Many of the spurs or broken segments of ranges thus formed abut steeply upon the Black Sea, so that this littoral region is on the whole very rugged and not readily accessible, especially as the general elevations are considerable.
In the north-western section the highest ground is found along the Atlantic coast, mounting steeply from the sea to an average height of 2000 to 3000 ft.
The mountains generally fall steeply to the sea.
North of Bhutan, between the Himalayan crest and Lhasa, this formation is approximately maintained; farther east, although the same natural forces first resulted in the same effect of successive folds of the earth's crust, forming extensive curves of ridge and furrow, the abundant rainfall and the totally distinct climatic conditions which govern the processes of denudation subsequently led to the erosion of deeper valleys enclosed between forest-covered ranges which rise steeply from the river banks.
The sides of this ridge run down steeply to the water on either side.