Earth’s first continents arose much earlier than we thought
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Earth’s first continents
Before Earth had continents, it only had the ocean. Then, the first continents emerged from the ocean. These continents were known as the cratons.
A new study says that they emerged from the ocean between 3.3 billion and 3.2 billion years ago. This means cratons emerged hundreds of millions of years earlier than we had thought before.
Earlier, scientists had found sedimentary rocks from that time. These could have formed only after the continents emerged. Sedimentary rocks are those that form from the broken-up bits of other rocks affected by the climate and environment. However, despite this, scientists had believed that only parts of the cratons, must have emerged that early.
But now, the study says that entire cratons, not just small patches of land, emerged from the oceans 3.3 billion years ago. For this study, scientists studied rocks from the Singhbhum Craton, located in eastern India. To find out the age of the rocks, they tried to find tiny crystals called zircons in them. These zircons contain uranium, which decays (age) at a fixed rate. This rate helped them find the age of the uranium, and hence, the rocks.
How did they emerge?
Moreover, they also conducted computer modelling to find out how Earth’s first continents emerged. They found that about 3.5 billion to 3.2 billion years ago, hot magma beneath the crust caused portions of the craton to thicken and get lighter minerals. This made it possible for them to float up to the surface.
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