This disruption could have promoted the convection that still drives Earth's dynamo today.Įventually, the inner core will probably grow large enough that convection in the outer core is no longer efficient, and the magnetic field will fail. This impact, which occurred perhaps 100 million years after Earth came together, could have shaken up any stratification, or layering, of materials in Earth's core: Imagine shaking up a bottle of oil and water on a planetary scale. It isn't clear why the dynamo got started, Tarduno told Live Science, though it's possible that the enormous planetary impact that created the moon might have been the key driver. But Tarduno and his team have found evidence for a magnetic field on Earth in the planet's oldest minerals, zircons, dating back 4.2 billion years, suggesting that activity in the core has been creating magnetism for a very long time. Scientists think that the current core arrangement may have settled into place about 1.5 billion years ago, according to 2015 research that found a leap in the magnetic field's strength around then. This magnetic-field engine, known as a dynamo, has been chugging along for billions of years.
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