Encyclopedia of Global Resources part 26 provides a wide variety of perspectives on both traditional and more recent views of Earth's resources. It serves as a bridge connecting the domains of resource exploitation, environmentalism, geology, and biology, and it explains their interrelationships in terms that students and other nonspecialists can understand. The articles in this set are extremely diverse, with articles covering soil, fisheries, forests, aluminum, the Industrial Revolution, the . Department of the Interior, the hydrologic cycle, glass, and placer mineral deposits. . | 220 Coal Global Resources presence of which would ordinarily cause decay of the plant tissue. Under such near-stagnant conditions plant remains are preserved while the presence of hydrogen sulfide discourages the presence of organisms that feed on dead vegetation. Analog environments under which coal is presently forming are found within the Atchafalaya swamp of coastal Louisiana and the many peat-producing regions of Ireland. A layer of peat in excess of 2 meters in thickness and covering more than 5 000 square kilometers is present in the Dismal Swamp of coastal North Carolina and Virginia. The sapropelic class of coal relatively uncommon in distribution and composed of fossil algae and spores is formed through partial decomposition of organic matter by organisms within oxygen-deficient lakes and ponds. Sapropelic coals are subdivided into boghead algae origin and cannel spore origin deposits. The vegetable origin of coal has been accepted since 1825 and is convincingly evidenced by the identification of more than three thousand freshwater plant species in coal beds of Carboniferous 360 to 286 million years ago age. The common association of root structures and even upright stumps with layers of coal indicates that the parent plant material grew and accumulated in place. Detailed geologic studies of rock sequences that lie immediately above and below coal deposits indicate that most coals were formed in coastal regions affected by long-term sea-level cycles characterized by transgressing advancing and regressing retreating shorelines. Such a sequence of rock deposited during a single advance and retreat of the shoreline termed a cyclothem typically contains nonmarine strata separated from overlying marine strata by a single layer of coal. In sections of the Interior coal province a minimum of fifty cyclothems have been recognized some of which can be traced across thousands of square kilometers. Such repetition in a rock sequence is most advantageous to the .
