Reversals of Earth's Magnetic Field Explained by Small Core Fluctuations

(PhysOrg.com) -- Based on studies of old volcanic basalt, scientists know that the Earth’s magnetic field reverses at irregular intervals, ranging from tens of thousands to millions of years. Volcanic basalt rock contains magnetite, and when the rock cools, its magnetic properties are frozen, recording the Earth's magnetic field of the time. With this data, scientists estimate that the last magnetic field reversal occurred about 780,000 years ago.

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<p><a href="http://www.physorg.com/news159704651.html">Reversals of Earth's Magnetic Field Explained by Small Core Fluctuations</a></p> <p>(PhysOrg.com) -- Based on studies of old volcanic basalt, scientists know that the Earth’s magnetic field reverses at irregular intervals, ranging from tens of thousands to millions of years. Volcanic basalt rock contains magnetite, and when the rock cools, its magnetic properties are frozen, recording the Earth's magnetic field of the time. With this data, scientists estimate that the last magnetic field reversal occurred about 780,000 years ago.</p>