The Mont Blanc massif consists predominantly of ancient granite rocks. The Alps have their origins 770million years ago when upheaval of the earth's crust lifted up schist, gneiss and limestone rocks. These were destined to form the base of the Alps range, and this period of upheaval ended 300million years ago. Granite intrusions and associated metamorphic rocks formed the base of the mountains we now call the Mont Blanc massif as well as the nearby Aiguilles Rouges. But these rocks were then heavily eroded away, eventually being ground down and inundated by the sea, so allowing sedimentary rocks to form. Then, once again, this part of the earth's crust was uplifted as a result of the collision of continental plates. The huge mountain ranges of today's Alps began to form. This happened towards the end of the Tertiary period, 15million years ago. Finally, came the Quaternary era, when successive ice ages saw vast glaciers advance, retreat, and then advance again. Their movement across the landscape ground down and shaped the mountains and the valleys we see today.