Related by context. Frequent words. (Click for all words.) 54 Arctic permafrost 52 methane hydrates 51 permafrost 49 methane hydrate 48 Lake Vostok 48 icecaps 48 steam vents 48 polar caps 47 volcanic vents 45 gas hydrates 45 subarctic 45 moon Europa 45 tundra 45 Cabeus crater 44 Melting glaciers 44 Polar Regions 44 marine sediments 44 mud volcanoes 43 taiga 43 Snowball Earth 43 seabeds 43 retreating glaciers 43 molten lava 43 polar 43 intertidal zone 43 Arctic Ocean 43 lunar soil 43 hydrothermal vent 43 icecap 43 arctic 43 glaciers 43 melting permafrost 43 Seed Vault 42 Arctic 42 geologic formations 42 Permafrost 42 Saturn moon Enceladus 42 lava tubes 42 woolly mammoths 42 hydrothermal vents 42 thawing permafrost 42 polar ice 42 hydrothermal activity 41 hot springs 41 Antarctic 41 atmospheric methane 41 Microorganisms 41 lunar poles 41 extremophiles 41 Migrating birds 41 temperate forests 41 Qinghai Tibet Plateau 41 salt crystals 41 equatorial regions 41 cryosphere 41 polar regions 41 deplete oxygen 41 methane 41 marine reptiles 41 pikas 40 poleward 40 -# degrees Fahrenheit [002] 40 Arctic seabed 40 magmas 40 lichen 40 narwhals 40 Meridiani 40 melting glacier 40 icy crust 40 geological formations 40 Emperor penguins 40 undersea plumes 40 Cabeus 40 upwellings 40 Saturn moon 40 floes 39 Oort Cloud 39 Spitsbergen 39 polar bears 39 lowland forests 39 sedimentary rock 39 oceans 39 degrees Fahrenheit 39 foraminifera 39 Arctic tundra 39 volcanoes 39 volcanic rock 39 Greenland glaciers 39 glacial melting 39 river deltas 39 subterranean 39 glacial 39 stalagmites 39 Sediments 39 regolith 39 Arctic Circle 39 Tibetan Plateau 39 inhospitable 38 seamounts 38 melting polar 38 Weddell Sea