Scientists have used ultra-thin lasers to reveal an Ireland-sized piece of Earth’s crust deep within Australia that could be up to 4 billion years old. Considering our planet is estimated to be 4.5 billion years old, this discovery may provide some important information about the tectonic forces that bent the Earth very early on, which helped shape its surface’s rocky outer crust.
As reported in the journal Terra Nova, researchers at Curtin University in Perth collected tiny grains of zircon extracted from beach sand in Western Australia (WA) and examined them with lasers “thinner than a human hair.”
Combined with isotopic analysis, this process revealed where the minerals were eroded and showed their origins in a 100,000-square-kilometer fragment of protocrucian Earth between 4 billion and 3.8 billion years old.
Lead author Maximilian Droellner, of the Timescales of Mineral Systems Group at Curtin’s School of Earth and Planetary Sciences, said in a statement that “a piece of crust the size of Ireland, approximately four billion years old, has influenced the geological evolution of WA over the past few billion years, and the rocks formed in WA over this time period have been significant. “This piece of crust has survived many mountain building events between Australia, India and Antarctica and appears to still exist at a depth of tens of kilometers below the South-West corner of BA.”
The age of this piece of the Earth’s crust can be quite significant. This epoch coincides with a time when the planet transitioned from the Hadean Age – the “hell” state where Earth was little more than a fiery ball of molten rock – to the first period of the Archean Age, when a solid crust emerged.
Estimates vary, but life on Earth is thought to have emerged about 3.75 billion years ago. Given these dates, it’s possible that the pre-crust beneath BA may reveal some information about how our planet went from uninhabitable to life-supporting.
“This example shows a significant change in Earth’s evolution about four billion years ago as meteorite bombardment waned, the crust stabilized, and life began to form on Earth,” says Droellner.
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