If the Earth's core were to cool down and the magma inside the Earth were to cool and harden, it would have serious consequences.
- The Earth's magnetic field, generated by the molten iron in the outer core, would weaken or disappear, leaving the surface exposed to harmful cosmic radiation.
- Tectonic activity would halt, which could cause earthquakes and volcanic eruptions to cease. This will impact nutrient recycling. Over time, this could also lead to the formation of a supercontinent, as there would be no mechanism to break apart the continents.
- Geothermal energy availability would be affected.
- The Earth's rotation would slow down, leading to longer days and shorter nights. This would have significant effects on the climate and the seasons.