Related by context. Frequent words. (Click for all words.) 44 paleontological 44 lava tubes 43 karst 43 pocket gophers 43 Chihuahuan Desert 43 fossils 42 insects spiders 42 caves 42 burrows 42 cenotes 42 dinosaur fossils 42 dinosaur fossil 42 Baskfield 41 underground burrows 41 polar craters 41 permafrost 41 Willerslev 41 prehistoric 40 ichthyosaur 40 Migrating birds 40 paleontologists 40 Dunbar Cave 40 subterranean 40 burrow 40 limestone cave 40 Namib Desert 40 archeologists 40 salamanders 39 fossilized bones 39 White Nose Syndrome 39 critters 39 Wallowa Mountains 39 geologic formations 39 cenote 39 Voles 39 subglacial 39 hydrothermal vent 39 underground passageways 39 Seracini 39 archaeologists 38 melting snows 38 alpine tundra 38 cavelike 38 Gila Wilderness 38 rock outcrops 38 mud volcanoes 38 saber toothed tigers 38 Lake Vostok 38 limestone caves 38 Hawass 38 Alemseged 38 dinosaur bones 38 trilobite 38 Lop Nur 38 cave explorers 38 cave 38 Ötzi 38 mineshafts 38 kiva 38 critter 38 termite mounds 38 Rattlesnake Mountain 38 creatures 38 Chaco Canyon 38 Missing hiker 38 dense brush 38 echidnas 38 underwater volcanoes 38 refugia 37 archaeological 37 ancient pyramids 37 basalt rock 37 palaeontologists 37 stalagmites 37 undersea volcanoes 37 receding glaciers 37 mammals 37 nocturnal animals 37 archeological 37 INAH 37 plankton blooms 37 geological formations 37 Sierra Madre mountains 37 coquina 37 grassy plains 37 undersea 37 dinos 37 African savanna 37 pottery fragments 37 extinct volcanoes 37 migrating songbirds 36 Carlsbad Caverns 36 Luray Caverns 36 Barn owls 36 salt licks 36 amphipods 36 middens 36 larvae hatch 36 bears mountain lions 36 sandstone formations 36 Israel Antiquities Authority