Zircons, plate tectonics and the mystery of life – Physics World
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Identifying the oldest evidence for the recycling of hydrated crust into magma on Earth is important because it is most effectively achieved by subduction. However, given the sparse geological record of early Earth, the timing of first supracrustal recycling is controversial. Silicon and oxygen isotopes have been used as indicators of crustal evolution on Archean igneous rocks and minerals to trace supracrustal recycling but with variable results. We present Si-O isotopes of Earth's oldest rocks [4.0 billion years ago (Ga)] from the Acasta Gneiss Complex, northwest Canada, obtained using multiple techniques applied to zircon, quartz, and whole rock samples. Undisturbed zircon is considered the most reliable recorder of primary Si signatures. By combining reliable Si isotope data from the Acasta samples with filtered data from Archean rocks globally, we observe that widespread evidence for a heavy Si signature is recorded since 3.8 Ga, marking the earliest record of surface silicon
Plate tectonics refers to how humongous slabs of solid rock glide over Earth s mantle, the layer just below the crust. These continental slabs shift, fracture and collide, causing
earthquakes to occur, mountains to grow and oceans to form. Besides Earth, no other known planetary bodies have plate tectonics, the researchers said. It s likely that Earth has life because of plate tectonics,
For instance, over time, rocks capture carbon dioxide, a greenhouse gas that helps to warm Earth (although too much CO2 can lead to
global warming), and plate tectonics ensures that these rocks eventually get dragged down and melted, and their CO2 is spewed out as gas through volcanoes,
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