At top: Changes over time in the average silica (SiO2) content of the continents. The orange star represents the current value for continental crust, namely 67% of its mass, while the green star indicates the current value for oceanic crust, 50% of its mass. Continental crust has always been rich in silica compared to the more silica-poor oceanic crust. At bottom: Periods of major crustal growth (grey vertical bars) as recorded in sedimentary rocks over the past 3.7 billion years. (IMAGE)

CNRS

At top: Changes over time in the average silica (SiO2) content of the continents. The orange star represents the current value for continental crust, namely 67% of its mass, while the green star indicates the current value for oceanic crust, 50% of its mass. Continental crust has always been rich in silica compared to the more silica-poor oceanic crust. At bottom: Periods of major crustal growth (grey vertical bars) as recorded in sedimentary rocks over the past 3.7 billion years.

Caption

At top: Changes over time in the average silica (SiO2) content of the continents. The orange star represents the current value for continental crust, namely 67% of its mass, while the green star indicates the current value for oceanic crust, 50% of its mass. Continental crust has always been rich in silica compared to the more silica-poor oceanic crust. At bottom: Periods of major crustal growth (grey vertical bars) as recorded in sedimentary rocks over the past 3.7 billion years. © Marion Garçon

Credit

© Marion Garçon

Usage Restrictions

only be used with credit and caption appropriate

License

Original content

Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.