When too much water is pumped out of an aquifer, you can make a sink hole above it, as there is now air/empty space where water used to be.
4.6 billion years ago
The study pushes back the clock on the origin of Earth's water by hundreds of millions of years, to around 4.6 billion years ago, when all the worlds of the inner solar system were still forming. Scientists had suspected that our planet formed dry, with high-energy impacts creating a molten surface on the infant Earth.
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Lava that hardens on the surface is called an extrusion. The rock layers below an extrusion are always older than the extrusion. ... There, the magma cools and hardens into a mass of igneous rock called an intrusion. An intrusion is always younger than the rock layers around and beneath it.
