Researchers have presented a new theory as to how the Earth’s crust was formed.
A pair of McGill University earth scientists have presented a theory that some of the chemical components of silica-rich minerals that make up the crust settled onto the Earth’s early surface from the steamy atmosphere that was prevalent at the time.
More than 90 percent of the Earth’s continental crust is comprised of silica-rich minerals, including feldspar and quartz and researchers have long believed that it was formed by volcanic activity.
The conventional theory is that a Mars-sized planetoid crashed into the pronto-Earth approximately 4.5 billion years ago, melting the Earth and turning it into an ocean of magma. The impact created enough debris to form the moon and the Earth’s surface gradually cooled until it was basically solid.
Don Baker, an earth scientist at McGill, said his new theory follows that basic principal but takes it a step further by saying after the collision the atmosphere of Earth consisted of a high-temperature stream that dissolved rocks on the Earth’s immediate surface.
“These dissolved minerals rose to the upper atmosphere and cooled off, and then these silicate materials that were dissolved at the surface would start to separate out and fall back to Earth in what we call a silicate rain,” Baker said in a statement.
Baker and co-author Kassandra Sofonio, a McGill undergraduate research assistant, tested this theory with developed a series of experiments aimed at mimicking the steam conditions of early Earth.
They used a combination of bulk silicate earth materials and water and melted the mixture in air at 1,550 degrees Celsius and grounded it into a powder. They then enclosed a small amount of the powder, along with water in gold palladium capsules and placed the capsules in a pressure vessel that was heated to about 727 degrees Celsius and 100 times Earth’s surface pressure.
This simulates the conditions in the Earth’s atmosphere about one million years after the moon-forming impact.
After each experiment, the samples were rapidly quenched and the material that dissolved in the high temperature steam was analyzed.
According to Baker, the researchers were surprised by the similarity of the dissolved silicate material produced by the experiments to what is found in the Earth’s crust.
The study was published in Earth and Planetary Science Letters.
