    Physical features          Coastal features  The coasts of
Sweden and Finland are highly fretted and generally rocky,
whereas those of the southern Baltic are flat and rather
featureless. Where the crystalline rocks of the ancient rock
mass of the Baltic Shield outcrop along the northern coasts,
partly obscured by glacial drift and marine deposits, they are
often fringed by the low, rocky islands known as a skerry guard.
These are most numerous in the Saltsjön (Salt Bay) between
Stockholm and the open waters of the Gulf of Bothnia and off the
southwest coast of Finland. Off southeastern Sweden the narrow,
elongated islands of Öland and Gotland consist of ancient
limestone partly covered by sandy drift deposits. The
rectangular island of Bornholm off southern Sweden was formed
from a detached fragment of granite, and its high cliffs were
shaped by faulting and shearing of the rock strata.  The coastal
features of eastern Denmark are the outcome of Pleistocene
glaciation and of subsequent changes in sea lev