摘要：The Middle Struma complex morphostructural passage (N 42°14'62''-41°21'19''; E 24°10'21''-23°20'21'') is a negative landform located in South-West Bulgaria. Represents a negative regional morphounit composed of linear orderly (from north to the south) Dupnitsa morphostructural threshold, Dzherman morphostructural passage, Slatino morphostructural threshold, Mursalevo morphostructural passage, Kocherinovo morphostructural threshold, Riltsi kettle morphostructure, Byalo Pole morphostructural threshold, Blagoevgrad kettle morphostructure, Zheleznitsa morphostructural gorge, Simitli kettle morphostructure, Kresna morphostructural gorge, Sandanski morphostructural passage, Damyanitsa morphostructural threshold, Petrich kettle morphostructure and Rupel morphostructural gorge. The mentioned regional complex morphounits are limited by Bregalnitsa morphostructural zone to the west and the Rila-Pirin morphostrutural range to the east. The Middle Struma complex morphostructural passage is the relict from the post Early Pleistocene orthoplain in the eastern part of the Balkan Peninsula. The internal morphostructures of that orthoplain fragment were formed in the same time with the building of the dome-like morphostructures of the Bregalnitsa morphostructural zone and the Rila-Pirin morphostrutural range.
