The structure of the islands is basaltic rock with a thin layer of tillite (moraines) and turf.  They are rather high rising, and in some places precipitous.  The highest point is Mt. Slaettara Peak on Island Austurey.  The coastline is indented with bays and coves.  The ocean currents in the narrow sounds between the islands are very strong, when the tides and coming in and going out.