Related by context. Frequent words. (Click for all words.) 62 Chicxulub 58 supercontinent 57 mass extinction 57 glaciations 56 Cambrian explosion 56 supervolcano 56 Snowball Earth 56 interglacial period 56 WASP #b 55 Siberian permafrost 55 Jurassic Period 55 glaciation 55 continental crust 55 planet Uranus 54 Cretaceous Period 54 moraines 54 Lake Vostok 54 planetary nebula 53 stalactite 53 marine sediments 53 Younger Dryas 53 basaltic 53 striations 53 Ardipithecus ramidus 52 supernova explosion 52 spherules 52 ejecta 52 microfossils 52 Burgess Shale 52 trilobites 52 atmospheric methane 52 oceanic crust 52 mass extinctions 52 placental mammals 52 isotope ratios 52 volcanism 52 lavas 52 radiocarbon dated 52 retreating glaciers 51 pyroclastic 51 ammonites 51 Antarctic ozone 51 stromatolites 51 Gliese #g 51 solar nebula 51 Quaternary 51 Cabeus crater 51 hydrothermal activity 51 foraminifera 51 isotopic composition 51 snail shells 51 oxygen isotopes 50 meteoroid 50 horned dinosaur 50 igneous rocks 50 Tunguska 50 H. erectus 50 elemental composition 50 planetesimals 50 feathered dinosaurs 50 megafauna 50 Galileo spacecraft 50 Ordovician 50 Titan Saturn 50 Crab Nebula 50 igneous rock 50 lunar soil 50 lithosphere 50 interglacial 50 olivine 50 Valles Marineris 49 Paleocene 49 mud volcanoes 49 Late Cretaceous 49 meteorite 49 colliding galaxies 49 Galaxy Evolution 49 Tibetan Plateau 49 volcanically active 49 Halley comet 49 Archaean 49 icecap 49 planetary nebulae 49 theropod 49 Carboniferous 49 polar vortex 49 glacial retreat 49 RQ# 49 calcite 49 observable universe 49 clasts 49 fossilized remains 49 Haumea 49 Ardipithecus 49 basalts 48 Petermann Glacier 48 Precambrian 48 moonlets 48 heliosheath 48 magmas 48 GRB #