Related by context. Frequent words. (Click for all words.) 56 glaciation 54 Pliocene 54 dinosaurs roamed 53 interglacial 53 isotopic 53 Carboniferous 53 marine sediments 52 Precambrian 52 Quaternary 52 Martian 52 martian 52 Medieval Warm Period 51 epochs 51 volcanism 51 Cretaceous Period 50 microfossils 50 eons 50 Holocene 50 interglacial period 50 Ordovician 50 lavas 50 Late Cretaceous 49 Cretaceous 49 millenniums 49 plate tectonics 49 lake sediments 49 radiocarbon 49 radioactive decay 49 millennia 48 primordial soup 48 stalagmite 48 Pleistocene 48 lithosphere 48 Little Ice Age 48 primeval 48 supernova explosion 47 magmatic 47 ancients 47 Paleolithic 47 mass extinctions 47 Mesozoic 47 Meridiani 47 trilobites 47 continental crust 47 aeons 47 volcanic 47 geologic 47 millenia 47 ancient 46 primordial 46 oceanic crust 46 Eocene 46 prehistoric 46 eruptive 46 Minoan 46 preindustrial 46 sedimentary rock 46 paleo 46 Han Dynasty 45 abundances 45 cosmological 45 earths 45 prehistory 45 biogenic 45 basalts 45 neolithic 45 igneous 45 Silurian 45 sediment cores 45 atmospheric 45 atmospheric CO 45 Rig Veda 45 Bronze Age 45 Incas 45 thermosphere 45 abiotic 44 hydrothermal vents 44 Gliese #g 44 oxygen isotopes 44 Norman Conquest 44 calcite 44 ancient civilization 44 glacial 44 epoch 44 cometary 44 Jurassic 44 Martian landscape 44 Mesoamerican 44 continental drift 44 radiocarbon dating 44 subatomic particle 44 cosmic microwave background 44 permafrost 44 megafauna 44 crustal 43 olivine 43 mass extinction 43 Proterozoic 43 sunspot cycle 43 Archaic 43 tectonic