1.7 So, how old is the Earth?
The rock cycle is a fairly simple scheme, but it may seem rather complicated because of the variety of routes rock materials can take to be transformed. Many of these stages, such as the formation of a metamorphic rock, can take vast amounts of time. Other rock-forming processes, like the eruption of a volcano, can form new rock almost instantaneously.
This brings us to an important point – the vast amount of time that some geological processes can take. The amount of time taken for a whole mountain range to be eroded flat is almost unimaginable, but the evidence from the rock record of sedimentary rocks that made up bits of that mountain range, and of the metamorphic roots of those mountains found at the surface, show that it must have happened. And more than that, the evidence suggests it’s happened time and time again – with material repeatedly moving around the rock cycle.
That’s because although some of these processes take a really long time, the Earth is so old that it’s possible for it to have happened over and over again.
In this video, Marcus discusses the essential events in earth history as if they took place over the course of a single day.