Related by context. Frequent words. (Click for all words.) 67 sandstone formations 66 mudstone 62 igneous rock 60 graben 59 sandstone 59 lava tubes 59 tuffs 59 calcareous 58 clasts 58 limestone formations 58 Upper Cretaceous 58 sedimentary rock 58 sandstone cliffs 57 depositional 57 interbedded 57 siltstone 57 calcite 57 batholith 57 talus 56 escarpments 56 basalt 56 stalactite 56 siliceous 56 buttes 56 hydrothermal breccia 56 stratiform 56 granite boulders 56 aragonite 55 siltstones 55 striated 55 landforms 55 alluvium 55 breccia zones 55 dacite 55 Paleocene 55 pyroxenite 55 caldera 55 limestones 55 towering cliffs 55 basaltic 54 silty 54 stalagmite 54 stippled 54 limestone cave 54 rock outcrops 54 quartz monzonite 54 hydrothermally altered 54 Valles Marineris 54 glacial till 54 geologic formation 54 grassy plains 54 NE trending 54 gneiss 54 igneous rocks 54 breccia pipe 54 continental crust 54 hardened lava 54 stratabound 53 Mineralization occurs 53 intertidal 53 outcroppings 53 breccia pipes 53 stratigraphically 53 calcrete 53 schists 53 syncline 53 glaciated 53 stromatolites 53 breccia zone 53 jasperoid 53 steam vents 52 Uranium mineralization 52 overlies 52 graphitic 52 rock formations 52 Olympus Mons 52 felsic volcanic 52 chalcocite 52 oceanic crust 52 sedimentary rocks 52 bornite 52 weakly mineralized 52 lava flows 52 quartz veinlets 52 striations 52 greenish brown 52 outcrops 52 hydrothermal activity 52 magma chamber 52 pyritic 52 basalts 52 haematite 52 biotite 52 brecciated 52 ultramafic rocks 51 Paleozoic 51 salt crystals 51 porphyry mineralization 51 ridges 51 pebbly 51 argillite