Geologists continue to study the formation of Earth's continents, which are unique due to their buoyant, silica-rich composition. Tim Johnson, a geologist at Curtin University in Perth, Australia, noted that the oldest known continental rock dates back approximately 4 billion years. The reason for the emergence of continents at that time remains unclear, as does the mechanism behind the creation of continental crust.
Johnson and his colleagues propose that the formation of continents was significantly influenced by a series of asteroid impacts that kept the early crust sufficiently hot and thin, enabling the development of buoyant landmasses. This theory suggests that the continents we inhabit today were formed as a result of ancient cosmic bombardment.
The challenge in studying continental formation lies in the scarcity of geological evidence. The oldest continental-type rocks crystallized around 4.03 billion years ago, marking the end of the Hadean eon, which encompasses the first 500 million years of Earth's history. While some basaltic rocks date back to about 4.2 billion years, and a few zircon crystals extend the record to 4.4 billion years, little else remains. Consequently, scientists must rely on educated hypotheses to understand the early Earth. Johnson remarked on the significant debates surrounding this topic due to the limited data available.