What is the History of the Earths Crust?
The Earth’s crust, its outermost layer, formed about 4.44 billion years ago, roughly 100 million years after the formation of the Earth itself. Prior to 4.44 billion years ago, the Earth’s crust was entirely molten, due to residual heat from the planet’s initial collapse. Evidence that the Earth’s crust cooled within 100 million years comes from measurements of hafnium levels in the Jack hills in Western Australia, one of the oldest areas of exposed crust today. During the initial formation of the Earth’s crust, an event known as the Iron Catastrophe occurred, where the denser elements of the Earth’s composition, such as iron and nickel, sank to its core, while the lighter elements, like silicon, formed a crust at the top. The crust began to cool when the Earth was at least 40% of its current size, possessing enough gravity to hold down an atmosphere containing water vapor. Much of this early water vapor would have come from comets. This era in the Earth’s history, extending from the E
