 51 extinction 50 mammoths 50 ocean acidification 49 volcanic eruptions 49 plate tectonics 49 Extinction 49 Cretaceous 48 mammals 48 cataclysmic 48 hominids 47 climatic 47 biosphere 47 planet 47 anthropogenic 46 hominid 46 T. rex 46 Greenland ice 46 global warming 46 vertebrates 46 fossil 45 Triassic 45 hydrothermal 45 supernovae 45 supernova 45 evolutionary 45 climate change 44 glaciers 44 fossils 44 Global warming 44 solar flares 44 Neanderthals 44 vertebrate 44 species 44 acidification 44 cyanobacteria 43 coral reefs 43 planetary 43 oceans 43 Earth 43 Industrial Revolution 43 herbivores 43 exoplanets 43 Homo erectus 43 asteroid 43 sunspot 43 volcanic activity 42 warming 42 ecosystems 42 marine ecosystems 42 gamma ray bursts 42 exoplanet 42 Earths 42 prehistoric 42 volcanic eruption 42 mammal 42 cataclysm 42 Big Bang 42 planets 41 Antarctic ice 41 corals 41 Global Warming 41 volcanoes 41 extinct 41 geologic 41 catastrophe 41 amphibians 41 evolutionists 41 upwelling 41 permafrost 41 Antarctic Peninsula 40 famines 40 common ancestor 40 Earth crust 40 tectonic 40 pandemics 40 neutron star 40 phytoplankton 40 polar ice 40 ozone depletion 40 eruption 40 galaxies 40 organisms 40 humans 40 desertification 39 asteroids 39 plankton 39 evolution 39 comets 39 lava flows 39 deforestation 39 dinosaur 39 carbon dioxide 39 polar regions 39 lineages 39 comet