Related by context. Frequent words. (Click for all words.) 68 stalagmites 66 lava tubes 65 igneous rocks 63 stalactite 62 stromatolites 61 snail shells 61 zircons 61 lake sediments 61 stalagmite 60 landforms 60 stalactites 59 rock outcrops 59 igneous rock 59 sandstone formations 59 isotope ratios 58 calcite 58 basaltic 57 mud volcanoes 57 microfossils 57 fossils 57 limestone caves 57 quartz crystals 56 basalts 56 lavas 56 foraminifera 56 salt crystals 56 geological formations 56 marine sediments 56 geologic 56 spinel 56 manganese oxide 56 spherules 56 middens 56 landform 56 calcareous 55 radiocarbon dated 55 sedimentary rock 55 nanosized 55 isotopic composition 55 limestone formations 55 hydrothermal vent 55 olivine 55 iron oxides 55 cinnabar 55 continental crust 55 haloes 55 depositional 54 Lake Vostok 54 Valles Marineris 54 morphologies 54 sediment cores 54 trilobites 54 ammonites 54 pre Incan 54 paleoclimate 54 termite mounds 54 oxygen isotopes 54 lunar soil 54 temperate forests 53 basalt 53 abundances 53 nacre 53 rock formations 53 hydrothermal activity 53 morphologically 53 diatom 53 seamounts 53 placental mammals 52 igneous 52 relict 52 osmium 52 clasts 52 magmas 52 pictographs 52 breccia pipes 52 isotopic 52 striations 52 polar caps 52 Palaeolithic 52 whorls 52 garnets 52 Quaternary 52 elemental composition 51 Harappan 51 mudstone 51 Olympus Mons 51 biogeochemical 51 caves 51 Burgess Shale 51 beryl 51 volcanic peaks 51 geologic formations 51 scarps 51 retreating glaciers 51 coprolites 51 lithosphere 51 hydrothermal vents 51 crystals 51 monazite 51 hieroglyphs 51 spectral signatures