Scientists can use a variety of clues to figure out what’s beneath the Earth’s surface without having to dig, including firing ultra-fine lasers thinner than a human hair at minerals found in beach sand.
The technique has been used in a new study that points to a 4 billion-year-old piece of Earth’s crust the size of Ireland, which sat beneath Western Australia and influenced the geological evolution of the region through millions of millennia.
This could perhaps provide clues as to how our planet went from uninhabitable to living.
Researchers believe that the huge expanse of crust would have strongly influenced the formation of rocks as old materials were mixed with new, having first appeared as one of the earliest protocrust formations on the planet and having survived multiple mountain building events.
“Comparing our findings with existing data, it appears that many parts of the world experienced a similar time of early crustal formation and preservation,” says Maximilian Dröellner, PhD student in geology and lead author, from the University Curtin in Australia.
“This suggests a significant change in Earth’s evolution about 4 billion years ago, as meteor bombardment waned, the crust stabilized, and life on Earth began to establish itself.”
The lasers were used to vaporize grains of the mineral zircon, taken from sand taken from rivers and beaches in Western Australia.
Technically known as laser ablation inductively coupled plasma mass spectrometry, the method allows scientists to date grains and compare them with others to see where they might have come from.
This gave the team a glimpse of the crystalline bedrock below the Earth’s surface in this particular region – showing where the grains had originally eroded from, the forces used to create them and how the geology of the region changed. was developed over time.
In addition to the importance of the rest of the protocrust still being there – about 100,000 square kilometers (38,610 square miles) of it – the block boundaries will also help scientists determine what is hidden below the surface of the Earth, and how it might have evolved to be in its current state.
“The edge of the ancient piece of crust appears to define an important crustal boundary controlling where economically important minerals are found,” says lead research geologist Milo Barham, of Curtin University.
“Recognizing these ancient crustal remnants is important for the future of optimized sustainable resource exploration.”
As you might expect after 4 billion years, there isn’t much of the original Earth’s crust left to study, which makes discoveries like this all the more interesting and useful for experts – we giving an important window into the distant past.
The shifting of the Earth’s crust and the swirling of the hot mantle below are difficult to predict and map in retrospect. When evidence of interior movement and geology can be found on the surface, scientists are therefore very keen to make use of it.
Further down the line, the results of the study described here could also help scientists who study other planets – how these planets form, how their oldest crust is shaped, and even how extraterrestrial life might s establish there.
“Studying the early Earth is challenging given the enormity of the time that has passed, but it has profound significance for understanding the meaning of life on Earth and our quest to find it on other planets,” Barham says.
The research was published in the journal Terra Nova.