Mesa is the American English term for tableland, an elevated area of land with a flat top and sides that are usually steep cliffs. It takes its name from its characteristic table-top shape and it may be called a table hill, table-topped hill or table mountain. It is larger than a butte, which it resembles closely. Examples are found in other nations including Spain, Sardinia and South Africa, India. Grand Mesa is a mesa located in western Colorado in the Southwest United States. Cerro Negro is a mesa in Argentina, the term mesa is used throughout the United States to describe a flat-topped mountain or hill. Mesas form by weathering and erosion of layered rocks that have been uplifted by tectonic activity. This process is called differential erosion, the most resistant rock types include sandstone, quartzite, chert, lava flows and sills. Lava flows and sills, in particular, are resistant to weathering and erosion. The less resistant rock layers are made up of shale. The differences in strength of rock layers is what gives mesas their distinctive shape.
Less resistant rocks are eroded away on the surface into valleys, a large area of very resistant rock, such as a sill may shield the layers below it from erosion while the softer rock surrounding it is eroded into valleys, thus forming a caprock. Differences in rock type reflect on the sides of a mesa, as instead of smooth slopes, the more resistant layers form the cliffs, or stairsteps, while the less resistant layers form gentle slopes, or benches, between the cliffs. Cliffs retreat and are cut off from the main cliff, or plateau. When the cliff edge does not retreat uniformly, but instead is indented by headward eroding streams, as the underlying shale erodes away, it can no longer support the overlying cliff layers, which collapse and retreat. When the caprock has caved away to the point where only a little remains, a transitional zone on Mars, known as the fretted terrain, lies between highly cratered highlands and less cratered lowlands. The younger lowland exhibits steep walled mesas and knobs, the mesa and knobs are separated by flat lying lowlands.
They are thought to form from ice-facilitated mass wasting processes from ground or atmospheric sources, the mesas and knobs decrease in size with increasing distance from the highland escarpment
Dolostone or dolomite rock is a sedimentary carbonate rock that contains a high percentage of the mineral dolomite, CaMg2. In old USGS publications it was referred to as magnesian limestone, dolostone has a stoichiometric ratio of nearly equal amounts of magnesium and calcium. Most dolostones formed as a replacement of limestone or lime mud prior to lithification. It is resistant to erosion and can either contain bedded layers or be unbedded and it is less soluble than limestone in weakly acidic groundwater, but it can still develop solution features over time. Dolostone can act as an oil and natural gas reservoir, the term dolostone was introduced to avoid confusion with the mineral dolomite. The usage of the term dolostone is controversial because the name dolomite was first applied to the rock during the late 18th century, the use of the term dolostone is not recommended by the Glossary of Geology published by the American Geological Institute. It is, used in some geological publications, the geological process of conversion of calcite to dolomite is known as dolomitization and any intermediate product is known as dolomitic limestone.
The dolomite problem refers to the vast worldwide depositions of dolostone in past geologic record eluding a unified explanation for their formation, as with limestone caves, natural caves and solution tubes can form in dolomite rock as a result of dissolution by weak carbonic acid. Calcium carbonate speleothems in the forms of stalactites, flowstone etc, “Dolomite is a common rock type, but a relatively uncommon mineral in speleothems”. Both calcium and magnesium go into solution when dolomite rock is dissolved, the speleothem precipitation sequence is, calcite, Mg-calcite, aragonite and hydromagnesite. Hence, the most common speleothem in caves within dolomite rock karst, is calcium carbonate in the most stable form of calcite. Speleothem types known to have a dolomite constituent include, crusts, flowstone, powder and rafts. Although there are reports of dolomite speleothems known to exist in a number of cave around the world, they are usually in small quantities. Blatt, Tracy, Robert J. Petrology, Sedimentary, tucker, M. E. V. P.
Wright. Zenger, D. H. Mazzullo, S. J. Dolomitization
The petroleum industry includes the global processes of exploration, refining and marketing of petroleum products. The largest volume products of the industry are fuel oil and gasoline, Petroleum is the raw material for many chemical products, including pharmaceuticals, fertilizers, synthetic fragrances, and plastics. The industry is divided into three major components, upstream and downstream. Midstream operations are included in the downstream category. Petroleum is vital to many industries, and is of importance to the maintenance of industrial civilization in its current configuration, and thus is a critical concern for many nations. Oil accounts for a percentage of the world’s energy consumption, ranging from a low of 32% for Europe and Asia. Other geographic regions consumption patterns are as follows and Central America, the world consumes 30 billion barrels of oil per year, with developed nations being the largest consumers. The United States consumed 25% of the oil produced in 2007, the production, distribution and retailing of petroleum taken as a whole represents the worlds largest industry in terms of dollar value.
Petroleum is a naturally occurring liquid found in rock formations and it consists of a complex mixture of hydrocarbons of various molecular weights, plus other organic compounds. It is generally accepted that oil is formed mostly from the carbon rich remains of ancient plankton after exposure to heat, Petroleum in an unrefined state has been utilized by humans for over 5000 years. Oil in general has been used since early history to keep fires ablaze. Its importance to the world economy evolved slowly, with oil used for lighting in the 19th century and wood. The Industrial Revolution generated an increasing need for energy which was met mainly by coal, Imperial Russia produced 3,500 tons of oil in 1825 and doubled its output by mid-century. Batum is renamed to Batumi in 1936, at the turn of the 20th century, Imperial Russias output of oil, almost entirely from the Apsheron Peninsula, accounted for half of the worlds production and dominated international markets. Nearly 200 small refineries operated in the suburbs of Baku by 1884, as a side effect of these early developments, the Apsheron Peninsula emerged as the worlds oldest legacy of oil pollution and environmental negligence.
In 1846, Baku the first ever well drilled with percussion tools to a depth of 21 meters for oil exploration, in 1878, Ludvig Nobel and his Branobel company revolutionized oil transport by commissioning the first oil tanker and launching it on the Caspian Sea. Samuel Kier established Americas first oil refinery in Pittsburgh on Seventh avenue near Grant Street, one of the first modern oil refineries were built by Ignacy Łukasiewicz near Jasło, Poland in 1854–56. These were initially small as demand for refined fuel was limited, the refined products were used in artificial asphalt, machine oil and lubricants, in addition to Łukasiewiczs kerosene lamp
Scarp retreat is a geological process through which the location of an escarpment changes over time. Scarps may retreat for tens of kilometers in this way over relatively short time spans. A scarp is a line of cliffs that has usually been formed by faulting or erosion, if it is protected by a strong caprock, or if it contains vertical fractures, it may retain its steep profile as it retreats. Scarps in dry climates typically have a near-vertical upper face, that may account for 10% - 75% of the total height, the caprock is undermined as the rampart and face are eroded, and eventually a section collapses. A strong caprock will typically create a high cliff, since more undermining is needed to cause it to fail. Other factors determining how easily a cliff will fail are the bedding and jointing, direction of dip, a thin caprock will result in low cliffs that retreat quickly. The most common way in which a scarp retreats is through rockfall, in some high-energy situations, much of the rock may be powdered in a rockfall and easily eroded.
Generally, the fallen debris must be weathered and the rampart eroded before scarp retreat can continue and chemical weathering followed by wind erosion may operate in arid regions, where cliffs may retreat for long distances. In such regions, large areas of shale badlands may be left behind as the scarp retreats, erosion may be caused by the sea where the scarp runs along a coast, or by streams in humid areas. The rate of retreat depends on the types of rock and the factors causing erosion, retreat of the Great Escarpment in Australia along the river valleys in the New England region appears to be progressing at about 2 kilometres per million years. A study of cuesta scarp retreat in southern Morocco showed a rate of 1.3 kilometres per million years in areas with thin conglomerate caprocks. Where there were thicker, more resistant limestone caprocks the rate of retreat was slower, the Colorado Plateau has a cuesta scarp topography, consisting of slightly deformed strata of alternating harder and softer rocks.
The climate has been mostly dry throughout the Cenozoic, the conspicuous scarps on the plateau have massive sandstone caps over easily weathered rock such as shale. Freeze-thaw and groundwater sapping contribute to scarp retreat in this region, the Drakensberg mountains in South Africa are capped by a layer of Karoo basalts about 1,000 metres thick, which overlay Clarens formation sandstones. They have long considered a classic example of a landform created by scarp retreat following continental break-up. However, they have inland-facing scarps as well as seaward-facing scarps, lester Charles King Scarp retreat on planet Mars Citations Sources
They form the southern end of the Niagara Gorge. From largest to smallest, the three waterfalls are the Horseshoe Falls, the American Falls and the Bridal Veil Falls, the Horseshoe Falls lies on the border of the United States and Canada with the American Falls entirely on the American side, separated by Goat Island. The smaller Bridal Veil Falls are on the American side, the international boundary line was originally drawn through Horseshoe Falls in 1819, but the boundary has long been in dispute due to natural erosion and construction. Located on the Niagara River, which drains Lake Erie into Lake Ontario, Horseshoe Falls is the most powerful waterfall in North America, as measured by vertical height and flow rate. The falls are 17 miles north-northwest of Buffalo, New York, while not exceptionally high, the Niagara Falls are very wide. More than six cubic feet of water falls over the crest line every minute in high flow. The Niagara Falls are famed both for their beauty and as a source of hydroelectric power.
Balancing recreational and industrial uses has been a challenge for the stewards of the falls since the 19th century. The Horseshoe Falls drop about 188 feet, while the height of the American Falls varies between 70 and 100 feet because of the presence of giant boulders at its base. The larger Horseshoe Falls are about 2,600 feet wide, the distance between the American extremity of the Niagara Falls and the Canadian extremity is 3,409 feet. The volume of water approaching the falls during peak season may sometimes be as much as 225,000 cubic feet per second. The average annual rate is 85,000 cubic feet per second. Since the flow is a function of the Lake Erie water elevation. This is accomplished by employing a weir – the International Control Dam – with movable gates upstream from the Horseshoe Falls. The falls flow is further halved at night, during the low tourist season in the winter, water diversion is regulated by the 1950 Niagara Treaty and is administered by the International Niagara Board of Control.
The current rate of erosion is approximately 1 foot per year and it is estimated that 50,000 years from now, even at this reduced rate of erosion, the remaining 20 miles to Lake Erie will have been undermined and the falls will cease to exist. The features that became Niagara Falls were created by the Wisconsin glaciation about 10,000 years ago, the same forces created the North American Great Lakes and the Niagara River. All were dug by an ice sheet that drove through the area, deepening some river channels to form lakes
Sandstone is a clastic sedimentary rock composed mainly of sand-sized minerals or rock grains. Most sandstone is composed of quartz or feldspar because these are the most common minerals in the Earths crust, like sand, sandstone may be any color, but the most common colors are tan, yellow, grey, pink and black. Since sandstone beds often form highly visible cliffs and other topographic features, quartz-bearing sandstone is converted into quartzite through heating and pressure, usually related to tectonic compression within orogenic belts. They are formed from cemented grains that may either be fragments of a rock or be mono-minerallic crystals. The cements binding these grains together are typically calcite, grain sizes in sands are defined within the range of 0.0625 mm to 2 mm. The formation of sandstone involves two principal stages, first, a layer or layers of sand accumulates as the result of sedimentation, either from water or from air. Typically, sedimentation occurs by the settling out from suspension.
The most common cementing materials are silica and calcium carbonate, which are derived either from dissolution or from alteration of the sand after it was buried. Colours will usually be tan or yellow, a predominant additional colourant in the southwestern United States is iron oxide, which imparts reddish tints ranging from pink to dark red, with additional manganese imparting a purplish hue. Red sandstones are seen in the Southwest and West of Britain, as well as central Europe. The regularity of the latter favours use as a source for masonry, either as a building material or as a facing stone. These physical properties allow the grains to survive multiple recycling events. Quartz grains evolve from rock, which are felsic in origin. Feldspathic framework grains are commonly the second most abundant mineral in sandstones, Feldspar can be divided into two smaller subdivisions, alkali feldspars and plagioclase feldspars. The different types of feldspar can be distinguished under a petrographic microscope, below is a description of the different types of feldspar.
Alkali feldspar is a group of minerals in which the composition of the mineral can range from KAlSi3O8 to NaAlSi3O8. Plagioclase feldspar is a group of solid solution minerals that range in composition from NaAlSi3O8 to CaAl2Si2O8. Lithic framework grains are pieces of ancient source rock that have yet to weather away to individual mineral grains, accessory minerals are all other mineral grains in a sandstone, commonly these minerals make up just a small percentage of the grains in a sandstone
Calcite is a carbonate mineral and the most stable polymorph of calcium carbonate. The Mohs scale of hardness, based on scratch hardness comparison. Other polymorphs of calcium carbonate are the minerals aragonite and vaterite, aragonite will change to calcite at 380–470 °C, and vaterite is even less stable. Calcite is derived from the German Calcit, a term coined in the 19th century from the Latin word for lime and it is thus etymologically related to chalk. Calcite crystals are trigonal-rhombohedral, though actual calcite rhombohedra are rare as natural crystals, they show a remarkable variety of habits including acute to obtuse rhombohedra, tabular forms, prisms, or various scalenohedra. Calcite exhibits several twinning types adding to the variety of observed forms and it may occur as fibrous, lamellar, or compact. Cleavage is usually in three directions parallel to the rhombohedron form and its fracture is conchoidal, but difficult to obtain. It has a defining Mohs hardness of 3, a gravity of 2.71.
Color is white or none, though shades of gray, orange, green, violet, calcite is transparent to opaque and may occasionally show phosphorescence or fluorescence. A transparent variety called Iceland spar is used for optical purposes, acute scalenohedral crystals are sometimes referred to as dogtooth spar while the rhombohedral form is sometimes referred to as nailhead spar. Single calcite crystals display an optical property called birefringence and this strong birefringence causes objects viewed through a clear piece of calcite to appear doubled. The birefringent effect was first described by the Danish scientist Rasmus Bartholin in 1669, at a wavelength of ~590 nm calcite has ordinary and extraordinary refractive indices of 1.658 and 1.486, respectively. Between 190 and 1700 nm, the refractive index varies roughly between 1.9 and 1.5, while the extraordinary refractive index varies between 1.6 and 1.4. Calcite, like most carbonates, will dissolve with most forms of acid, calcite can be either dissolved by groundwater or precipitated by groundwater, depending on several factors including the water temperature, pH, and dissolved ion concentrations.
Although calcite is fairly insoluble in water, acidity can cause dissolution of calcite. Ambient carbon dioxide, due to its acidity, has a slight solubilizing effect on calcite, calcite exhibits an unusual characteristic called retrograde solubility in which it becomes less soluble in water as the temperature increases. When conditions are right for precipitation, calcite forms mineral coatings that cement the existing rock grains together or it can fill fractures. On a landscape scale, continued dissolution of calcium carbonate-rich rocks can lead to the expansion and eventual collapse of cave systems, high-grade optical calcite was used in World War II for gun sights, specifically in bomb sights and anti-aircraft weaponry
An escarpment is a steep slope or long cliff that forms as an effect of faulting or erosion and separates two relatively level areas of differing elevations. Usually escarpment is used interchangeably with scarp, but some sources differentiate the two terms, where escarpment refers to the margin between two landforms, while scarp is synonymous with a cliff or steep slope. The surface of the slope is called a scarp face. This is a ridge which has a gentle slope on one side. Scarps are generally formed by one of two processes, either by differential erosion of rocks, or by vertical movement of the Earths crust along a geologic fault. Most commonly, an escarpment is a transition from one series of rocks to another series of a different age. Escarpments are formed by faults. When a fault displaces the ground surface so that one side is higher than the other and this can occur in dip-slip faults, or when a strike-slip fault brings a piece of high ground adjacent to an area of lower ground. More loosely, the term describes the zone between coastal lowlands and continental plateaus which have a marked, abrupt change in elevation caused by coastal erosion at the base of the plateau.
Earth is not the planet where escarpments occur. They are believed to occur on other planets when the crust contracts, on other Solar System bodies such as Mercury and the Moon, the Latin term rupes is used for an escarpment. When sedimentary beds are tilted and exposed to the surface, escarpments erode gradually and over geological time. The mélange tendencies of escarpments results in varying contacts between a multitude of rock types and these varying levels of erosion can lead to strange features forming in the exposed rock. Kinver Edge The Lincoln Edge Stanage Edge Wenlock Edge France La Côte dOr is famous for its wines and has given its name to a département, le Pays de Bray, a clay vale enclosed by chalk escarpments
Mafic is an adjective describing a silicate mineral or igneous rock that is rich in magnesium and iron, and is thus a portmanteau of magnesium and ferric. Most mafic minerals are dark in color, and common rock-forming mafic minerals include olivine, amphibole, common mafic rocks include basalt and gabbro. Mafic rocks often contain calcium-rich varieties of plagioclase feldspar, mafic rocks are on the other side of the rock spectrum from the felsic rocks. The term roughly corresponds to the basic rock class. Mafic lava, before cooling, has a low viscosity, in comparison to felsic lava and other volatiles can more easily and gradually escape from mafic lava. As a result, eruptions of volcanoes made of mafic lavas are less violent than felsic-lava eruptions. Most mafic-lava volcanoes are shield volcanoes, like those in Hawaii, QAPF diagram List of minerals List of rock types
Anhydrite is a mineral—anhydrous calcium sulfate, CaSO4. It is in the crystal system, with three directions of perfect cleavage parallel to the three planes of symmetry. It is not isomorphous with the orthorhombic barium and strontium sulfates, distinctly developed crystals are somewhat rare, the mineral usually presenting the form of cleavage masses. The Mohs hardness is 3.5 and the gravity is 2.9. The color is white, sometimes greyish, bluish, or purple, on the best developed of the three cleavages, the lustre is pearly, on other surfaces it is glassy. When exposed to water, anhydrite readily transforms to the commonly occurring gypsum. This transformation is reversible, with gypsum or calcium sulfate hemihydrate forming anhydrite by heating to around 200 °C under normal atmospheric conditions, anhydrite is commonly associated with calcite and sulfides such as galena, chalcopyrite and pyrite in vein deposits. Anhydrite is most frequently found in deposits with gypsum, it was, for instance, first discovered, in 1794.
In this occurrence, depth is critical since nearer the surface anhydrite has been altered to gypsum by absorption of circulating ground water and this is one of the several methods by which the mineral has been prepared artificially, and is identical with its mode of origin in nature. The mineral is common in salt basins, anhydrite occurs in a tidal flat environment in the Persian Gulf sabkhas as massive diagenetic replacement nodules. Cross sections of these nodular masses have an appearance and have been referred to as chicken-wire anhydrite. Nodular anhydrite occurs as replacement of gypsum in a variety of depositional environments. Massive amounts of anhydrite occur when salt domes form a caprock, anhydrite is 1–3% of the salt in salt domes and is generally left as a cap at the top of the salt when the halite is removed by pore waters. The typical cap rock is a salt, topped by a layer of anhydrite, topped by patches of gypsum, interaction with oil can reduce SO4 creating calcite and hydrogen sulfide.
Anhydrite has been found in igneous rocks, for example in the intrusive dioritic pluton of El Teniente, Chile and in trachyandesite pumice erupted by El Chichón volcano. The name anhydrite was given by A. G. Werner in 1804, because of the absence of water of crystallization, as contrasted with the presence of water in gypsum. Some obsolete names for the species are muriacite and karstenite, the former, the Catalyst Science Discovery Centre, has a relief carving of an anhydrite kiln, made from a piece of anhydrite, for the United Sulphuric Acid Corporation
The Niagara Escarpment is a long escarpment, or cuesta, in the United States and Canada that runs predominantly east/west from New York, through Ontario, Michigan and Illinois. The escarpment is most famous as the cliff over which the Niagara River plunges at Niagara Falls, the Niagara Escarpment is the most prominent of several escarpments formed in the bedrock of the Great Lakes Basin. From its easternmost point near Watertown, New York, the escarpment shapes in part the individual basins and landforms of Lakes Ontario, Huron, in Rochester, New York, three waterfalls over the escarpment are where the Genesee River flows through the city. The escarpment thence runs westward to the Niagara River, forming a gorge north of Niagara Falls. Study of rock exposures and drillholes demonstrates that no displacement of the rock layers occurs at the escarpment, the escarpments caprock is dolomitic limestone, which is more resistant and overlies weaker, more easily eroded shale as a weathering-resistant cap.
The escarpment thus formed over millions of years through a process of erosion of rocks of different hardnesses. Through time the soft rocks weather away or erode by the action of streams, the gradual removal of the soft rocks undercuts the resistant caprock, leaving a cliff or escarpment. The erosional process is most readily seen at Niagara Falls, where the river has quickened the process and it can be seen at the three waterfalls of the Genesee River at Rochester. Also, in places thick glacial deposits conceal the Niagara Escarpment, such as north of Georgetown, Ontario. The dolostone cap was laid down as sediment on the floor of a marine environment, in Michigan, behind the escarpment, the cuesta capstone slopes gently to form a wide basin, the floor of an Ordovician-Silurian-age tropical sea. During the Silurian period, some magnesium substituted for some of the calcium in the carbonates, worldwide sea levels were at their all-time maximum in the Ordovician, as the sea retreated, erosion inevitably began.
This dolostone basin contains Lakes Michigan and Erie, the Welland Canal allows ships to traverse the escarpment between Lake Erie and Lake Ontario on the Niagara Peninsula of Ontario. In southern Ontario, the Bruce Trail runs the length of the escarpment from Queenston on the Niagara River to Tobermory on the Bruce Peninsula. Highway 401, Canadas busiest, crosses the Niagara Escarpment, beginning its descent through rolling hills, farmland. Rock exposed on the face of the escarpment can be seen along Highway 26 from Owen Sound eastwards towards Meaford, Ontario, is situated on the escarpment in such a way that the north end of the city is below and the south part above. Affectionately referred to as The Mountain by its residents, many roads or mountain accesses join the urban core below with the suburban expansion above. High Cliff State Park in Wisconsin shows how modern and prehistoric humans used the escarpment for not only cultural reasons, a number of different animal and geometric effigy mounds and the remains of an early 20th-century limestone quarry and kiln are within the park.
The relief and exposed edge are used by wind farms stretching from Pipe, Wisconsin, to Brownsville