Related by context. Frequent words. (Click for all words.) 62 hardpan 61 sedimentary rock 60 stalactite 60 calcareous 59 streambed 59 igneous rock 58 lava tube 58 limestone 58 alluvium 58 graben 58 clasts 57 mudstone 57 roadbed 57 coarse sand 57 sandstone 57 basalt 57 calcite 56 geologic formation 56 sinkholes 56 sediment 56 marl 56 talus 56 friable 56 Sinkholes 56 limestones 56 rock outcrops 56 compacted soil 55 bridge abutments 55 lava tubes 55 magma chamber 55 rock formations 55 silty 55 sandy soil 54 decomposed granite 54 roadbeds 54 salt crystals 54 streambeds 54 caliche 54 calcrete 54 peridotite 54 spalling 54 oceanic crust 54 icy crust 54 sediments 54 clay soils 53 siltstone 53 pebbly 53 oxide layer 53 limestone formations 53 sandy loam 53 lakebed 53 marine sediments 53 volcanic rock 53 sandy soils 53 beaver pond 53 geologic formations 53 carbonic acid 53 andesite 53 earth crust 53 crushed limestone 52 silts 52 pyritic 52 siltstones 52 steam vents 52 jasperoid 52 chlorides 52 hydrothermally altered 52 seepage 52 dolomite 52 stromatolites 52 igneous rocks 52 glacial till 52 silt 52 creekbed 52 soils 51 subgrade 51 escarpments 51 breccia zones 51 crust 51 Sediments 51 creek bed 51 lithosphere 51 underground aquifer 51 Upper Cretaceous 51 earthen walls 51 limestone caves 51 coal seams 51 hydrothermal breccia 51 tuffs 51 biotite 51 cenotes 51 continental crust 51 gravels 50 stalagmite 50 karst 50 quartz veinlets 50 intermittent streams 50 nonporous 50 iron oxides 50 wooden pilings 50 basalts