Scientists can use various clues to find out what’s beneath the Earth’s surface without having to do any drilling — including shooting ultra-precision lasers thinner than a human hair at minerals in beach sand.
This technique has been used in a new study that points to a 4-billion-year-old piece of Earth’s crust roughly the size of Ireland, which has been sitting beneath Western Australia and affecting the region’s geological evolution over millions of years.
It may be able to provide clues about how our planet went from being uninhabitable to supporting life.
The researchers believe that the massive extension of the crust would have greatly affected the formation of the rock as the old material was mixed with the new, as it first emerged as one of the planet’s oldest prostatic formations that has survived many mountain-building events.
“When comparing our findings with existing data, it appears that many regions around the world experienced a similar timing of early cortex formation and preservation,” says geology doctoral student and lead author Maximilian Droelnerfrom Curtin University, Australia.
“This indicates a significant change in the evolution of the Earth about 4 billion years ago, as meteorite bombardment waned, the crust settled, and life on Earth began to establish.”
A laser was used to vaporize grains of the mineral zircon taken from sand samples taken from rivers and beaches in Western Australia.
Technically known as laser ablation with laser induction coupled plasma mass spectrometry, this method enables scientists to date the grains and compare them with others to see where they came from.
This team gave insight into the subsurface crystalline vault in this particular region – showing where the grains were originally eroded from, the forces used to create them, and how the region’s geology has shaped over time.
In addition to the importance of the remains of protozoans still extant – about 100,000 square kilometers (38,610 sq mi) of them – the boundaries of the block will also help scientists determine what is hidden far below the Earth’s surface, and how it may have evolved to be in its current state.
“The edge of the ancient crust piece appears to mark an important crustal boundary that controls where to find economically important minerals,” Geological Research Supervisor Milo Parham says:from Curtin University.
“Identification of ancient crustal remnants is important for the future of optimal exploration of sustainable resources.”
As you might expect after 4 billion years, not much of Earth’s original crust is left to study, which makes results like this even more interesting and useful to experts – giving us an important window into the distant past.
It is difficult to predict the shift of the Earth’s crust and the vortices of the hot mantle beneath it and to map it in retrospect. When evidence of internal movement and geology can be found at the surface, scientists are very keen to take advantage of it.
Moreover, the results of the study described here can help scientists looking for other planets – the way these planets are formed, how their first crust is formed, and even how alien life can arise on them.
“Studying the early Earth is challenging because of the amount of time that has passed, but it is of great importance to understanding the importance of life on Earth and our quest to find it on other planets,” Braham says.
The research was published in the journal Terra Nova.
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