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
Sigma heat extracted by cooling the water vapor below its condensation point does not count towards sigma heat. The reference temperature is usually , although is sometimes used as well. Assuming a reference temperature of 0°F, the following formula may be used under standard temperature ranges and pressure: formula_2 The equivalent metric formula: formula_6 Sigma heat is not the same as the enthalpy of the humid air above the reference temperature. (Enthalpy is sometimes called "total heat" or "true total heat") Unlike sigma heat, enthalpy does include the energy which would be extracted in cooling the condensed water vapor all the way