Scientists have unveiled how continents were formed on Earth over 2.5 billion years ago – and how those processes have continued for the last 70 million years to profoundly affect the planet’s life and climate.
A new study details how relatively recent geologic events – volcanic activity 10 million years ago in what is now Panama and Costa Rica – hold the secrets of the extreme continent-building that took place billions of years earlier.
The discovery provides new understanding about formation of the Earth’s continental crust – masses of buoyant rock rich with silica, a compound that combines silicon and oxygen.
The continental mass of the planet formed in the Archaean Eon, about 2.5 billion years ago. The Earth was three times hotter, volcanic activity was considerably higher, and life was probably very limited.
Many scientists think that all of the planet’s continental crust was generated during this time in Earth’s history, and the material continually recycles through collisions of tectonic plates on the outer-most shell of the planet.
But the new research shows “juvenile” continental crust has been produced throughout Earth’s history.
The researchers used geochemical and geophysical data to reconstruct the evolution what is now Costa Rica and Panama, which was generated when two oceanic plates collided and melted iron- and magnesium-rich oceanic crust over the past 70 million years, Gazel said.
Melting of the oceanic crust originally produced what today are the Galapagos islands, reproducing Achaean-like conditions to provide the “missing ingredient” in the generation of continental crust.
The researchers discovered the geochemical signature of erupted lavas reached continental crust-like composition about 10 million years ago.They tested the material and observed seismic waves travelling through the crust at velocities closer to the ones observed in continental crust worldwide.