The Alps mountains, stretching across south-central Europe and spanning eight countries from Monaco to Slovenia, began forming roughly 65 million years ago. While the initial process started in the late Cretaceous period, the main uplift that created the high peaks occurred over the last 30 million years. The Alps are a classic example of continental collision, a powerful mechanism of plate tectonics that continues to shape the Earth’s surface.
Defining the Alpine Orogeny
The mountain-building process that created the Alps is known as the Alpine Orogeny. This event is part of the larger Alpide belt, a chain of mountains extending to the Himalayas. The orogeny began in the late Cretaceous period, approximately 94 to 70 million years ago, when the first stages of convergence started. The main uplift phase occurred during the Cenozoic Era, peaking between 50 and 40 million years ago in the Paleogene and Neogene periods.
The Tectonic Plates Involved
The Alps formed as a direct consequence of the collision between the African and Eurasian tectonic plates. This convergence began when the African plate, including the microplate known as Adria, moved north toward the European plate. Between these continental blocks lay the ancient Tethys Ocean, which existed during the Mesozoic Era.
Continental Collision
As the plates converged, the oceanic crust of the Tethys began to subduct, or sink, beneath the overriding African plate. This process pulled the denser Tethyan oceanic lithosphere deep into the Earth’s mantle, closing the ocean basin. Once the buoyant continental crusts of Africa and Europe met, they could not easily subduct.
The intense pressure from this continental collision caused the crust to shorten and thicken, much like squeezing a thick rug. Sedimentary rocks from the Tethys Ocean floor were caught, folded, and thrust upward to form the high peaks of the Alps. The Matterhorn’s peak, for example, contains rocks originally part of the African plate, thrust over the European plate’s rocks at its base.
Sculpting the Modern Landscape
Tectonic forces created the initial bulk of the Alps, but the distinctive, rugged appearance was carved by erosion, primarily ice. The most significant shaping occurred during the Pleistocene Epoch, starting about 2.6 million years ago, when the Earth experienced repeated Ice Ages. Glaciers expanded to cover much of the range, scouring away rock and transforming the landscape.
Glacial Action and Isostatic Rebound
As the ice moved, it deepened the valleys, changing their cross-section from a river-carved “V” shape to the characteristic glacial “U” shape. Glacial action also sharpened peaks into distinctive horns and arêtes, the sharp ridges visible today. The Alps are still rising in some areas due to isostatic rebound, where the Earth’s crust springs back after the immense weight of the Ice Age glaciers melted. This ongoing process contributes a few millimeters of rise per year, but it is largely balanced by continuous weathering and erosion from water, wind, and modern glaciers.