By this time, Earth’s solid inner core had likely begun to form — a turning point in the planet's internal evolution that also strengthened the magnetic field.
# Metadata
Title: Formation of the Inner Core Movietime: 7:51 Geographical Time: 1250 Ma
While estimates vary, many geophysical models suggest that Earth’s solid inner core crystallized around 1.25 billion years ago. Prior to this, Earth had a fully liquid iron outer core. As the planet cooled, solid iron began to precipitate and grow inward from the center.
This solidification released latent heat and lighter elements into the outer core, intensifying convection. As a result, the geodynamo — the engine driving Earth’s magnetic field — became more vigorous, leading to a noticeable increase in magnetic field strength.
The formation of the inner core also marked a long-term shift toward the more stable and protective magnetic shield we experience today.
# See - Earth History Metadata - Geodynamo - Earth's Core Evolution - Magnetic Field