Boriana Kalderon-Asael conducts field work at a Middle-Upper Ordovician outcrop near Reedsville, Penn. (Photo by Ashleigh Hood)
One of Earth’s greatest mysteries is how it transformed itself, ever so gradually, from a barren ball of rock into a launching pad for life.
Earth scientists have spent decades piecing together the relevant clues — identifying and studying the planet’s complex interplay of geological processes, atmospheric dynamics, and chemical cycles. In particular, scientists have studied the roles played by carbon and silicon in stabilizing Earth’s climate over a vast stretch of time.
Now a Yale-led study in the journal Nature provides an unprecedented look at this 3-billion-year-old story, told in ancient sediments from around the world.
“We wanted to advance our understanding of what processes have regulated Earth’s climate over geologic time scales,” said Noah Planavsky, an associate professor of Earth and planetary sciences in Yale’s Faculty of Arts and Sciences and co-corresponding author of the new study with Yale graduate student Boriana Kalderon-Asael and University College London researcher Philip Pogge von Strandmann.
“How the Earth’s climate has remained stable for the majority of the last 3 billion years is one of the most fundamental questions one can ask about how the Earth works,” Planavsky said.
At the root of Earth’s climate life story is its ability to remove carbon dioxide from the atmosphere and store it in rocks and sediments. We have plants to thank for that, the researchers said.
The emergence of plants on land and in the ocean led to gradual — but major — changes in how rocks and sediments weathered. These changes in weathering opened the door for sequestering carbon into the Earth itself.
“The result was a substantial decrease in carbon dioxide levels, which kept pace with the increasing luminosity of the sun as it aged, helping to ensure that the Earth remained persistently habitable to both simple and complex life forms,” Planavsky said.
Kalderon-Asael and Planavsky led an international team of researchers that gathered more than 600 sediment samples at roughly 100 sites worldwide. The researchers studied geochemical data found in lithium isotopes in the samples — a methodology used in other studies over the past decade to look at specific points in Earth’s recent and distant past.