Rock (geology) arkoses (12%). Sedimentary rocks often contain fossils. Sedimentary rocks form under the influence of gravity and typically are deposited in horizontal or near horizontal layers or strata and may be referred to as stratified rocks. A small fraction of sedimentary rocks deposited on steep slopes will show cross bedding where one layer stops abruptly along an interface where another layer eroded the first as it was laid atop the first. Metamorphic rocks are formed by subjecting any rock type—sedimentary rock, igneous rock or another older metamorphic rock—to different temperature and pressure conditions than those in which the original rock was
Ground heat exchanger Ground heat exchanger Ground heat exchangers (GHEs), which are also called geothermal heat exchangers, have emerged as a promising and globally accepted way of exploiting shallow geothermal energy, for example ground-coupled heat pumps, ground heat storage. A GHE is essentially a pipe (e.g., U-, W-, or helical-shaped) in a vertical borehole or a foundation pile of a building, in which a circulating heat-carrying fluid absorbs (or discharges) heat from (or to) the ground. GHEs can have various configurations. This article discusses two kinds of closed loop GHEs, i.e., borehole and foundation pile GHEs. The borehole type is the most common.