The signatures found in Arctic lavas are more than 4.45 billion years old. By comparison, the Earth is 4.54 billion years old, only slightly older.
The oldest surviving remnants of our planet’s turbulent beginnings were unearthed by Dr Matthew Jackson of Boston University, US, and his international team.
They collected the lava samples from Greenland and Baffin Island in the Canadian Arctic. Although they erupted only 60 million years ago, the lavas contain a chemical signature of a far more ancient source.
They show that beneath the Arctic today are small pieces of mantle – the toffee-like layer below the crust – that have survived unchanged since shortly after the formation of the Earth.
The age of this ancient mantle was determined by studying helium gas locked in the lavas. The 4.45 billion-year age means that the samples date from before the Earth’s crust developed, but after the core formed.
The search for the oldest remnants of the Earth’s mantle has become something of a Holy Grail for planetary scientists in recent times.