Take a wander through the outskirts of south London and you might stumble across a fragment of Earth’s deep past: a collection of rocks forged more than 2 billion years ago. Older than the first stirrings of complex life , they are among the most ancient rocks in Western Europe. But what are they doing in a leafy suburb? The rest of this article is behind a paywall. Please sign in or subscribe to access the full content.

The rocks originated far away on the Hebrides, the rugged archipelago that sits on the northwestern tip of Scotland like a mohawk. Most of the Hebrides is comprised of this primeval geology, including the islands of Raasay, Skye, Rùm, Coll, Tiree, and Iona.

Known as the Lewisian gneisses, or Lewisian gneiss , the rocks are the oldest rocks in Western Europe, some of

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