The break-up of Gondwana

Around 180 m.y. ago (Jurassic) the supercontinent of Gondwana began to break up, heralded by intrusion and extrusion of basic magmas into and capping the sedimentary rocks, forming impressive cliffs, especially in the Dry Valleys. The other continents drifted away one by one, leaving Antarctica anchored over the South Pole. Complex rift systems developed in West Antarctica, including that of the Ross Sea.

Sills of black dolerite (a basic igneous rock) intruded into buff-coloured Beacon sandstones, Finger Mountain, Victoria Land. These rocks herald the break-up of Gondwana in the Jurassic Period.

Ferrar dolerite dykes intruded into metamorphic rocks of the Ross Orogeny. They are here well exposed along the flanks of Taylor Glacier, Victoria Land. The irregular black patches represent more recent (late Cenozoic) basaltic volcanism.

Photos Michael Hambrey