Arizona

A PLACE OF indisputable geographical interest in the U.S. Southwest, of which the GRAND CANYON of the Colorado River is but the leading example, Arizona currently exemplifies a trend toward urbanization in western states. While much of Arizona’s land area of 113,635 square mi (294,315 square km) remains undeveloped, Arizona’s capital and largest city, Phoenix, alone accounts for more than a quarter of the state’s total population of 5,130,632 (2000 U. S. census).

Arizona was the last of the contiguous UNITED STATES to be granted statehood, in 1912. Statehood followed a long territorial history, beginning with the combination of a portion of the land area ceded to the United States by MEXICO in 1848 and the Gadsden Purchase of 1853 in the Territory of New Mexico. Arizona was organized as a separate territory in 1863. The state is bounded by UTAH, NEW MEXICO, CALIFORNIA, and NEVADA, and by Mexico to the south. The propriety of including the extreme northwestern land area, known as the Arizona strip, has long been a matter of dispute with adjoining Utah, due to its relative inaccessibility from greater Arizona across the Colorado River.

Three physiographic provinces divide the state into a continuity of diverse regions. To the north, the Colorado Plateau Province rises to a maximum altitude at Humphreys Peak (12,633 ft or 3,851 m). Composed primarily of Paleozoic sedimentary strata, the plateau is joined from several interlocking uplifted blocks, terminating on the southern boundary at the Mogollon Rim. The Grand Canyon cuts through the southwestern corner of the plateau, exposing a vast geological column that terminates in pre-Cambrian gneiss at the level of the Colorado River. Volcanic activity, seen in a field of cinder cones to the south of the canyon, has been recent; Sunset Crater, a cinder cone northeast of Flagstaff, is less than 1,000 years old. South of the Mogollon Rim are the Central Highlands, a province that is also termed the Transition Zone because the province shares characteristics of the Colorado Plateau and of the Basin and Range to the south and west. The southern and western extents of Arizona are the Basin and Range Province, a region of mountain ranges composed of volcanic rocks, separated by deep grabbens choked with alluvium.

Most of the Basin and Range Province is arid and is classified as desert. The SONORAN DESERT, which dominates the province and continues into Mexico and California, has two seasons of rainfall—in summer and winter—in its central portion, known as the Arizona Upland. This biannual rainfall provides up to ten inches of precipitation annually, making the Arizona Upland the most lush of American desert landscapes. Its unique plants include the saguaro, a columnar cactus that can reach 50 ft (15 m) in height. High temperatures in summer easily reach into the 110s degrees F (40s degrees C) in portions of the region. Because of its altitude, the Colorado Plateau enjoys a more moderate climate, although it too is arid. In a swath that crosses the Grand Canyon and extends along the Mogollon Rim above 6,000 ft (1,800 m), ponderosa pine form the largest continuous forest of this species in the United States. Winter snowfall is common on the plateau but can occur throughout the state, infrequently in the mountains surrounding Tucson in the south.

Arctic Ocean

THE ARCTIC is the smallest and shallowest of the Earth’s five oceans, occupying 4 percent of the world’s ocean space and surrounding the North Pole, the northernmost locale on the planet. The waters of the Arctic are fairly equidistant around the area, making the North Pole the approximate center of the ocean.  The majority of the Arctic Ocean is found north of the ARCTIC CIRCLE, which is one of the five circles of latitude marked on maps. Everything north of this line is considered the Arctic region; this area is mostly water, but the northernmost parts of ALASKA, CANADA, RUSSIA, NORWAY, and a significant portion of GREENLAND are within its borders. Therefore, most—but not all—of the Arctic Circle is ocean; and most—but not all—of the Arctic Ocean is north of the Arctic Circle. Greek explorers of the late 300s B.C.E. discovered this ocean, with Pytheas reporting frozen waters located six days north of Britain. Ancient Greeks named these waters after the Arktos constellation found in extreme northern skies, a cluster of stars now known as Ursa Major or Great Bear. The average depth is 3,407 ft (1,038 m) and its deepest point north of Svalbard, Norway, is 17,881 ft (5,450 m). Although some of the ocean is not deep at all, the lowest point, Fram Basin, is -15,305 (-4,665 m) below sea level.

The lowest surface temperatures of the Arctic Ocean occur in February at -28 degrees F (-33 degrees C) and the highest in July at 29 degrees F (-2 degrees C); frozen precipitation averages 10 in (25 cm) annually and rarely melts. Because of constant cold, the central surface of the Arctic Ocean is covered with ice 10 ft (3 m) thick, and some ice can triple that thickness. During summer months, free-flowing water surrounds the ice; during the winter, ice thickness doubles and even extends to land adjacent to the ocean. Around June 22, the sun can still be seen on the horizon at midnight. This gives the region its nickname: Land of the Midnight Sun.

The Arctic connects with the ATLANTIC OCEAN by Greenland, and the Bering Strait merges the Arctic with the Pacific. The PACIFIC OCEAN is more than 13 times the size of the Arctic, but even the world’s smallest ocean is 5,440,000 square mi (14 million square km), with a coastline of 28,203 mi (45,389 km), making the Arctic nearly 1.5 times the size of the UNITED STATES. Two significant waterways also connect to the ocean: the Northwest Passage, which flows into the United

States and Canada; and the Northern Sea Route, which provides water to Norway and Russia.

The Arctic contains five continental shelves, which are areas of shallow, submerged land located along the edge of a coastline. When a continental shelf ends, there is generally a steep slope that descends into the largest portion of the ocean floor. One of these, the 900-mi (1,448-km) Siberian Shelf, is the largest continental shelf in the world; approximately 50 percent of the Arctic Ocean’s floor consists of this geological feature. An underwater ocean ridge divides the Arctic into two basins.

Much of this ocean contains icebergs, frozen waters broken off from glaciers formed on the land. Some, especially those that form on Ellesmere Island and then break off (calve) into the Chukchi Sea, are large enough to be considered ice islands and last for several years. Once the icebergs hit the relatively warmer waters of the northern Atlantic, however, they melt fairly quickly. Few icebergs hit the Pacific, blocked from proceeding by the Bering Strait. Fish, seals, walruses, and whales reside in these waters, and petroleum and natural gas is pumped out. The Arctic is also home to the only ocean bear on the planet. Because of the extreme cold and low sunlight in this region, this ocean is slow to adapt to or recover from environmental change; scientists are watching the thinning of its polar ice and debating the connection between global warming and the shrinkage.

This region also provides scientists with information about pollution. Since it generates little of its own contaminants, the increase of pollutants found in the area help measure the world’s increasing water and airborne toxicity.

Arabian Sea

THE ARABIAN SEA covers approximately 1,491,000 square mi (3,862,000 square km) and is located between the Arabian and Indian peninsulas in the northwestern area of the INDIAN OCEAN, bounded by INDIA, PAKISTAN, IRAN, OMAN, YEMEN, and the HORN OF AFRICA. The Arabian Sea has been the historic trade route from Occident to Orient since the dawn of commerce between the cradles of civilization. Dhows (sailing vessels) full of spices and slaves have given way to petroleum tankers and container ships, yet the trade continues unabated.

As early as the 8th century and onward, Arabian and Persian mariners learned to navigate this area by using prevailing winds and the surface currents generated by the summer and winter monsoons. For half the year (April–October), the winds in this region are from the southwest, reversing in the other half of the year. This monsoon (season) weather pattern dominates the region on land and sea, setting the pace of commercial activities and much of life.

Commercial fishing is a major activity in the Arabian Sea with the leading species fished being sardines, prawns, and mackerel. India accounts for 23.6 percent of its annual haul mostly from waters 6 to 9 mi (10 to 15 km) from the coast. Fishing stocks are being depleted because of a combination of overfishing and pollution along the Indian coast. Some 65 percent of all fish taken from the Arabian Sea continues to be from local fishermen in traditional boats as their single means of livelihood.

The overexploitation of fish stocks is mostly due to large fishing vessels operating illegally near the coast. The growth of regional populations, particularly India, will add pressure on the already challenged marine resources. This population increase and industrial development create major pollution problems. Industrial effluents contain heavy metals and chemical wastes. Pesticides and organic wastes flow untreated into the coastal waters from cities and agricultural land. Oil pollution from accidents and ballast dumping is on the increase. The nations that share the management and use of the Arabian Sea have no comprehensive plan for conservation and management of the resources or uses of this critical area of ocean.

Primary branches of the Arabian Sea are the Gulf of Oman, which joins it to the Persian Gulf via the Strait of Hormuz and the Gulf of Aden, which joins it with the Red Sea via the BAB EL MANDEB. There are no islands in the middle of the Arabian Sea, where depths average in excess of 9,800 ft (3,000 m). Deep water reaches close to the bordering lands except in the northeast, off Pakistan and India. The deepest known point in the Arabian Sea is at Wheatley Deep, where depths are more than 19,000 ft (5,800 m). The principal waterway draining directly into the Arabian Sea is the INDUS RIVER. Costal islands exist around the Arabian Sea and have proven significant for political and

military purposes.

The sea is of geostrategic interest as it is the transit route for a major portion of the world’s oil supply. In addition, the commerce flowing by ship from Asia to Europe also sails this sea.

Aquifer

AN AQUIFER IS a subsurface structure or formation that provides a sufficiently permeable condition to yield significant quantities of water to wells and springs. Soil water movement is determined by two factors: porosity, which is the ability to hold on to water particles, and permeability, which is concerned with movement. The word aquifer comes from two Latin words: aqua, or “water,” and ferre, “to bear or carry.”

Aquifers literally carry water underground. Precipitation or meteoric water migrates its way downward through the pores or cracks in the soil. Beneath the soil surface is the zone of aeration in which the smaller openings contain a little water and the larger spaces usually contain air. Often soil particles are thinly covered with hygroscopic water, while capillary water is held close to the surface for plant needs.

Excess water will infiltrate by gravity to a point where all the spaces are filled with groundwater, which begins the zone of saturation. The top of this layer is called the water table and it will fluctuate depending upon precipitation or draw down. Aquifers are moderately to highly permeable layers of rock in which groundwater is stored or through which it moves. The formation may be a layer of gravel or sand, a layer of sandstone or cavernous limestone, a rubbly top or base of lava flow, or even granite fractured by ancient ice sheets. Some rock, such as clay or solid granite, may have only a few hairline cracks through which water can move, making them poor aquifers. In terms of storage at any one given time, groundwater is the largest single supply of fresh water available for use. It is estimated that it is more than 30 times greater than all the water stored in streams, rivers and freshwater lakes, yet most of it is not easily accessible.  The largest aquifer in the UNITED STATES is the Ogallala, which underlies the land from SOUTH DAKOTA to northern TEXAS.

Rainwater that migrates downward directly to the water table creates an unconfined aquifer, which may be shallow and therefore susceptible to contamination from industrial landfills, agricultural chemical runoff, sewer leakage, faulty septic tank operation, or even salt-water intrusion in coastal areas. A confined aquifer occurs when water is stored beneath a blocking stratum or aquiclude that stops the direct movement of gravitational water to it, allowing water to migrate over long distances, taking years or even centuries. The quality of groundwater is determined by the depth of the aquifer as bacterial or human pollution can be screened out by the rocks and soil. Water from a confined aquifer will tend to be freer of dangerous materials.

However, water is a solvent and may also have dissolved minerals. The most likely of these are sodium, calcium, magnesium, potassium, chloride, bicarbonate and sulfate, which are picked up in its movement. Water typically is not considered desirable for drinking if the quantity of dissolved minerals exceeds 1,000 milligrams per liter. Water that is pumped or released from a confined aquifer will rise to a level called the piezomatic surface, which is dictated by the pressure. When pressure forces flowing water to the surface, it is called an artesian well. The largest of these formations is Australia’s Great Artesian Basin.

Appalachian Mountains

THE APPALACHIAN Mountains of eastern North America comprise a north to south-tending range that extends for 1,600 mi (2,500 km) from the Gaspé Peninsula in Atlantic Maritime CANADA to northern ALABAMA in the UNITED STATES. Uplifted by the collision of continents ancestral to North America and Africa 270 million years ago, the Appalachian Mountains are the oldest mountain range in North America.

The Appalachian Mountains consist of a range of landforms from four physiographic provinces. The New England Province consists of rolling coastal lowlands and rugged interior highlands—like the White Mountains of NEW HAMPSHIRE and MAINE and the Green Mountains of VERMONT—of northern New England and Canada. The Ridge and Valley Province consists of long linear ridges separated by valleys with trellis drainage patterns. The valleys are rich in limestone that dissolves to produce sinkholes and underground caverns, producing KARST topography. The Ridge and Valley Province extends from NEW YORK to Alabama. The Blue Ridge Mountain Province extends from south-central PENNSYLVANIA to northern GEORGIA and is a rugged region of high relief with terrain that ranges from narrow ridges with steep slopes to broad mountains. The Appalachian Plateau (known as the Allegheny Plateau in the north and the Cumberland Plateau in the south) is a well-dissected plateau landscape with deeply eroded, dendritic drainage patterns. The Appalachian Plateau extends from New York to KENTUCKY. The northern Appalachian region from Canada to portions of northern Pennsylvania and NEW JERSEY was glaciated until 10,000 years B.C.E.

Antipode

DURING THE TIME of Plato and Aristotle (circa 390 B.C.E.), the term antipode was used in reference to a natural balance thought to be sustained by the existence of a continent south of the equator, equal in size to the northern continent. Ptolemy (100–170 C.E.) described this southern landmass as Terra Australis Incognita (unknown southern lands).

In contemporary use, the term describes a point on the opposite side of Earth from another location. Antipodes are most often expressed as latitude/longitude coordinates. It is possible to compute the antipode for a given location by subtracting 180 from the location’s longitude and changing latitude from degrees north to degrees south or vice versa. For example, the geographic center of TAIWAN is located at 121 degrees east longitude and 24 degrees north latitude. By subtracting 180 from 121 for a longitude of 59 degrees south and changing 24 degrees north to 24 degrees south, the antipode of Taiwan can be identified as being within the country of PARAGUAY in South America. Measured in great circle distance, antipodes are the farthest place on the world’s surface from each other. A true circumnavigation of the world requires a traveler to pass through at least two points that are antipodean to each other.

Some examples of true (antipodal) circumnavigations include Ferdinand MAGELLAN’s 1522 expedition in his ship Victoria and Sir Francis Drake’s 1580 journey in the Golden Hind.

Antigua and Barbuda

ANTIGUA WAS ONE of the primary British colonies in the CARIBBEAN SEA and remains a leader among the Leeward Islands (from the Virgin Islands to GUADELOUPE). Along with the nearby island of Barbuda, and the much smaller island of Redonda, Antigua became independent in 1981 but retains close links with the UNITED KINGDOM (UK) and its commonwealth.

The islands are located in the northern part of the Lesser Antilles chain, approximately 80 km (50 mi) east of SAINT KITTS AND NEVIS, and the same distance north of the French island Guadeloupe. Unlike these neighbors, none of the three main islands are volcanic and mountainous but are low-lying coral and limestone formations. Antigua was one of the first islands encountered in the voyages of Christopher Columbus, who named it Santa María de la Antigua. The Spanish and French attempted to set up colonies but were discouraged by lack of fresh water and attacks by native Carib peoples. English planters established a permanent settlement in the 1630s and within a few decades had completely deforested the island, eradicated any native population, and repopulated it with large numbers of African slaves. The chief city, St. John’s, was one of the region’s most prosperous ports in the 18th century as a center for the sugar trade but declined after the abolition of slavery in 1834. Nelson’s Dockyard, on the south side of the island, remains a testament to this prosperity and has been a national park since the 1980s. Sugar remained the island’s major product until the 1960s but has now mostly disappeared.

Barbuda, 30 mi (48 km) to the north, was never developed as a commercial sugar producer, and it retains a separate identity from its larger, more populous partner, occasionally even voicing a desire for autonomy or independence from Antigua. Most of its 1,500 residents live in the only settlement, Codrington, named for Antigua’s first major planter, who leased Barbuda to raise provisions and conduct slave-breeding experiments. Barbuda is also known among scuba divers and tourists for its numerous sunken ships and untouched reefs.

The tiny volcanic rock of Redonda, only .5 square mi (.8 square km), is located 35 mi (56 km) to the

southwest of Antigua. It is populated only by goats, seabirds, and lizards but is the seat of the fabulous “Kingdom of Redonda,” a literary-review group (mostly based in LONDON, England) established in the early 20th century.