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HOW THE ALPS WERE FORMED
Summary

Geology might not be everyone’s favourite topic — but when you’re out in the Alps, surrounded by colossal peaks, it takes on a new life. Knowing even the basics of how these landscapes came to be can make the experience richer, and even give you a mental boost on the trail. Here's the quick summary - if you read nothing else, just read the this next paragraph :-)

Mountain building began about 65 million years ago and intensified around 50 million years ago. Glaciers and rivers later carved these uplifted rocks into the mountains we see today — and you can see this history written in the landscape all around you, from U-shaped valleys and jagged ridges to deep lake basins and towering cliff faces. The main building phase ended 5–9 million years ago, but the Alps are still rising slightly even as erosion wears them down.

From Sea to Mountains

Around 250 million years ago, much of Europe lay under the Tethys Sea. Sediment from rivers built thick layers of sedimentary rock such as limestone, sandstone, and shale.

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By 180 million years ago, tectonic forces began to pull the plates apart. Small ocean basins formed between the African and European plates, with the Adriatic plate sitting between them.

Continents on the Move
The Collision Begins

About 65 million years ago, the African plate started moving north towards Europe, closing the ocean in between. The seabed was squeezed, folded, and lifted — the start of the Alpine orogeny, or mountain-building phase.

Around 50 million years ago, the collision intensified as the continental crusts met directly. Huge slabs of sedimentary, igneous, and metamorphic rock were stacked like carpets being pushed together. As the crust thickened, peaks rose rapidly. The main uplift phase lasted until around 5–9 million years ago, after which it slowed to the minor rises still seen today.

Uplift of the Peaks
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Ice and Water Shape the Alps

Over the last 2 million years, ice ages sent massive glaciers down the valleys. They carved U-shaped valleys, gouged deep lake basins, and left behind sharp ridges. Meltwater rivers carried rock and sediment away, creating the dramatic landscapes we see today.

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The Alps are still rising at about 1–2 mm per year, especially in the west. Erosion and meltwater slowly lower some areas. Mont Blanc’s bedrock is rising, but its measured height changes from year to year because of its snow and ice dome, which can gain or lose several metres depending on the season.

The Alps Today
Rocks and Plant Life in Switzerland

On our Swiss adventures, we move through areas shaped by different rock types — and these can affect both the landscape and your experience on the trail.​​​

  • Limestone (sedimentary) – Alkaline soils support gentians, edelweiss, and alpine asters. Terrain is often sharp and uneven, with scarce surface water as streams sink underground.

  • Granite and gneiss (igneous & metamorphic) – Acidic soils favour alpine azalea, bilberry, and saxifrages. Stable underfoot but can form slippery slabs; streams are more common than in limestone areas.

  • Schist (metamorphic) – Thin, nutrient-poor soils host hardy cushion plants. Often loose and unstable, with scree-covered trails requiring careful footing.

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Take Away Points

  • Geology may seem boring, but in the Alps it helps bring the scenery to life

  • African and European plates collided to form the Alps

  • Mountain building began ~65 million years ago, intensified ~50 million years ago

  • Major uplift ended 5–9 million years ago

  • Composed of sedimentary, igneous, and metamorphic rocks

  • Ice ages shaped modern valleys and peaks

  • Still rising overall, though erosion lowers some peaks

  • Mont Blanc’s measured height varies due to its snow dome

  • Rock type influences soil, footing, water availability, and plant diversity

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