Formation of Scotland

c.450 million BC - Grampian Mountains and the northern Highlands formed by geological sheets which slide along lines of weakness where they collide and fuse together:

• The Highland Boundary Fault is a giant fracture in the earth's crust stretches across Scotland from the Firth of Clyde, in the southwest, to Stonehaven, in the northeast, separating the lowlands to the south from the highlands to the north.
• The Great Glen Fault runs northwest through the Great Glen.

About four hundred million years ago in the Glen Coe area, molten rock rose from deep in the earth's crust causing the metamorphic rock cover to form a dome. As the upward pressure became stronger rock around part of the dome cracked allowing lava to flow out. Eruptions emptied the magma layer beneath the dome causing it to collapse forming a pit, or caldera, about five miles wide. Clouds of ash formed the rock ignimbrite. Further lava flows filled the pit with saucer shaped layers and this sequence was later repeated. Molten rock continued to penetrate upwards into the fault, later hardening to form a feature known as a ring dyke.

c.200 million BC - A shift in the earth's crust forms the Great Glen itself.

c.18,000 BC - Glaciers create the four main lochs (Linnhe, Lochy, Oich and Ness) along the Great Glen.

• Lewisian - metamorphic and igneous rock found in the Outer Hebrides and west coast dating back 3300 million years - the oldest in the British Isles.

• Dalradian - belt of metamorphic rock in the southern Grampians.

c.10,000 BC - As the ice melts following the last Ice Age, animals spread north.

c.7,000 BC - The first inhabitants arrive in Scotland.

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