Eastern United States
The Eastern United States referred to as the American East or the East, is the region of the United States lying to the north of the Ohio River and to the east of the Mississippi River. In 2011 the 26 states east of the Mississippi had an estimated population of 179,948,346 or 58.28% of the total U. S. population of 308,745,358. The Southern United States constitutes a large region in the south-eastern and south-central United States enumerated as the following: Kentucky, Virginia, West Virginia, North Carolina, South Carolina, Florida, Mississippi and Louisiana, its unique cultural and historic heritage includes the following aspects: Native Americans early European settlements of English, Scots-Irish and German heritage importation of hundreds of thousands of enslaved Africans growth of a large proportion of African Americans in the population reliance on slave labor legacy of the Confederacy after the American Civil War. These led to "the South" developing distinctive customs, musical styles, varied cuisines, that have profoundly shaped traditional American culture.
Many aspects of the South's culture remain rooted in the American Civil War. In the last few decades, the Southern US has been attracting domestic and international migrants, the American South is among the fastest-growing areas in the United States. New England is a region of the United States located in the northeastern corner of the country, bounded by the Atlantic Ocean and the state of New York, consisting of the modern states of Maine, New Hampshire, Massachusetts, Rhode Island, Connecticut. In one of the earliest English settlements in the New World, English Pilgrims from Europe first settled in New England in 1620, in the colony of Plymouth. In the late 18th century, the New England colonies would be among the first North American British colonies to demonstrate ambitions of independence from the British Crown, although they would threaten secession over the War of 1812 between the United States and Britain. New England produced the first examples of American literature and philosophy and was home to the beginnings of free public education.
In the 19th century, it played a prominent role in the movement to abolish slavery in the United States. It was the first region of the United States to be transformed by the Industrial Revolution. An area in which parts were Republican, it is now a region with one of the highest levels of support for the Democratic Party in the United States, with the majority of voters in every state voting for the Democrats in the 1992, 1996, 2004, 2008, 2012 and 2016 Presidential elections, every state but New Hampshire voting for Al Gore in 2000; the Midwestern United States is one of the four geographic regions within the United States that are recognized by the United States Census Bureau. Seven states in the central and inland northeastern US, traditionally considered to be part of the Midwest, can be classified as being part of the Eastern United States: Illinois, Iowa, Minnesota and Wisconsin. A 2006 Census Bureau estimate put the population at 66,217,736; the United States Census Bureau divides this region into the East North Central States and the West North Central States.
Chicago is the largest city in the region, followed by Columbus. Chicago has the largest metropolitan statistical area, followed by Detroit, Minneapolis – Saint Paul. Sault Ste. Marie, Michigan is the oldest city in the region, having been founded by French missionaries and explorers in 1668; the term Midwest has been in common use for over 100 years. Another term sometimes applied to the same general region is "the heartland". Other designations for the region have fallen into disuse, such as the "Northwest" or "Old Northwest" and "Mid-America". Since the book Middletown appeared in 1929, sociologists have used Midwestern cities as "typical" of the entire nation; the region has a higher employment-to-population ratio than the Northeast, the West, the South, or the Sun Belt states. Four of the states associated with the Midwestern United States are traditionally referred to as belonging in part to the Great Plains region; the following is a list of the 24 largest cities in the East by population: East Coast of the United States Eastern Canada Territories of the United States on stamps
Red beds are sedimentary rocks, which consist of sandstone and shale that are predominantly red in color due to the presence of ferric oxides. These red-colored sedimentary strata locally contain thin beds of conglomerate, limestone, or some combination of these sedimentary rocks; the ferric oxides, which are responsible for the red color of red beds occur as a coating on the grains of sediments comprising red beds. Classic examples of red beds are the Permian and Triassic strata of the western United States and the Devonian Old Red Sandstone facies of Europe. Krynine suggested that the red beds were formed by the erosion and redeposition of red soils or older red beds, but a fundamental problem with this hypothesis is the relative scarcity of red-colored source sediments of suitable age close to an area of red bed sediments in Cheshire, England. Van Houten developed the idea to include the in situ reddening of the sediment by the dehydration of brown or drab colored ferric hydroxides; these ferric hydroxides include goethite and so-called "amorphous ferric hydroxide" or limonite.
Much of this material may be the mineral ferrihydrite. This dehydration or "aging" process has been found to be intimately associated with pedogenesis in alluvial floodplains and desert environments. Berner showed that goethite is unstable relative to hematite and, in the absence of water or at elevated temperature, will dehydrate according to the reaction: 2FeOOH → Fe2O3 +H2OThe Gibbs Free Energy for the reaction goethite → hematite is −2.76kJ/mol and Langmuir showed that G becomes negative with smaller particle size. Thus detrital ferric hydroxides, including goethite and ferrihydrite, will spontaneously transform into red-colored hematite pigment with time; this process not only accounts for the progressive reddening of alluvium but the fact that older desert dune sands are more intensely reddened than their younger equivalents. The formation of red beds during burial diagenesis was described by Walker and Walker et al.. The key to this mechanism is the intrastratal alteration of ferromagnesian silicates by oxygenated groundwaters during burial.
Walker’s studies show that the hydrolysis of hornblende and other iron-bearing detritus follows Goldich dissolution series. This is controlled by the Gibbs free energy of the particular reaction. For example, the most altered material would be olivine: e.g. Fe2SiO4 + O2 → Fe2O3 + SiO2 with E = -27.53kJ/molA key feature of this process, exemplified by the reaction, is the production of a suite of by products which are precipitated as authigenic phases. These include mixed layer clays, potassium feldspar and carbonates as well as the pigmentary ferric oxides. Reddening progresses as the diagenetic alteration becomes more advanced and is thus a time dependent mechanism; the other implication is that reddening of this type is not specific to a particular depositional environment. However, the favourable conditions for diagenetic red bed formation i.e. positive Eh and neutral-alkaline pH are most found in hot, semi-arid areas, this is why red beds are traditionally associated with such climates. Secondary red beds are characterized by irregular color zonation related to sub-unconformity weathering profiles.
The color boundaries may cross-cut lithological contacts and show more intense reddening adjacent to unconformities. Johnson et al. have showed how secondary reddening phases might be superimposed on earlier formed primary red beds in the Carboniferous of the southern North Sea. The general conditions leading to post-diagenetic alteration have been described by Mücke. Important reactions include pyrite oxidation: 3O2 + 4FeS2→ Fe2O3 + 8S E = −789 kJ/moland siderite oxidation: O2 + 4FeCO3 → 2Fe2O3 + 4CO2 E = −346 kJ/molSecondary red beds formed in this way are an excellent example of telodiagenesis, they are linked to the uplift and surface weathering of deposited sediments and require conditions similar to primary and diagenetic red beds for their formation. Red Beds of Texas and Oklahoma Chugwater Formation Red Hills, Kansas Old Red Sandstone New Red Sandstone American Geological Institute, Dictionary of Geological Terms, p. 416. Berner R. A. 1969. Goethite stability and origin of red beds. Geochimica Cosmomochimica Acta, 35, pp 267-273.
Krynine, P. D. 1950, Petrology and origin of the Triassic sedimentary Bulletin of the Connecticut Geology and Natural History Survey, 73, 239p. Langmuir, D. 1971, Particle size effect on the reaction Goethite = Hematite + Water. American Journal of Science, 271, pp 147-156. Mücke, A. 1994. Part 1. Postdiagenetic ferruginization of sedimentary rocks - including a comparative study of the reddening of red beds. Wolf, K. H. and Chilingarian, G V. pp 361-395 Diagenesis, IV. Developments in Sedimentology 5 1, Amsterdam. Van Houten, F. B. 1973, Origin of red beds. A review -1961-1972. Annual Review Earth Planetary Science, 1, pp 39-61 Walker, T. R. 1967, Formation of red beds in modern and ancient deserts. Bulletin of the Geological Society of America, 78, pp 353-368. Pictures of Permo-Triassic red beds in Palo Duro Canyon
Mudrocks are a class of fine grained siliciclastic sedimentary rocks. The varying types of mudrocks include: siltstone, mudstone and shale. Most of the particles of which the stone is composed are less than 0.0625 mm and are too small to study in the field. At first sight the rock types look quite similar. There has been a great deal of disagreement involving the classification of mudrocks. There are a few important hurdles to classification, including: Mudrocks are the least understood, one of the most understudied sedimentary rocks to date It is difficult to study mudrock constituents, due to their diminutive size and susceptibility to weathering on outcrops And most there is more than one classification scheme accepted by scientistsMudrocks make up fifty percent of the sedimentary rocks in the geologic record, are the most widespread deposits on Earth. Fine sediment is the most abundant product of erosion, these sediments contribute to the overall omnipresence of mudrocks. With increased pressure over time the platey clay minerals may become aligned, with the appearance of parallel layering.
This finely bedded material that splits into thin layers is called shale, as distinct from mudstone. The lack of fissility or layering in mudstone may be due either to the original texture or to the disruption of layering by burrowing organisms in the sediment prior to lithification. From the beginning of civilization, when pottery and mudbricks were made by hand, to now, mudrocks have been important; the first book on mudrocks, Geologie des Argils by Millot, was not published until 1964. Literature on this omnipresent rock-type has been increasing in recent years, technology continues to allow for better analysis. Mudrocks, by definition, consist of at least fifty percent mud-sized particles. Mud is composed of silt-sized particles that are between 1/16 – 1/256 of a millimeter in diameter, clay-sized particles which are less than 1/256 millimeter. Mudrocks contain clay minerals, quartz and feldspars, they can contain the following particles at less than 63 micrometres: calcite, siderite, marcasite, heavy minerals, organic carbon.
There are various synonyms for fine-grained siliciclastic rocks containing fifty percent or more of its constituents less than 1/256 of a millimeter. Mudstones, shales and argillites are common qualifiers, or umbrella-terms; the term "mudrock" allows for further subdivisions of siltstone, claystone and shale. For example, a siltstone would be made of more than 50-percent grains that equate to 1/16 - 1/256 of a millimeter. "Shale" denotes fissility, which implies an ability to part or break parallel to stratification. Siltstone and claystone implies lithified, or hardened, detritus without fissility. Overall, "mudrocks" may be the most useful qualifying term, because it allows for rocks to be divided by its greatest portion of contributing grains and their respective grain size, whether silt, clay, or mud. A claystone is lithified, non-fissile mudrock. In order for a rock to be considered a claystone, it must consist of up to fifty percent clay, which measures less than 1/256 of a millimeter in particle size.
Clay minerals are integral to mudrocks, represent the first or second most abundant constituent by volume. There are 35 recognized clay mineral species on Earth, they able to flow. Clay is by far the smallest particles recognized in mudrocks. Most materials in nature are clay minerals, but quartz, iron oxides, carbonates can weather to sizes of a typical clay mineral. For a size comparison, a clay-sized particle is 1/1000 the size of a sand grain; this means a clay particle will travel 1000 times further at constant water velocity, thus requiring quieter conditions for settlement. The formation of clay is well understood, can come from soil, volcanic ash, glaciation. Ancient mudrocks are another source, because they disintegrate easily. Feldspar, amphiboles and volcanic glass are the principle donors of clay minerals. A mudstone is a siliciclastic sedimentary rock that contains a mixture of silt- and clay-sized particles; the terminology of "mudstone" is not to be confused with the Dunham classification scheme for limestones.
In Dunham's classification, a mudstone is any limestone containing less than ten percent carbonate grains. Note, a siliciclastic mudstone does not deal with carbonate grains. Friedman and Kopaska-Merkel suggest the use of "lime mudstone" to avoid confusion with siliciclastic rocks. A siltstone is a non-fissile mudrock. In order for a rock to be named a siltstone, it must contain over fifty percent silt-sized material. Silt is any particle smaller than sand, 1/16 of a millimeter, larger than clay, 1/256 of millimeter. Silt is believed to be the product of physical weathering, which can involve freezing and thawing, thermal expansion, release of pressure. Physical weathering does not involve any chemical changes in the rock, it may be best summarised as the physical breaking apart of a rock. One of the highest proportions of silt found on Earth is in the Himalayas, where phyllites are exposed to rainfall of up to five to ten meters a year. Quartz and feldspar are the biggest contributors to the silt realm
The Allegheny River is a 325-mile long headwater stream of the Ohio River in western Pennsylvania and New York, United States. The Allegheny River runs from its headwaters just below the middle of Pennsylvania's northern border northwesterly into New York in a zigzag southwesterly across the border and through Western Pennsylvania to join the Monongahela River at the Forks of the Ohio on the "Point" of Point State Park in Downtown Pittsburgh, Pennsylvania; the Allegheny River is, by volume, the main headstream of both the Mississippi Rivers. The Allegheny was considered to be the upper Ohio River by both Native Americans and European settlers; the shallow river has been made navigable upstream from Pittsburgh to East Brady by a series of locks and dams constructed in the early 20th century. A 24-mile long portion of the upper river in Warren and McKean counties of Pennsylvania and Cattaraugus County in New York is the Allegheny Reservoir known as Lake Kinzua, created by the erection of the Kinzua Dam in 1965 for flood control.
The name of the river comes from one of a number of Delaware Indian phrases which are homophones of the English name, with varying translations. The name Allegheny comes from Lenape welhik hane or oolikhanna, which means'best flowing river of the hills' or'beautiful stream'. There is a Lenape legend of a tribe called "Allegewi"; the following account of the origin of the name Allegheny was given in 1780 by Moravian missionary David Zeisberger: "All this land and region, stretching as far as the creeks and waters that flow into the Alleghene the Delawares called Alligewinenk, which means'a land into which they came from distant parts'. The river itself, however, is called Alligewi Sipo; the whites have made Alleghene out of this, the Six Nations calling the river the Ohio."Indians, including the Lenni Lenape and Iroquois, considered the Allegheny and Ohio rivers as the same, as is suggested by a New York State road sign on Interstate 86 that refers to the Allegheny River as Ohiːyo'. The Geographic Names Information System lists O-hi-o as variant names.
The river is called Ohi:'i:o` in the Seneca language. In New York, areas around the river are named with the alternate spelling Allegany in reference to the river. Port Allegany, located along the river in Pennsylvania near the border with New York follows this pattern; the Allegheny River rises in north central Pennsylvania, on Cobb Hill in Alleghany Township in north central Potter County, 8 miles south of the New York border and a few miles northwest of the eastern triple divide. The stream flows south and passes under Pennsylvania Route 49 11 miles northeast of Coudersport where a historical marker that declares the start of the river is located. Cobb Hill is about a mile north; the stream flows southwest paralleling Route 49 to Coudersport. It continues west to Port Allegany turns north into western New York, looping westward across southern Cattaraugus County for 30 miles, past Portville, Olean and Salamanca and flowing through Seneca Indian Nation lands close to the northern boundary of Allegany State Park before re-entering northwestern Pennsylvania within the Allegheny Reservoir just east of the Warren-McKean county line, approx.
10 miles northeast of Warren. It flows in a broad zigzag course southwest across Western Pennsylvania. South of Franklin it turns southeast across Clarion County in a meandering course turns again southwest across Armstrong County, flowing past Kittanning, Ford City and Freeport; the river enters both Allegheny and Westmoreland counties, the Pittsburgh suburbs, the City of Pittsburgh from the northeast. It passes the North Side, downtown Pittsburgh, Point State Park; the Allegheny joins with the Monongahela River at the "Point" in downtown Pittsburgh to form the Ohio River. The river is 325 miles long, running through the U. S. states of New Pennsylvania. It drains a rural dissected plateau of 11,580 square miles in the northern Allegheny Plateau, providing the northeastern most drainage in the watershed of the Mississippi River, its tributaries reach to within 8 miles of Lake Erie in southwestern New York. Water from the Allegheny River flows into the Gulf of Mexico via the Ohio and Mississippi rivers.
The Allegheny Valley has been one of the most productive areas of fossil fuel extraction in United States history, with its extensive deposits of coal and natural gas. In its upper reaches, the Allegheny River is joined from the south by Potato Creek 1.7 miles downstream of Coryville and from the north by Olean Creek at Olean, New York. Tunungwant "Tuna" Creek joins the river from the south in New York. After re-entering Pennsylvania, the river is joined from the east by Kinzua Creek 10 miles upstream of Warren.
The Permian is a geologic period and system which spans 47 million years from the end of the Carboniferous Period 298.9 million years ago, to the beginning of the Triassic period 251.902 Mya. It is the last period of the Paleozoic era; the concept of the Permian was introduced in 1841 by geologist Sir Roderick Murchison, who named it after the city of Perm. The Permian witnessed the diversification of the early amniotes into the ancestral groups of the mammals, turtles and archosaurs; the world at the time was dominated by two continents known as Pangaea and Siberia, surrounded by a global ocean called Panthalassa. The Carboniferous rainforest collapse left behind vast regions of desert within the continental interior. Amniotes, who could better cope with these drier conditions, rose to dominance in place of their amphibian ancestors; the Permian ended with the Permian–Triassic extinction event, the largest mass extinction in Earth's history, in which nearly 96% of marine species and 70% of terrestrial species died out.
It would take well into the Triassic for life to recover from this catastrophe. Recovery from the Permian–Triassic extinction event was protracted; the term "Permian" was introduced into geology in 1841 by Sir R. I. Murchison, president of the Geological Society of London, who identified typical strata in extensive Russian explorations undertaken with Édouard de Verneuil; the region now lies in the Perm Krai of Russia. Official ICS 2017 subdivisions of the Permian System from most recent to most ancient rock layers are: Lopingian epoch Changhsingian Wuchiapingian Others: Waiitian Makabewan Ochoan Guadalupian epoch Capitanian stage Wordian stage Roadian stage Others: Kazanian or Maokovian Braxtonian stage Cisuralian epoch Kungurian stage Artinskian stage Sakmarian stage Asselian stage Others: Telfordian Mangapirian Sea levels in the Permian remained low, near-shore environments were reduced as all major landmasses collected into a single continent—Pangaea; this could have in part caused the widespread extinctions of marine species at the end of the period by reducing shallow coastal areas preferred by many marine organisms.
During the Permian, all the Earth's major landmasses were collected into a single supercontinent known as Pangaea. Pangaea straddled the equator and extended toward the poles, with a corresponding effect on ocean currents in the single great ocean, the Paleo-Tethys Ocean, a large ocean that existed between Asia and Gondwana; the Cimmeria continent rifted away from Gondwana and drifted north to Laurasia, causing the Paleo-Tethys Ocean to shrink. A new ocean was growing on its southern end, the Tethys Ocean, an ocean that would dominate much of the Mesozoic era. Large continental landmass interiors experience climates with extreme variations of heat and cold and monsoon conditions with seasonal rainfall patterns. Deserts seem to have been widespread on Pangaea; such dry conditions favored gymnosperms, plants with seeds enclosed in a protective cover, over plants such as ferns that disperse spores in a wetter environment. The first modern trees appeared in the Permian. Three general areas are noted for their extensive Permian deposits—the Ural Mountains and the southwest of North America, including the Texas red beds.
The Permian Basin in the U. S. states of Texas and New Mexico is so named because it has one of the thickest deposits of Permian rocks in the world. The climate in the Permian was quite varied. At the start of the Permian, the Earth was still in an ice age. Glaciers receded around the mid-Permian period as the climate warmed, drying the continent's interiors. In the late Permian period, the drying continued although the temperature cycled between warm and cool cycles. Permian marine deposits are rich in fossil mollusks and brachiopods. Fossilized shells of two kinds of invertebrates are used to identify Permian strata and correlate them between sites: fusulinids, a kind of shelled amoeba-like protist, one of the foraminiferans, ammonoids, shelled cephalopods that are distant relatives of the modern nautilus. By the close of the Permian, trilobites and a host of other marine groups became extinct. Terrestrial life in the Permian included diverse plants, fungi and various types of tetrapods; the period saw a massive desert covering the interior of Pangaea.
The warm zone spread in the northern hemisphere. The rocks formed at that time were stained red by iron oxides, the result of intense heating by the sun of a surface devoid of vegetation cover. A number of older types of plants and animals became marginal elements; the Permian began with the Carboniferous flora still flourishing. About the middle of the Permian a major transition in vegetation began; the swamp-loving
Lithostratigraphy is a sub-discipline of stratigraphy, the geological science associated with the study of strata or rock layers. Major focuses include geochronology, comparative geology, petrology. In general a stratum will be igneous or sedimentary relating to how the rock was formed. Sedimentary layers are laid down by deposition of sediment associated with weathering processes, decaying organic matters or through chemical precipitation; these layers are distinguishable as having many fossils and are important for the study of biostratigraphy. Igneous layers are either plutonic or volcanic in character depending upon the cooling rate of the rock; these layers are devoid of fossils and represent intrusions and volcanic activity that occurred over the geologic history of the area. There are a number of principles; when an igneous rock cuts across a formation of sedimentary rock we can say that the igneous intrusion is younger than the sedimentary rock. The principle of superposition states that a sedimentary rock layer in a tectonically undisturbed stratum is younger than the one beneath and older than the one above it.
The principle of original horizontality states that the deposition of sediments occurs as horizontal beds. A lithostratigraphic unit conforms to the law of superposition, which state that in any succession of strata, not disturbed or overturned since deposition, younger rocks lies above older rocks; the principle of lateral continuity states that a set of bed extends and can be traceable over a large area. Lithostratigraphic units are defined on the basis of observable rock characteristics; the descriptions of strata based on physical appearance define facies. Lithostratigraphic units are only defined by lithic characteristics, not by age. Stratotype: A designated type of unit consisting of accessible rocks that contain clear-cut characteristics which are representative of a particular lithostratigraphic unit. Lithosome: Masses of rock of uniform character and having interchanging relationships with adjacent masses of different lithology. E.g.: shale lithosome, limestone lithosome. The fundamental Lithostratigraphic unit is the formation.
A formation is a lithologically distinctive stratigraphic unit, large enough to be mappable and traceable. Formations may be subdivided into members and beds and aggregated with other formations into groups and supergroups. Two types of contact: conformable and unconformable. Conformable: unbroken deposition, no break or hiatus; the surface strata resulting is called a conformity. Two types of contact between conformable strata: abrupt contacts and gradational contact. Unconformable: period of erosion/non-deposition; the surface stratum resulting is called an unconformity. Four types of unconformity: Angular unconformity: younger sediment lies upon an eroded surface of tilted or folded older rocks; the older rock dips at a different angle from the younger. Disconformity: the contact between younger and older beds is marked by visible, irregular erosional surfaces. Paleosol might develop right above the disconformity surface because of the non-deposition setting. Paraconformity: the bedding planes below and above the unconformity are parallel.
A time gap is present, as shown by a faunal break, but there is no erosion, just a period of non-deposition. Nonconformity: young sediments are deposited right above older igneous or metamorphic rocks. To correlate lithostratigraphic units, geologists define facies, look for key beds or key sequences that can be used as a datum. Direct correlation: based on lithology, structure, thickness… Indirect correlation: electric log correlation Biostratigraphy Chronostratigraphy Topostratigraphy Online stratigraphic column generator Tamu.edu: Lithostratigraphy USGS.gov: Lithostratigraphy Agenames
An unconformity is a buried erosional or non-depositional surface separating two rock masses or strata of different ages, indicating that sediment deposition was not continuous. In general, the older layer was exposed to erosion for an interval of time before deposition of the younger, but the term is used to describe any break in the sedimentary geologic record; the significance of angular unconformity was shown by James Hutton, who found examples of Hutton's Unconformity at Jedburgh in 1787 and at Siccar Point in 1788. The rocks above an unconformity are younger than the rocks beneath. An unconformity represents time; the local record for that time interval is missing and geologists must use other clues to discover that part of the geologic history of that area. The interval of geologic time not represented is called a hiatus. A disconformity is an unconformity between parallel layers of sedimentary rocks which represents a period of erosion or non-deposition. Disconformities are marked by features of subaerial erosion.
This type of erosion can leave paleosols in the rock record. A paraconformity is a type of disconformity in which the separation is a simple bedding plane with no obvious buried erosional surface. A nonconformity exists between sedimentary rocks and metamorphic or igneous rocks when the sedimentary rock lies above and was deposited on the pre-existing and eroded metamorphic or igneous rock. Namely, if the rock below the break is igneous or has lost its bedding due to metamorphism, the plane of juncture is a nonconformity. An angular unconformity is an unconformity where horizontally parallel strata of sedimentary rock are deposited on tilted and eroded layers, producing an angular discordance with the overlying horizontal layers; the whole sequence may be deformed and tilted by further orogenic activity. A typical case history is presented by the paleotectonic evolution of the Briançonnais realm during the Jurassic. A paraconformity is a type of unconformity, it is called nondepositional unconformity or pseudoconformity.
Short paraconformities are called diastems. A buttress unconformity occurs when younger bedding is deposited against older strata thus influencing its bedding structure. A blended unconformity is a type of disconformity or nonconformity with no distinct separation plane or contact, sometimes consisting of soils, paleosols, or beds of pebbles derived from the underlying rock. U. S. Bureau of Mines Dictionary of Mining and Related Terms published on CD-ROM in 1996