Loch Lomond lies on the Highland Boundary Fault, the boundary between the Lowlands of Central Scotland and the Highlands. It is 24 miles (39 kilometres) long and between 0.75 mile (1.21 km) and 5 miles (8 km) wide. It has an average depth of about 121 feet (37 metres), and a maximum depth of about 620 feet (190 metres). Its surface area is 27 square miles (71 km), and it has a volume of 0.62 cubic miles (2.6 km). 