In the balkans, this physical characteristic has served to separate ethnic groups. fjords mountains swamps tundra

mountains

Explanation:

The Balkan peninsula or the Balkan peninsula is one of the three great peninsulas of southeastern Europe, continent to which is united by the Balkan mountains to the east (mountain ranges that have given name to the peninsula) and the Dinaric Alps, to the west.

It is surrounded by seas on three sides: the Adriatic and the Ionian, to the west; the Aegean, to the south; and the Marmara and the Negro to the east. To the north, the peninsula is generally delimited by the course of the Danube rivers - the main one in the area -, 1 Sava and Kupa. It is separated from Asia by the straits of Dardanelles and the Bosphorus. To the west, the Dinaric Alps separate the interior of the Adriatic Sea. In the south, several rivers -among them the Vardar and the Struma- that flow into the Aegean facilitate access to the peninsular center.1 The main north-south communication route is made up of the Morava and Vardar rivers, which together cross almost all the peninsula.

A mountain range of about 650 masl crosses this peninsula, separating Bulgaria from Romania, between the basins of the Danube, the Marmara, the archipelago of the Sporades Islands and the Dardanelles, which corresponds to the mountain of Yumkusal (2380 m).

The southern slope is much steeper than the northern slope. Coniferous and deciduous forests. The Iskar Valley and the ports of Sipka and Trojan are the most important steps. With the toponym Hemo, the mountain mass of the Balkans was referred to in antiquity in Bulgaria, which extends from west to east from Serbia to the Black Sea.

the answer is richard nixion