CAT

Cat, small, mainly carnivorous animal, Felis catus, member of the family Felidae, popular as a household pet, and valuable for killing mice and rats. Like other members of the cat family, the domestic cat has retractile claws; keen hearing and smell; remarkable night vision; and a compact, muscular, and highly supple body. Cats possess excellent memory and exhibit considerable aptitude for learning by observation and experience. The natural life span of a domestic cat is about 15 years.

HIMALAYAS

Himalayas, also Himalaya (Sanskrit for “abode of snow”), mountain system in Asia, forming a broad continuous arc for nearly 2,600 km (1,600 mi) along the northern fringes of the Indian subcontinent, from the bend of the Indus River in the northwest to the Brahmaputra River in the east. The Himalayas range, averaging 320 to 400 km (200 to 250 mi) in width, rises sharply from the Gangetic Plain. North of this mountain belt lies the Tibetan Plateau (Qing Zang Gaoyuan). The Himalayas form the earth’s highest mountain region, containing 9 of the 10 highest peaks in the world. Among these peaks are the world’s highest mountain, Mount Everest (8,850 m/29,035 ft), which is on the Nepal-Tibet border; the second highest peak, K2 or Mount Godwin Austen (8,611 m/28,251 ft), located on the border between China and Jammu and Kashmīr, a territory claimed by India and Pakistan; the third highest peak, Kānchenjunga (8,598 m/28,209 ft) on the Nepal-India border; Makālu (8,481 m/27,824 ft) on the Nepal-Tibet border; Dhaulāgiri (8,172 m/26,811 ft) and Annapūrna 1 (8,091 m/26,545 ft) in Nepal; Nanga Parbat (8,125 m/26,657 ft) in the Pakistani-controlled portion of Jammu and Kashmīr; and Nanda Devi (7817 m/25,645 ft) in India.

GEOLOGIC FORMATION AND STRUCTURE

The Himalayan mountain system developed in a series of stages 30 to 50 million years ago. The Himalayan range was created from powerful earth movements that occurred as the Indian plate pressed against the Eurasian continental plate (see Plate Tectonics). The earth movements raised the deposits laid down in the ancient, shallow Tethys Sea (on the present site of the mountains) to form the Himalayan ranges from Pakistan eastward across northern India, and from Nepal and Bhutan to the Myanmar (Burmese) border. Even today the mountains continue to develop and change, and earthquakes and tremors are frequent in the area.

TOPOGRAPHY

Physically, the Himalayas forms three parallel zones: the Great Himalayas, the Middle Himalayas (also known as the Inner or Lesser Himalayas), and the Sub-Himalayas, which includes the Siwālik Range and foothills and the Tarāi and Duars piedmont (an area of land formed or lying at the foot of a mountain or mountain range). Each of these lateral divisions exhibit certain similar topographic features. The Great Himalayas, the highest zone, consists of a huge line of snowy peaks with an average height exceeding 6,100 m (20,000 ft). The width of this zone, composed largely but not entirely of gneiss and granite, is about 24 km (about 15 mi). Spurs from the Great Himalayas project southwards into the Middle Himalayas in an irregular fashion. The Nepal and Sikkim (a state of northern India) portion of the Great Himalayas contains the greatest number of high peaks. The snow line on the southern slopes of the Great Himalayas varies from 4,480 m (14,700 ft) in the eastern and central Himalayas of Nepal and Sikkim to 5,180 m (17,000 ft) in the western Himalayas. To the north of the Great Himalayas are several ranges such as the Zāskār, Ladakh, and the Kailas. The Karakoram Range lies on the Tibetan side of the Great Himalayas.

The Great Himalayan region is one of the few remaining isolated and inaccessible areas in the world today. Some high valleys in the Great Himalayas are occupied by small clustered settlements. Extremely cold winters and a short growing season limit the farmers to one crop per year, most commonly potatoes or barley. The formidable mountains have limited the development of large-scale trade and commerce despite the construction of highways across the mountains linking Nepal and Pakistan to China. Older trails, which cross the mountains at high passes, also have limited trade and are open only during the summer months.
The Middle Himalayas range, which has a width of about 80 km (about 50 mi), borders the Great Himalayan range on the south. It consists principally of high ranges both within and outside of the Great Himalayan range. Some of the ranges of the Middle Himalayas are the Nāg Tibba, the Dhaola Dhār, the Pīr Panjāl, and the Mahābhārat. The Middle Himalayas possess a remarkable uniformity of height; most are between 1,830 and 3,050 m (between 6000 and 10,000 ft).
The Middle Himalayas region is a complex mosaic of forest-covered ranges and fertile valleys. While not as forbidding as the Great Himalayas to the north, this range has nonetheless served to isolate the valleys of the Himalayas from the plains of the Indus and Ganges rivers in Pakistan and northern India. Except for the major valley centers such as Srīnagar, Kāngra, and Kathmandu, and hill towns such as Simla, Mussoorie, and Dārjiling (Darjeeling), the region is moderately populated. Within the Middle Himalayas the intervening mountain ranges tend to separate the densely populated valleys. The numerous gorges and rugged mountains make surface travel difficult in any direction. Few roads or transport routes exist between towns, partly because it is expensive to build them over the high, rough terrain. Only major population centers are linked by air and roads with principal cities in India and Pakistan.
The Sub-Himalayas, which is the southernmost and the lowest zone, borders the plains of North India and Pakistan. It comprises the Siwālik Range and foothills as well as the narrow piedmont plain at the base of the mountains. The width of the Sub-Himalayas gradually narrows from about 48 km (about 30 mi) in the west until it nearly disappears in Bhutan and eastern India. A characteristic feature of the Sub-Himalayas is the large number of long, flat-bottomed valleys known as duns, which are usually spindle-shaped and filled with gravelly alluvium. South of the foothills lies the Tarāi and Duars plains. The southern part of the Tarāi and Duars plains is heavily farmed. The northern part was forest inhabited by wild animals until about the 1950s. Most of the forests of this region have been destroyed, and much of the land has been reclaimed for agriculture.

The Great Himalayan region is one of the few remaining isolated and inaccessible areas in the world today. Some high valleys in the Great Himalayas are occupied by small clustered settlements. Extremely cold winters and a short growing season limit the farmers to one crop per year, most commonly potatoes or barley. The formidable mountains have limited the development of large-scale trade and commerce despite the construction of highways across the mountains linking Nepal and Pakistan to China. Older trails, which cross the mountains at high passes, also have limited trade and are open only during the summer months.
The Middle Himalayas range, which has a width of about 80 km (about 50 mi), borders the Great Himalayan range on the south. It consists principally of high ranges both within and outside of the Great Himalayan range. Some of the ranges of the Middle Himalayas are the Nāg Tibba, the Dhaola Dhār, the Pīr Panjāl, and the Mahābhārat. The Middle Himalayas possess a remarkable uniformity of height; most are between 1,830 and 3,050 m (between 6000 and 10,000 ft).
The Middle Himalayas region is a complex mosaic of forest-covered ranges and fertile valleys. While not as forbidding as the Great Himalayas to the north, this range has nonetheless served to isolate the valleys of the Himalayas from the plains of the Indus and Ganges rivers in Pakistan and northern India. Except for the major valley centers such as Srīnagar, Kāngra, and Kathmandu, and hill towns such as Simla, Mussoorie, and Dārjiling (Darjeeling), the region is moderately populated. Within the Middle Himalayas the intervening mountain ranges tend to separate the densely populated valleys. The numerous gorges and rugged mountains make surface travel difficult in any direction. Few roads or transport routes exist between towns, partly because it is expensive to build them over the high, rough terrain. Only major population centers are linked by air and roads with principal cities in India and Pakistan.
The Sub-Himalayas, which is the southernmost and the lowest zone, borders the plains of North India and Pakistan. It comprises the Siwālik Range and foothills as well as the narrow piedmont plain at the base of the mountains. The width of the Sub-Himalayas gradually narrows from about 48 km (about 30 mi) in the west until it nearly disappears in Bhutan and eastern India. A characteristic feature of the Sub-Himalayas is the large number of long, flat-bottomed valleys known as duns, which are usually spindle-shaped and filled with gravelly alluvium. South of the foothills lies the Tarāi and Duars plains. The southern part of the Tarāi and Duars plains is heavily farmed. The northern part was forest inhabited by wild animals until about the 1950s. Most of the forests of this region have been destroyed, and much of the land has been reclaimed for agriculture.

CLIMATE
The Himalayas influences the climate of the Indian subcontinent by sheltering it from the cold air mass of Central Asia. The range also exerts a major influence on monsoon and rainfall patterns. Within the Himalayas climate varies depending on elevation and location. Climate ranges from subtropical in the southern foothills, with average summer temperatures of about 30° C (about 86° F) and average winter temperatures of about 18° C (about 64° F); warm temperate conditions in the Middle Himalayan valleys, with average summer temperatures of about 25° C (about 77° F) and cooler winters; cool temperate conditions in the higher parts of the Middle Himalayas, where average summer temperatures are 15 to 18° C (59 to 64° F) and winters are below freezing; to a cold alpine climate at higher elevations, where summers are cool and winters are severe. At elevations above 4,880 m (16,000 ft) the climate is very cold with below freezing temperatures and the area is permanently covered with snow and ice. The eastern part of the Himalayas receives heavy rainfall; the western part is drier.

MOUNTAIN

Mountain, name usually applied to region of land that is raised rather steeply above the surrounding terrain. Mountains are distinguishable from plateaus by mountains’ usually limited summit area (mountains are generally much narrower at the top than at the base) and they are distinguishable from hills by mountains’ generally higher elevation. The elevation, or altitude, of a mountain is given as the height of the summit above sea level. Therefore, a mountain with an elevation of 4000 m (13,100 ft) may rise to a level of only 3000 m (9840 ft) above the surrounding land.

Mountains are normally found in groups or ranges consisting of peaks, ridges, and intermontane (between mountains) valleys. Except for certain mountains that occur singly, the smallest unit pertaining to mountains is the range, comprising either a single complex ridge or a series of ridges generally alike in origin, age, and form. Several closely related ranges in a parallel alignment or chainlike cluster are known as a mountain system; an elongated series of systems forms a mountain chain; and an extensive complex of ranges, systems, and chains is known as a belt, or cordillera

FORMATION

Geologists believe that most mountains are formed by movements in the earth’s crust. The plate tectonics model has helped explain many of these processes. This model describes the crust of the earth as made up of a number of vast plates that move about at the rate of a few centimeters a year leading to the collision and separation of continents and the subsequent development of mountain belts.
Movements that result in collisions between plates tend to raise the crust by faulting, folding, or arching up layers of rock. Movements that result in separation, or rifting, of plates cause some blocks of crust to sink, leaving other blocks to tower above them. Volcanic eruptions also raise mountains, and much of the world’s volcanic activity is concentrated along the active margins of crustal plates. Finally, some ranges of low mountains are created by nontectonic processes, chief among these being the sculpturing effects of erosion, which wears away softer rock and leaves the harder rock.

A Uplift

Collisions between plates of the earth’s crust trigger various geologic processes that result in crustal uplift. A common process, produced by horizontal compression, is the deformation of crustal strata into folds or wrinkles (see Geomorphology) or the thrusting of vast, thick sheets of rock over one another (see Fault). The Himalayas, for example, were raised by the compression that accompanied collision of the Indian plate with the Eurasian one. Europe’s Alps and Jura Mountains also formed because of horizontal compression, generated in their case by collision of the African plate with the Eurasian one. Similarly, the Appalachian Mountains rose in response to forces caused by repeated collisions between the North American plate and the African and European ones, and most of the Rocky Mountains rose because of the compressive effects generated by collisions between the North American and Pacific plates.
Formation of a basin-and-range structure, best exemplified by the basin-and-range areas in Nevada and Utah (see Great Basin), is the result of movement of rock along faults, or major deep cracks, in the crust of the earth. Occasionally, such movement, called faulting, causes rock bordering on faults to be lifted vertically in great blocks. The raised edges of the blocks then appear as mountains, the depressed edges as valleys. Such mountains are also widely known as fault-block mountains.
A third type of mountain formed by uplifting is called the dome. The dome structure is typified by the Henry and Abajo Mountains in Utah, and by the Adirondack Mountains in New York. These mountains are created by deep-seated intrusion of igneous, or molten, rock that arches the rocks at the surface.

B Erosion

Rock on the surface of the earth is constantly exposed to erosion. Because rocks of different composition resist erosion differently, areas of relatively hard rock may stand high above areas of softer, more easily eroded rock. Mountains resulting from this erosive sculpturing of the land may be linear in appearance if the resistant rock is the upturned edge of a sedimentary rock unit, flat-topped buttes or mesas if the harder rock is a flat-lying unit, or complex and irregular ranges if the resistant rocks are an uncovered intrusive igneous mass. Portions of the Ozark Plateau (also known as the Ozark Mountains) in Arkansas and Missouri are good examples of mountains created by the forces of erosion.

C Volcanism

Mountains formed by volcanic action are well known because of their usually isolated occurrence and periodically dangerous aspect. Most spectacular and probably most familiar are the conical peaks composed of lava and volcanic debris, such as Mount Rainier and Mount Saint Helens in the western United States, Mount Erebus in Antarctica, Mount Vesuvius in Italy, and Fuji in Japan. Many of these volcanic mountains have summit craters that still emit steam and debris; others no longer showing signs of volcanic activity may be only dormant, not extinct. Shield volcanoes, typified by Mauna Loa and Mauna Kea in Hawaii, are less spectacular even when quite high, since the physical properties of their formative material have shaped them into broad shieldlike masses that deemphasize their height.

IMPORTANCE

Mountains affect life in many ways. Apart from their mineral, forest, agricultural, and recreational resource value, they exert a significant influence on climate and determine the course of economic or historical trends. Especially high mountain ranges, such as the Sierra Nevada in the U.S., the Andes in South America, and the Himalayas in Asia, markedly affect climate and weather patterns over vast areas of the earth because they stand as barriers to regularly circulating air masses. Moisture carried inland by winds from the Pacific Ocean, for example, is lost in the form of rain and snow on the windward sides of the Sierra Nevada and Andes; the leeward, or inland, side is drier, and the land beyond is frequently arid.
The importance of mountains with regard to the history and economy of various nations can be shown by their influence upon the development of the western United States. The first travelers and settlers, and then the earliest railroads, avoided mountain crossings because of the dangers and costs involved. Later, however, the vast deposits of minerals that became so vitally important to the development of several western states were found exposed principally in mountainous areas, and the lure of “striking it rich” drew people and railroads west despite the hardships encountered in traversing the passes. As a result, transportation routes and patterns, with large populations centered about them, were established; most of these remain today.
The political significance of mountains has been noticeable throughout human history. Mountain barriers with their relatively narrow and easily defendable passes have made various ranges throughout the world natural political boundaries, second in strategic importance only to oceans and seas.
Most of the world’s highest mountains lie in the great Himalayan system and the cordillera stretching through North and South America. The accompanying table includes the highest mountains found on each continent.