page_title: Slavonia
section_title: Topography
hierarchical_section_title: Slavonia / Geography / Physical geography / Topography
caption_attribution_description: Hrvatski: sh:Orahovačko jezero, sh:Hrvatska
context_page_description: Slavonia is, with Dalmatia, Croatia proper and Istria, one of the four historical regions of Croatia. Taking up the east of the country, it roughly corresponds with five Croatian counties: Brod-Posavina, Osijek-Baranja, Požega-Slavonia, Virovitica-Podravina and Vukovar-Syrmia, although the territory of the counties includes Baranya, and the definition of the western extent of Slavonia as a region varies. The counties cover 12,556 square kilometres or 22.2% of Croatia, inhabited by 806,192—18.8% of Croatia's population. The largest city in the region is Osijek, followed by Slavonski Brod and Vinkovci.
  Slavonia is located in the Pannonian Basin, largely bordered by the Danube, Drava and Sava rivers. In the west, the region consists of the Sava and Drava valleys and the mountains surrounding the Požega Valley, and plains in the east. Slavonia enjoys a moderate continental climate with relatively low precipitation.
  After the fall of the Western Roman Empire, which ruled the area of modern-day Slavonia until the 5th century, Ostrogoths and Lombards controlled the area before the arrival of Avars and Slavs, when the Principality of Lower Pannonia was established in the 7th century.
context_section_description: Slavonia is entirely located in the Pannonian Basin, one of three major geomorphological parts of Croatia. The Pannonian Basin took shape through Miocenian thinning and subsidence of crust structures formed during Late Paleozoic Variscan orogeny. The Paleozoic and Mesozoic structures are visible in Papuk and other Slavonian mountains. The processes also led to the formation of a stratovolcanic chain in the basin 17 – 12 Mya (million years ago) and intensified subsidence observed until 5 Mya as well as flood basalts about 7.5 Mya. Contemporary uplift of the Carpathian Mountains prevented water flowing to the Black Sea, and the Pannonian Sea formed in the basin. Sediments were transported to the basin from uplifting Carpathian and Dinaric mountains, with particularly deep fluvial sediments being deposited in the Pleistocene during the uplift of the Transdanubian Mountains. Ultimately, up to 3,000 metres (9,800 feet) of the sediment was deposited in the basin, and the Pannonian sea eventually drained through the Iron Gate gorge. In the southern Pannonian Basin, the Neogene to Quaternary sediment depth is normally lower, averaging 500 to 1,500 metres (1,600 to 4,900 feet), except in central parts of depressions formed by subduction—around 4,000 metres (13,000 feet) in the Slavonia-Syrmia depression, 5,500 metres (18,000 feet) in the Sava depression and nearly 7,000 metres (23,000 feet) in the Drava depression, with the deepest sediment found between Virovitica and Slatina.
  The results of those processes are large plains in eastern Slavonia, Baranya and Syrmia, as well as in river valleys, especially along the Sava, Drava and Kupa. The plains are interspersed by the horst and graben structures, believed to have broken the Pannonian Sea surface as islands.  The tallest among such landforms in Slavonia are 984-metre (3,228 ft) Psunj, and 953-metre (3,127 ft) Papuk—flanking the Požega Valley from the west and the north. These two and Krndija, adjacent to Papuk, consist mostly of Paleozoic rocks which are 350 – 300 million years old. Požeška Gora and Dilj, to the east of Psunj and enveloping the valley from the south, consist of much more recent Neogene rocks, but Požeška Gora also contains Upper Cretaceous sediments and igneous rocks forming the main, 30-kilometre (19 mi) ridge of the hill and representing the largest igneous landform in Croatia. A smaller igneous landform is also present on Papuk, near Voćin. The two mountains, as well as Moslavačka gora, west of Pakrac, are possible remnants of a volcanic arc related to Alpine orogeny—uplifting of the Dinaric Alps. The Đakovo – Vukovar loess plain, extending eastward from Dilj and representing the watershed between the Vuka and Bosut rivers, gradually rises to the Fruška Gora south of Ilok.
caption: Orahovac Lake
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