A narrow strait from the south of Loch Alsh leads to the Sound of Sleat that separates the Isle of Skye from the mainland.[3] Much of the countryside is moorland or pasture but there are lowland areas of deciduous forest with native birchwoods and oakwoods and some conifer plantations.The Lewisian gneisses around Loch Alsh were formed in the Precambrian period, about 2,800 million years ago, while the volcanic rocks, gabbro and granite that make up most of Skye, and that in some places lie under the older gneisses, are just 55 million years old.[8] The ancient metamorphic rocks around Loch Alsh have been heavily eroded over the years, most recently by a series of ice ages.[9] In 2012, a large colony of flame shells was discovered in the loch following a Marine Scotland commissioned survey, carried out by Heriot-Watt University.