Figure 8. Topography and Drainage
The main characteristic of Bulgaria's topography is alternating bands of high and low terrain that extend east to west across the country (see fig. 8). 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.
Data as of June 1992