aa abyssal rock basalt base basement basic basis bearing wall bed bedding belly block lava bottom bottom side bottommost brash breccia breech buttocks central conglomerate crag deepest downside druid stone essential festooned pahoehoe floor flooring focal fond footing foundation fundament fundamental gneiss granite ground grounds groundwork hardpan igneous rock indispensable infrastructure lava life-and-death life-or-death limestone living rock lower side lower strata lowest lowest layer lowest level lowest point magma mantlerock material metamorphic rock monolith nadir nether side nethermost nethermost level of vital importance pahoehoe pavement pillar pillow lava porphyry principle pudding stone radical regolith riprap rock rock bottom rock-bottom root ropy lava rubble rubblestone rudiment sandstone sarsen schist scoria scree seat sedimentary rock shelly pahoehoe sill solid ground solid rock stereobate stone stylobate substantive substratum substruction substructure talus terra firma tower tufa tuff underbelly underbuilding undercarriage undergirding underlayer underlying level undermost underneath underpinning underside understruction understructure vital