The oldest rocks found on earth until 2008 are known to be 4.03 billion years old. These rocks were found in Canada’s Northwest Territories called Acasta Gneiss. Originally, this rock was found as a part of an old mountain chain. Its core was exposed due to glacial activities over billions of years. This oldest rock found till date was formed during the Hadean period (the oldest geological time division of the Earth’s formation). This period was formed 4.57 billion years ago and stretched till the dawn of the Archean period, which is about 3.8 billion years ago. Many oldest rocks found on earth were formed during this time phase.
Other old rocks on Earth have been found in Western parts of Greenland and Australia. The age of these rocks is about 3.8 billion years and used for identifying a demarcation between the Hadean and Archean eras. The crust of Earth found in the continental regions is very old, about billion of years. On the other hand, oceanic crusts are continuously replaced and have an average age of about 100 million years, much less than the continental crust.
Rocks older than Acasta Gneiss are from Jack Hills, Australia. They date back to about 4.4 billion years. These are the oldest rocks on Earth that formed after 130 million years, when after the earth’s formation, its crust started cooling down from a previous molten state.
It is also believed that only 7 per cent or lesser Continental rocks on Earth are older than 2.5 billion years. Earlier, the Earth’s crust was more heated (almost three times than what it is at present); this led to rapid recycling of the crust and new rock formation due to mass erosions and volcanic activities.
Scientists and researchers are constantly trying to study further about ancient Earth’s conditions and more rocks that can aid in this study.
