The oldest sedimentary rocks
Mud and sand laid down under water 3.8 billion years ago — proof of oceans, weather and erosion.
- When
- Known to
- ± 50 million years
- Era
- Eoarchean, Archean
Isua preserves rocks made from grains eroded off older land and settled through water. Their existence requires a hydrological cycle: rain, running water, standing oceans and exposed rock being worn down. Combined with pillow lavas in the same sequence, they establish that Earth had a recognisable water-driven surface environment by this point.