The continents which number five, six ,seven, or even more depending on the model used are still very poorly understood. They form the emerged part of the Earth’s continental crust. The continents have varied structures as well as rocks of different compositions and ages, and this diversity makes them difficult to study.
Researcher Marion Garcon from the Laboratoire magmas et volcans studied a compilation of data bringing together information on sedimentary rocks with ages ranging from 3.7 billions years ago to the present day.
Her first conclusion is that the continents have always been rich in silica. On average, silica makes up 67% of continental land mass, and its content has never gone below 60% throughout Earth’s history. This discovery contradicts models that suggest that the continents were relatively depleted in silica but rich in iron and magnesium at the beginning of Earth’s history.
Marions second conclusion is that continental growth is not a continuous process. There have been six major periods of continental growth, occurring roughly every 500 – 700 million years over the past 3.7 billion years. These events allowed the continents to grow to the size they are today. They may also be connected to cycles of assembly and breakup of supercontinents such as the most well known of them, Pangea.
https://scitechdaily.com/unraveling-earths-mysteries-continental-growth-is-not-a-continuous-process/