The land area of Bulgaria is 110,550 square kilometers, slightly larger than that of the state of Tennessee. The country is situated on the west coast of the Black Sea, with Romania to the north, Greece and Turkey to the south, and Yugoslavia to the west. Considering its small size, Bulgaria has a great variety of topographical features. Even within small parts of the country, the land may be divided into plains, plateaus, hills, mountains, basins, gorges, and deep river valleys.
Although external historical events often changed Bulgaria's national boundaries in its first century of existence, natural terrain features defined most boundaries after 1944, and no significant group of people suffered serious economic hardship because of border delineation. Postwar Bulgaria contained a large percentage of the ethnic Bulgarian people, although numerous migrations into and out of Bulgaria occurred at various times. None of the country's borders was officially disputed in 1991, although nationalist Bulgarians continued to claim that Bulgaria's share of Macedonia--which it shared with both Yugoslavia and Greece--was less than just because of the ethnic connection between Macedonians and Bulgarians.
In 1991 Bulgaria had a total border of about 2,264 kilometers. Rivers accounted for about 680 kilometers and the Black Sea coast for 400 kilometers; the southern and western borders were mainly defined by ridges in high terrain. The western and northern boundaries were shared with Yugoslavia and Romania, respectively, and the Black Sea coastline constituted the entire eastern border. The Romanian border followed the Danube River for 464 kilometers from the northwestern corner of the country to the city of Silistra and then cut to the east-southeast for 136 kilometers across the northeastern province of Varna. The Danube, with steep bluffs on the Bulgarian side and a wide area of swamps and marshes on the Romanian side, was one of the most effective river boundaries in Europe. The line through Dobruja was arbitrary and was redrawn several times according to international treaties. In that process, most inhabitants with strong national preferences resettled in the country of their choice. Borders to the south were with Greece and Turkey. The border with Greece was 491 kilometers long, and the Turkish border was 240 kilometers long.
The main characteristic of Bulgaria's topography is alternating bands of high and low terrain that extend east to west across the country. From north to south, those bands are the Danubian Plateau, the Balkan Mountains (called Stara Planina, meaning old mountains in Bulgarian), the central Thracian Plain, and the Rhodope Mountains. The easternmost sections near the Black Sea are hilly, but they gradually gain height to the west until the westernmost part of the country is entirely high ground.
More than two-thirds of the country is plains, plateaus, or hilly land at an altitude less than 600 meters. Plains (below 200 meters) make up 31 percent of the land, plateaus and hills (200 to 600 meters) 41 percent, low mountains (600 to 1,000 meters) 10 percent, medium-sized mountains (1,000 to 1,500 meters) 10 percent, and high mountains (over 1,500 meters) 3 percent. The average altitude in Bulgaria is 470 meters.
The Danubian Plateau extends from the Yugoslav border to the Black Sea. It encompasses the area between the Danube River, which forms most of the country's northern border, and the Balkan Mountains to the south. The plateau slopes gently from cliffs along the river, then it abuts mountains of 750 to 950 meters. The plateau, a fertile area with undulating hills, is the granary of the country.
The southern edge of the Danubian Plateau blends into the foothills of the Balkan Mountains, the Bulgarian part of the Carpathian Mountains. The Carpathians resemble a reversed S as they run eastward from Czechoslovakia across the northern portion of Romania, swinging southward to the middle of Romania and then running westward, where they are known as the Transylvanian Alps. The mountains turn eastward again at the Iron Gate, a gorge of the Danube River at the Romanian-Yugoslav border. At that point, they become the Balkan Mountains of Bulgaria.
The Balkan Mountains originate at the Timok Valley in Yugoslavia and run southward towards the Sofia Basin in west central Bulgaria. From there they run east to the Black Sea. The Balkans are about 600 kilometers long and 30 to 50 kilometers wide. They retain their height well into central Bulgaria, where Botev Peak, the highest point in the Balkan Mountains, rises to about 2,376 meters. The range then continues at lower altitude to the cliffs of the Black Sea. Through most of Bulgaria, the Balkans form the watershed from which rivers drain north to the Danube River or south to the Aegean Sea. Some smaller rivers in the east drain directly to the Black Sea. The Sredna Gora (central hills) is a narrow ridge about 160 kilometers long and 1,600 meters high, running east to west parallel to the Balkans. Just to the south is the Valley of Roses, famous for rose oil used in perfume and liqueurs.
The southern slopes of the Balkan Mountains and the Sredna Gora give way to the Thracian Plain. Roughly triangular in shape, the plain originates at a point east of the mountains near Sofia and broadens eastward to the Black Sea. It includes the Maritsa River valley and the lowlands that extend from the river to the Black Sea. Like the Danubian Plateau, much of the Thracian Plain is somewhat hilly and not a true plain. Most of its terrain is moderate enough to cultivate.
The Rhodope Mountains occupy the area between the Thracian Plain and the Greek border to the south. The western Rhodopes consist of two ranges: the Rila Mountains south of Sofia and the Pirin Mountains in the southwestern corner of the country. They are the most outstanding topographic feature of Bulgaria and of the entire Balkan Peninsula. The Rila range includes Mount Musala, whose 2,975-meter peak is the highest in any Balkan country. About a dozen other peaks in the Rilas are over 2,600 meters. The highest peaks are characterized by sparse bare rocks and remote lakes above the tree line. The lower peaks, however, are covered with alpine meadows that give the range an overall impression of green beauty. The Pirin range is characterized by rocky peaks and stony slopes. Its highest peak is Mount Vikhren, at 2,915 meters the secondhighest peak in Bulgaria.
The largest basin in Bulgaria is the Sofia Basin. About twentyfour kilometers wide and ninety-six kilometers long, the basin contains the capital city and the area immediately surrounding it. The route through basins and valleys from Belgrade to Istanbul (formerly Constantinople) via Sofia has been historically important since Roman times, determining the strategic significance of the Balkan Peninsula. Bulgaria's largest cities were founded on this route. Paradoxically, although the mountains made many Bulgarian villages and towns relatively inaccessible, Bulgaria has always been susceptible to invasion because no natural obstacle blocked the route through Sofia.
A significant part of Bulgaria's land is prone to earthquakes. Two especially sensitive areas are the borders of the North Bulgarian Swell (rounded elevation), the center of which is in the Gorna Oryakhovitsa area in north-central Bulgaria, and the West Rhodopes Vault, a wide area extending through the Rila and northern Pirin regions to Plovdiv in south-central Bulgaria. Especially strong tremors also occur along diagonal lines running between Skopje in the Republic of Macedonia and Razgrad in northeast Bulgaria, and from Albania eastward across the southern third of Bulgaria through Plovdiv. Sixteen major earthquakes struck Bulgaria between 1900 and 1986, the last two in Strazhitsa on the SkopjeRazgrad fault line. Together the two quakes damaged over 16,000 buildings, half of them severely. One village was almost completely leveled, others badly damaged. Many inhabitants were still living in temporary housing four years later.
The Balkan Mountains divide Bulgaria into two nearly equal drainage systems. The larger system drains northward to the Black Sea, mainly by way of the Danube River. This system includes the entire Danubian Plateau and a stretch of land running forty-eight to eighty kilometers inland from the coastline. The second system drains the Thracian Plain and most of the higher lands of the south and southwest to the Aegean Sea. Although only the Danube is navigable, many of the other rivers and streams in Bulgaria have a high potential for the production of hydroelectric power and are sources of irrigation water.
Of the Danube's Bulgarian tributaries, all but the Iskur rise in the Balkan Mountains. The Iskur flows northward to the Danube from its origin in the Rila Mountains, passing through Sofia's eastern suburbs and through a Balkan Mountain valley.
The Danube gets slightly more than 4 percent of its total volume from its Bulgarian tributaries. As it flows along the northern border, the Danube averages 1.6 to 2.4 kilometers in width. The river's highest water levels usually occur during June floods; it is frozen over an average of forty days per year.
Several major rivers flow directly to the Aegean Sea. Most of these streams fall swiftly from the mountains and have cut deep, scenic gorges. The Maritsa with its tributaries is by far the largest draining all of the western Thracian Plain, all of the Sredna Gora, the southern slopes of the Balkan Mountains, and the northern slopes of the eastern Rhodopes. After it leaves Bulgaria, the Maritsa forms most of the Greek-Turkish border. The Struma and the Mesta (which separate the Pirin Mountains from the main Rhodopes ranges) are the next largest Bulgarian rivers flowing to the Aegean. The Struma and Mesta reach the sea through Greece.
Considering its small area, Bulgaria has an unusually variable and complex climate. The country lies between the strongly contrasting continental and Mediterranean climatic zones. Bulgarian mountains and valleys act as barriers or channels for air masses, causing sharp contrasts in weather over relatively short distances. The continental zone is slightly larger, because continental air masses flow easily into the unobstructed Danubian Plain. The continental influence, stronger during the winter, produces abundant snowfall; the Mediterranean influence increases during the summer and produces hot, dry weather. The barrier effect of the Balkan Mountains is felt throughout the country: on the average, northern Bulgaria is about one degree cooler and receives about 192 more millimeters of rain than southern Bulgaria. Because the Black Sea is too small to be a primary influence over much of the country's weather, it only affects the immediate area along its coastline.
The Balkan Mountains are the southern boundary of the area in which continental air masses circulate freely. The Rhodope Mountains mark the northern limits of domination by Mediterranean weather systems. The area between, which includes the Thracian Plain, is influenced by a combination of the two systems, with the continental predominating. This combination produces a plains climate resembling that of the Corn Belt in the United States, with long summers and high humidity. The climate in this region is generally more severe than that of other parts of Europe in the same latitude. Because it is a transitional area, average temperatures and precipitation are erratic and may vary widely from year to year.
Average precipitation in Bulgaria is about 630 millimeters per year. Dobruja in the northeast, the Black Sea coastal area, and parts of the Thracian Plain usually receive less than 500 millimeters. The remainder of the Thracian Plain and the Danubian Plateau get less than the country average; the Thracian Plain is often subject to summer droughts. Higher elevations, which receive the most rainfall in the country, may average over 2,540 millimeters per year.
The many valley basins scattered through the uplands have temperature inversions resulting in stagnant air. Sofia is located in such a basin, but its elevation (about 530 meters) tends to moderate summer temperature and relieve oppressive high humidity. Sofia also is sheltered from the northern European winds by the mountains that surround its troughlike basin. Temperatures in Sofia average -2°C in January and about 21°C in August. The city's rainfall is near the country average, and the overall climate is pleasant.
The coastal climate is moderated by the Black Sea, but strong winds and violent local storms are frequent during the winter. Winters along the Danube River are bitterly cold, while sheltered valleys opening to the south along the Greek and Turkish borders may be as mild as areas along the Mediterranean or Aegean coasts.
Like the other European members of the Council for Mutual Economic Assistance (Comecon), Bulgaria saw unimpeded industrial growth as a vital sign of social welfare and progress toward the socialist ideal. Because this approach made environmental issues a taboo subject in socialist Bulgaria, the degree of damage by postwar industrial policy went unassessed until the government of Todor Zhivkov (1962-89) was overthrown in late 1989. The Zhivkov government's commitment to heavy industry and lack of money to spend on protective measures forced it to conceal major environmental hazards, especially when relations with other countries were at stake. Factories that did not meet environmental standards paid symbolic fines and had no incentive to institute real environmental protection measures. Even as late as 1990, socialist officials downplayed the effects on Bulgaria of radiation from the 1986 nuclear power plant accident at Chernobyl'. Citizens were informed that they need not take iodine tablets or use any other protective measures.
In 1991 Bulgarian environmentalists estimated that 60 percent of the country's agricultural land was damaged by excessive use of pesticides and fertilizers and by industrial fallout. In 1991 twothirds of Bulgarian rivers were polluted, and the Yantra River was classified as the dirtiest river in Europe. By that time, about two-thirds of the primary forests had been cut. However, despite its recognition of the need for greater environmental protection, Bulgaria budgeted only 10.4 billion leva to remedy ecological problems in 1991.
Perhaps the most serious environmental problem in Bulgaria was in the Danube port city of Ruse. From 1981 to 1989, the chemical pollution that spread from a chlorine and sodium plant across the Danube in Giurgiu, Romania, was a forbidden subject in Bulgaria because it posed a threat to good relations between two Warsaw Pact countries. Chemical plants in Ruse also contributed to the pollution. Citizen environmentalists opposing the situation in Ruse organized the first demonstrations and the first independent political group to oppose the Zhivkov regime. During the Giurgiu plant's first year of operation, chlorine levels in Ruse almost doubled, reaching two times the permissible maximum in the summer of 1990. Over 3,000 families left the city in the 1980s despite government restrictions aimed at covering up the problem. Besides chlorine and its byproducts , the plant produced chemical agents for the rubber industry, and in 1991 some sources reported that the plant was processing industrial waste from Western countries--both activities likely to further damage Ruse's environment. International experts claimed that half of Ruse's pollutants came from Giurgiu, and the others came from Bulgarian industries. In response to the formidable Bulgarian environmental movement, some Bulgarian plants have been closed or have added protective measures; the Giurgiu plant, however, was planning to expand in 1991.
Pollution of agricultural land from a copper plant near the town of Srednogorie provoked harsh public criticism. The plant emitted toxic clouds containing copper, lead, and arsenic. In 1988 it released toxic wastewater into nearby rivers used to irrigate land in the Plovdiv-Pazardzhik Plain, which includes some of Bulgaria's best agricultural land. The groundwater beneath the plain also was poisoned. Work has begun on a plan to drain toxic wastewater from the plant's reservoir into the Maritsa River. Environmental improvements for the copper plant and three other factories in the Plovdiv area (a lead and zinc factory, a chemical factory, and a uranium factory) also were planned, but they would take years to implement.
None of Bulgaria's large cities escaped serious environmental pollution. Statistics showed that 70 to 80 percent of Sofia's air pollution is caused by emissions from cars, trucks, and buses. Temperature inversions over the city aggravated the problem. Two other major polluters, the Kremikovtsi Metallurgy Works and the Bukhovo uranium mine (both in southwestern Bulgaria), contaminated the region with lead, sulfur dioxide, hydrogen sulfide, ethanol, and mercury. The city of Kurdzhali became heavily polluted with lead from its lead and zinc complex. In 1973 the petroleum and chemical plant near the Black Sea port of Burgas released large amounts of chlorine in an incident similar to the one in Srednogorie. Environmentalists estimated that the area within a thirty-kilometer radius of the plant was rendered uninhabitable by that release. The air in Burgas was also heavily polluted with carbon and sulfur dioxide in 1990.
In 1990 environmental scientists claimed that two-thirds of Bulgaria's population suffered from the polluted environment to some degree. In 1991 Bulgaria began seeking international assistance in solving environmental problems. Besides joining Romania, Turkey, and the Soviet Union in joint scientific studies of the critically polluted Black Sea, Bulgaria actively sought environmental technology and expertise from Western Europe and the United States.
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