Bedrock recently studied in a portion of northern Quebec has been dated at 4,280 million years, making it the oldest known rock on Earth's crust, formed when the Earth was less than 300 million years old.
Scientists are intrigued, but some are not yet entirely convinced that the rocks are quite that old. The bedrock may be younger sedimentary rocks, formed from remnants of older rock that is indeed 4,28o billion years old.
Geologists avoid using the term "billion" because in one part or another of the English-speaking world, it refers to quantities that differ by three orders of magnitude - a billion in Great Britain is a 1,000,000 million.
Currently, the oldest known rock on Earth has been found in the Canadian Northwest, dated at 4,030 million years old. Geologists have also found crystals of zircon as old as 4,360 million years old embedded within younger rocks in Western Australia. The age of the Earth is more than 4,500 million years.
Radioactive elements trapped within zircons provide precise ages, but zircons have not yet been found in the Quebec rock. Instead, the age of the rock was determined from the amounts of neodymium and samarium, two rare earth elements.
If the rocks are as old as claimed, what is significant is that they’re not dramatically different from rocks you would find today in Japan or places like that. In fact, their chemical signature looks most similar to ocean floor that has been pulled under continents. That suggests that the process of plate tectonics, reshaping and moving continents, could have already started on the very early Earth. At the very least, the existence of rock 4,280 million yeas ago would run counter to the traditional image of the young Earth as a roiling cauldron of magma, a view that is falling by the wayside among researchers as more geological data is unearthed.
Maybe the young Earth wasn't so hot after all.
Scientists are intrigued, but some are not yet entirely convinced that the rocks are quite that old. The bedrock may be younger sedimentary rocks, formed from remnants of older rock that is indeed 4,28o billion years old.
Geologists avoid using the term "billion" because in one part or another of the English-speaking world, it refers to quantities that differ by three orders of magnitude - a billion in Great Britain is a 1,000,000 million.
Currently, the oldest known rock on Earth has been found in the Canadian Northwest, dated at 4,030 million years old. Geologists have also found crystals of zircon as old as 4,360 million years old embedded within younger rocks in Western Australia. The age of the Earth is more than 4,500 million years.
Radioactive elements trapped within zircons provide precise ages, but zircons have not yet been found in the Quebec rock. Instead, the age of the rock was determined from the amounts of neodymium and samarium, two rare earth elements.
If the rocks are as old as claimed, what is significant is that they’re not dramatically different from rocks you would find today in Japan or places like that. In fact, their chemical signature looks most similar to ocean floor that has been pulled under continents. That suggests that the process of plate tectonics, reshaping and moving continents, could have already started on the very early Earth. At the very least, the existence of rock 4,280 million yeas ago would run counter to the traditional image of the young Earth as a roiling cauldron of magma, a view that is falling by the wayside among researchers as more geological data is unearthed.
Maybe the young Earth wasn't so hot after all.
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