Delta

A DELTA IS AN AREA of land that has been built up at the mouth of a river, where it flows into a quiet body of water, such as a lake or an ocean. The delta is formed when the river, which is moving swiftly and carrying sediment such as mud, slows down to enter the larger body of water. At the slower speed, the water can’t carry as much sediment, so most of it is dropped onto the bottom of the ocean. It builds up layer by layer, over a long period of time, until it is above the surface of the water.

The delta builds up at the end of the river itself, since it cannot rise higher than the surface of the ocean. As more and more sediment is deposited, the delta grows in size and extends further upstream. The more mud the river carries, the faster a delta will build up. Most deltas have a roughly triangular shape. The name came from the Greek letter delta, which is shaped like a triangle. If plants grow on the delta, their roots and remains become part of the soil, enriching it. A delta is an ever-changing landform. If the original channel of the river is filled with sediment, the stream will overflow across the surface of the delta, dividing into smaller streams or channels called distributaries.

The size and shape of the delta depends on several factors. If the waves are strong where the river enters the ocean, any deposits will be washed away and a delta will not form. The weaker the waves in the ocean at that point, the more the delta will build up. Delta formation is also dependent upon the amount of material being carried by the river. If waves are not very strong, the delta will grow rapidly, with long fingers of land building up along the distributaries. This is called a bird’s-foot delta.

Throughout history, deltas have been important to civilizations. The soil of a delta is usually very fertile and is good for farming. Delta lands often flood every year, spreading another layer of silt. Many deltas have unhealthful climates and poor drainage, but still tend to support dense populations of people. All over the world, deltas have influenced the lives of people. Some of the most important deltas include the MISSISSIPPI RIVER delta, the NILE RIVER delta, and the delta of the GANGES river.

The Mississippi River delta is located at the southern edge of the UNITED STATES, where the Mississippi River empties into the Gulf of Mexico. South of New Orleans, LOUISIANA, a bird’s-foot delta has built up. The resulting valley provides habitat for many species of plants and animals important to the ecology of the area. Farms on the delta produce much of the country’s supply of soybeans, rice, sugarcane, and cotton. The Mississippi River still deposits sediment on the delta. In some places, more than 98 ft (30 m) have been deposited in the last 100 years.

The Nile delta is located at the northern end of the Nile River, where it flows into the MEDITERRANEAN SEA in EGYPT. The Nile is the longest river in the world. Most of the delta’s surface is covered with crops, contrasting sharply with the barren desert around it. Cairo, the capital of EGYPT, is an example of a delta supporting a dense population. The city has a population of more than 11 million people, which is more than 26,000 people per .386 square mi (1 square km). At its widest, the delta is about 153 mi (250 km) wide along the Mediterranean.

The Ganges-Brahmaputra delta was created by sediments deposited by these two great rivers in the area of BANGLADESH. People have built their homes on artificially raised earthen hills to protect them from the yearly floods. Like the Nile delta, this region is overpopulated. Population density far exceeds 500 people per .386 square mi (1 square km). Over 300,000 people were killed by floods there in 1991. Farming is almost the sole occupation on this delta.

Delmarva Peninsula

THE 5,940-square-mi (15,384 square km) Delmarva Peninsula is located in the mid-Atlantic area of the UNITED STATES and borders the Chesapeake Bay, the Delaware Bay and the ATLANTIC OCEAN. The historic importance of the area is that it formed an important political and social demarcation between the North and the South of the United States: the Mason Dixon Line.

The border between MARYLAND and DELAWARE formed the initial portion of the Mason-Dixon line, drawn in the mid-1700s to settle a boundary dispute between the Calvert family and the Penn family. The Mason-Dixon line later became the delineation between northern states and southern states, and therefore between slave states and free states. The name Delmarva comes from letters in the state names that share it, including all of DELaware, and portions of MARyland, and VirginiA.

Compared to the rest of the United States, the Delmarva Peninsula is strikingly flat, with most of the area approximately 30 ft (9 km) above sea level. Interestingly, this area was not always flat. Two hundred million years ago, the APPALACHIAN MOUNTAINS were the edge of the ocean. The shoreline itself then was rocky, resembling a steeper version of the current coast of MAINE. The long, flat, sandy beaches that characterize today’s Delmarva coastline emerged because of continental drift. The Appalachians have been moving westward for 245 million years, and they’ve been doing it at a yearly rate that just about equals the speed at which fingernails grow. As the Appalachians were drifting westward, they also eroded. Their rocks were weathered into sand. This sand was carried by streams and rivers to the coast and deposited. Over time, these deposits, once under water, have been exposed and now form the coastal beaches.

CHANGING GEOGRAPHY

Today, coastal currents and storms are changing the geography again. This can be seen even in maps of the area between the coastal towns of Rehoboth and Cape Henlopen. These show that since 1878, the shoreline has moved almost 1,200 ft (366 m) inland. The wide sandy beaches of Delmarva are a major tourist destination and a major economic resource for the area. Maryland’s heavily developed Ocean City has a yearround population of less than 10,000, but during peak summer weekends, the population swells to more than 300,000.

With a shallow and changing coastline and a lack of natural harbors and energy resources, Delmarva did not become heavily industrialized as did some of its neighboring areas. Today, intensive truck gardening agriculture, poultry farming, and the seafood industries form the backbone of the peninsula’s economy. Its strategic location, just a few hours from Baltimore, Washington, D.C., and Philadelphia, with overnight access to almost one-third of the nation’s population, have made it a major food supplier for the East Coast of the United States.

Delaware

DELAWARE IS ONE OF the Middle Atlantic states of the UNITED STATES. It is also the country’s second smallest state after RHODE ISLAND, covering 2,057 square mi (5,328 square km) within the DELMARVA PENINSULA. It is bordered by MARYLAND on the west and south, NEW JERSEY to the northeast across the Delaware Bay and Delaware River, and there is a short border with PENNSYLVANIA in the north. The state’s 783,600 residents (2000) share their part of the peninsula with Eastern Shore Maryland and VIRGINIA. The area is part of the Atlantic Coastal Plain, which runs for more that 2,200 mi (3,667 km) from Cape Cod to the Gulf of Mexico.

The countryside is relatively flat, with the land rising gently from sea level in the areas along the eastern shore to 442 ft (135 m) in the Piedmont region along the border with Pennsylvania. The southern part of the state is mostly swampland. A number of small rivers flow across the state, flowing either east to the Delaware (the Christina and Brandywine) or west across Maryland to the Chesapeake Bay (the Nanticoke). The state capitol is in Dover, although Wilmington is the largest city with 72,664 residents.

When Henry Hudson sailed into the Delaware Bay for the Dutch East India Company in 1609, he found the area of sand dunes, swamps, and gently rolling hills inhabited by Native Americans (Nanticoke and Minqua). Although both English and Dutch interests vied for the region, the Dutch established the first settlement in 1631. Within a year, however, that settlement was destroyed by a rare Native American attack. For the most part, the area’s Native Americans were friendly and open to trade and within a short time several Dutchman interested in settling the area received permission to colonize the area for Sweden. Peter Minuit, one of the more notable of the early settlers, led the expedition for the Swedes, organizing New Sweden and founding Fort Christina on the site of today’s Wilmington in 1638. Following a number of battles among the English, Dutch, and Swedes, the area was finally turned over to England in 1674, where it remained until the American Revolution. The Colony of Delaware became a state in 1776 and was the first state to ratify the new Constitution of the United States in 1787.

By the end of the 18th century industry was making inroads in Delaware. In the Piedmont region of the north with the rolling wooded hills, the Brandywine and Christina rivers provided ideal locations for gristmills to grind grain into flour. At the same time, Wilmington became a center for the manufacture of cloth, paper, and flour products, an industrial sector that flourished into the 19th century. The Du Pont family established a gunpowder mill on the Brandywine River in 1802, marking the beginning of what would become one of America’s most successful family business empires.

More recently, the finance and insurance sectors have become increasingly significant employment and income generators, although manufacturing and agriculture are still important. The manufacturing, credit card, banking, and insurance industries are heavily concentrated in the north. Broiler chickens, soybeans, corn, and dairy products comprise the heart of a still vibrant agricultural sector, utilizing lands generally below the Chesapeake and Delaware Canal in the south. Potatoes and other vegetables are also grown; in addition there is a small fishing industry centered on harvests of clams, menhaden, oysters, and scup.

Because Delaware has some of the more lenient laws regulating business taxation and practice, the state is home to many of the largest corporations in the United States. This is especially true for those in the banking and financial services sectors, and these now dominate the state’s economy. The chemicals and materials monopoly that was founded by the Du Pont family in the 19th century, despite being broken up by the government in an antitrust suit in 1912 and losing another suit in the 1950s over the firm’s major interest in General Motors, continues to be one of the largest corporations in the world. In addition to chemicals and chemical products, the biomedical, apparel, processed foods, rubber and plastic products, and transportation equipment industries are important and contribute to the state’s wealth.

Deccan Plateau

LOCATED IN INDIA, in the southern part of the peninsula south of the Indo-Gangetic Plain, the Deccan Plateau can be considered the cultural and historical heart of India, defining the subcontinent. The great epic poems of the Vedas tell of the coming of the Aryan-speaking peoples that dominate all of northern Indian today. However, the very peoples they supplanted did not disappear but were concentrated in the Deccan and maintained distinctive cultures and language groups.

Remnants of a predominantly indigenous Dravidian culture (pre-Aryan) exist in the Tamil kingdoms found by the ancient Greeks. Tamil literature from 300 B.C.E. records the social life and academic accomplishments of these peoples. Three great Tamil dynasties emerged and challenged one another in internecine fighting. The rise of Buddhism in north India did reach into the Deccan, but the south remained resistant to the kings and Moguls that came in history’s wake. Islam never made significant inroads into the Deccan Plateau. The coming of the Europeans from the 15th century onward gradually affected the coastal areas and even the interior Deccan gave way under the British raj (ruler). Characteristic of their distinct culture and history, many calls for independent states have arisen since the establishment of the Indian Union in 1947.

The Deccan Plateau is believed to be an ancient remnant of the Earth’s original continent, Gondwanaland, which broke up to create the continents we know today. The plateau is a great ancient shield of basalt lava that now bears the scars of its long exposure to the weathering effects of wind and water. The Vindhya Range marks the margins of the southern reaching peninsula and the Indo-Gangetic Plain. The Deccan is uplifted between 2,625 and 4,600 ft (800 and 1,400 m). The western Ghats increase in average height as they go south, reaching a maximum of 8,842 ft (2,695 m) in Kerala. The narrow coastal plain between the western Ghats and the ARABIAN SEA is marked by lagoons and backwaters. The plateau is primarily drained to the east with the headwaters of the Krishna, Bhima, and Godavari forming in the western Ghats and flowing up to 3,280 mi (1,000 km) eastward across the plateau to the BAY OF BENGAL. The eastern coastal plain is much broader and marked by the deltas of the Godavari, Mahanadi, and Kaveri rivers. The central Deccan is a series of smaller plateaus topped with rolling hills and dissected by many watercourses.

The monsoon cycle of dry and wet seasons affect the entire peninsula. The plateau has sparse but continuous dry deciduous forests across its southern third and along the eastern Ghats. To the north and in the central portions, the forest gives way to scrubland. Over 300 million people live in the greater area of the Deccan Plateau. Sustainable resources such as forests and water are under increasing pressure. Deforested areas are being replanted with extensive monoculture that will further deplete the diversity of the ecosystem. Silting of reservoirs has been a historic problem and accelerated damming of water courses bodes ill for the long-term management of the various watersheds. Mining of the Deccan rich mineral deposits has not modernized. Techniques for the full recovery of the potential ore, management of overburden removal, and control of toxic wastes are all required.

Dead Sea

THE DEAD SEA IS a 390-square-mi (1,010-squarekm) salt lake located on the borders of PALESTINE, ISRAEL, and JORDAN. It is the lowest water point in the world, and its coast, at 1,292 ft below sea level (-395 m), is the lowest dry point on Earth. The lake is divided into two unequal parts by el-Lisan or “the Tongue,” which is a wide peninsula jutting from the lake’s southeastern shore. The northern part is larger and deeper, reaching 1,300 ft (400 m) in depth. In contrast, the southern side reaches only 35 ft (11 m) and averages only 13 ft (4 m) in depth.

The Dead Sea formed when two plates of the Earth’s crust began spreading apart, creating a low region, the Rift Valley system, where the crust is stretched quite thin. The Dead Sea is located in the region where the Earth’s surface has sunk, and the lake’s bottom is still sinking, as much as 13 in (33 cm) annually, an incredibly fast rate. In contrast, on the eastern and western sides of the lake, looming mountains range from 2,500 to 4,000 ft (762 to 1219 m) in height. The Jordan River is on the lake’s north, and hills of solid salt (Jebel Usdum or Mount Sodom) rise up on its southern border. Lower than surrounding topography, the Dead Sea is fed over 6.5 million tons of fresh water by the Jordan River and smaller streams every single day. (It should be noted that large scale Israeli and Jordanian irrigation projects along the Jordan River have been causing the depth of the Dead Sea to decrease over the past 50 years; pollution is a concern.)

Because the lake has no outlets and is completely LANDLOCKED, the only way that water leaves is through evaporation; because the Dead Sea is located in a hot area with low precipitation, water evaporates to the degree that the sea level seldom fluctuates, other than because of irrigation, and what is left behind is the salt. Twenty-seven percent of the Dead Sea consists of solid substances, including sodium chloride, magnesium chloride, calcium chloride, potassium chloride and magnesium bromide. Potash, bromine, gypsum, salt and other products are commercially extracted from these waters, which become saltier as depth increases.

At about 130 ft (40 m), there are approximately 300 grams of salt per kilogram of water, which is about 10 times the saltiness of typical ocean water. Once the depth is greater than 300 ft (91 m), there are 332 grams of salt per kilogram, which is a state of saturation and explains the piles of salt found at the lake’s bottom. Due to this extreme saltiness, the Dead Sea supports no plant, animal, or fish life. If a fish swims from a stream into this lake, it is instantly killed and then preserved by the lake’s mineral salts. The only types of life, then, existing in the Dead Sea are microbes and highly specialized algae; on occasion, a seabird is seen resting on the lake’s surface.

Humans can swim in Dead Sea waters, but because of the extraordinarily high salt concentration and density of the water, the experience is more like floating. When a person exits the lake, the body is coated with white salts, just as the shores of the Dead Sea are covered with this substance, and the person’s skin can become irritated. The salts can irritate the eyes, and the water, if swallowed, tastes revolting because of the chloride of magnesium. Chloride of calcium gives the water its oily appearance.

The name Dead Sea is used in the Old Testament, although other biblical names are also listed for this body of water, including the Salt Sea, East Sea, Sea of the Plain, and Sodomitish Sea; the ancient cities of Sodom and Gomorrah were located at the lake’s southwestern coast. Yet another name is the Lake of Asphalt, given because of the quantities of bitumen that rise to the surface of this lake, and current inhabitants call this body of water the Sea of Lot.

This region is famous for the Dead Sea Scrolls found in 11 caves in nearby Qumran from 1947 to 1956. Literally thousands of Biblical fragments and ancient Jewish documents were found, which added greatly to the understanding of these religions. Today, the shores of the Dead Sea contain popular beaches, resorts, and spas.

Darien Gap

STRADDLING THE BORDER of the republics of PANAMA and COLOMBIA, the Darien Gap is home to one of the least exploited and most diverse ecosystems in the world. Flanked by the PACIFIC OCEAN to the north and west and the CARIBBEAN SEA to the east, the area includes two national parks, Darien National Park in Panama and Los Katios National Park in Colombia.

The area is 30 mi or 50 km wide, from the North Pacific Ocean to the Caribbean Sea, and 54 mi or 84 km in length, when measuring from the terminus city of Yarviza in Panama to Lomas Aisiadas in Colombia. The Darien Gap harbors varying landforms, from swamplands on the Colombian side to the mountainous rainforests with its tallest peak, Cerro Tacarcuna (standing at 5,535 ft or 1,845 m), on the Panamanian side. With more than 3 million acres of wilderness, the ecosystem found within is one of the most hotly contested, a political and environmental quagmire.

The Pan-American Highway, stretching approximately 16,000 miles or 26,000 km from ALASKA in the UNITED STATES to the Tierra del Fuego region of CHILE in South America, is broken only by the natural barrier of the Darien Gap. Initial plans to construct a road through the Darien Gap commenced in 1923 at the Fifth International Conference of American States.

One of the primary reasons for the road is that through its completion, trade between North and Central America and South America would be more efficient with less reliance on the Panama Canal as the primary thoroughfare. Past opponents conferred that the spread of aftosa, or commonly known as foot-andmouth disease, would possibly be spread from the cattle of Colombia to Central and North America if the road were built.

In 1991, the U.S. Department of Agriculture proclaimed this threat to be extinct. Road construction began in 1971 and lasted until 1974, when further construction was halted due to environmental concerns. During that time period, part of the area was officially put under protection through decree no. 84 for the Alto Darien Protection Forest. Since that time, the area was designated as a World Heritage Site as well as a United Nations-designated Man and Biosphere Reserve. The area is home to two major tribes and several smaller ones. The subsistence agricultural lifestyle of the Chocos (both Emberas and Vainanas) and the Kunas is threatened, as it will be a potential loss of their land and culture if the road through the Darien Gap comes to fruition.

The route has been fully surveyed and partially completed, yet the political, economic, and environmental issues surrounding its construction are the true barriers to its completion. The approximate costs for completion would be approximately $200 million. Effective lobbying by environmental and indigenous groups, costs associated with the road infrastructure, governmental bureaucracy, and the de facto control of the area by Colombian rebel groups have left the fate of the remaining 54 mi or 84 km of road in limbo.

Widely publicized accounts of civilian kidnappings, drug-smuggling anarchy, and the controlling activities of Colombian rebel groups have made this area one of the most dangerous in the world.

Danubian Gates

FOR CENTURIES, traffic along the DANUBE RIVER was hindered by a stretch of treacherous rocks and narrow gorges at the point at which the river cut through the Southern Carpathian mountain range. This stretch, about 62 mi (100 km) in length, along the border of ROMANIA and Yugoslavia (SERBIA), is known as the Danubian or Iron Gates, “Portile de Fier” in Romanian, and “Djerdap” in Serbian.

This barrier long formed a boundary between lower river commerce (to the BLACK SEA), and the river traffic of the upper Danube basin. The river flows through crystalline schists, limestones, and Sinaia strata (local Romanian stone), with both dangerous rock outcroppings in the riverbed, dangerous curves, and intense currents as the gorge reaches its narrowest points. The waters were most dangerous during low water periods (summer and autumn), and especially at night, when the height and verticality of the gorge walls allowed for extremely limited visibility.

Man added further dangers over the centuries, with nearly impregnable fortresses built by robber barons and extortionist princes. Most famous of these was the fortress Tri Kule, near Svinita, built by a Transylvanian prince to prevent Turkish infiltrations into the middle and upper Danube areas. But commerce continued. A system of mule tracks and rope attachments were long in operation to drag boats through the area, and as the region freed itself from Turkish rule, several large channel- cutting projects were attempted, most notably by Serbia in 1890–98, with the construction of a series of canals between Virciorova and Gura Vaii, the most dangerous section of the gorges, which introduced the use of trains to pull boats upstream instead of mules.

Other projects included the Sip Channel, underwater rock blasting, transverse and longitudinal embankments, beacons, signals, and so forth. But along with this challenge of commercial transport, governments of the region realized the potential for hydropower also provided by such a concentration of water in a narrow space. More than two-thirds of the Danube basin as a whole lies above the Iron Gates, with a catchment area of 219,089 square mi (567,440 square km) from the Alpine, Dinaric, and Carpathian zones, producing an average flow of 194,936 cubic ft (5,520 cubic m) per second. The Iron Gates Navigational Authority was established in 1948 by Yugoslavia and Romania to examine both issues of facilitated transport and development of hydropower potential. 

In 1956, this body set out initial plans to build a “hydro-energetical navigational system.” Work was

begun in 1964, and full operation began in 1971. This remains the largest hydropower dam and reservoir system along the entire Danube, but as western institutions have begun to have closer access to the region, some wider issues have been raised, notably concerning the system’s environmental impact, including upriver silting, downriver erosion, loss of animal habitat and worsening water quality.