The evidence is seen in tiny iron minerals that are aligned inside ancient dacite rocks from the Barberton mountains in South Africa.
Analysis of minerals, however, indicates that the strength of the field was much weaker than today.
Earth”s magnetic forms a shield that deflects harmful particles from the Sun around our world, and limits the ability of this ‘solar wind’ to erode our atmosphere.
The new work by Professor John Tarduno, from the University of Rochester, US, and colleagues has been discussed at a major Earth sciences meeting in Vienna, Austria.
“Earth”s magnetic field is important to us,” the BBC quoted Professor John Tarduno, from the University of Rochester, US, as saying at a major Earth sciences meeting in Vienna, Austria.
“[3.45 billion years ago] is a really critical time because it”s when we start seeing the first tentative signs of life, so perhaps these two things are linked together,” he added.
Tarduno and colleagues developed techniques for studying tiny magnetite minerals trapped inside the crystals of volcanic rock.