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Earth's Poles Shifted Dramatically Four Times!
1 Oct
Summary
- Geographic poles can move via true polar wander.
- Sea-level changes act as clues to polar shifts.
- Poles moved dramatically four times in Earth's past.
The Earth's geographic poles, the points defining its rotational axis, are not as fixed as once believed. A new study suggests that ancient sea-level changes provide crucial evidence for past movements, a phenomenon known as true polar wander. This process occurs as mass redistribution within Earth's mantle influences the planet's spin.
Scientists analyzed geological records of sea-level fluctuations, identifying a distinctive pattern expected during true polar wander. This pattern involves reversals of sea-level rise and fall across hemispheres, creating a global beach ball-like effect. This unique signal differs from other Earth processes.
The research found evidence of dramatic polar movements occurring approximately 20, 90, 140, and 190 million years ago. These shifts happened over periods of around 10 million years, with rates potentially exceeding 0.6 degrees per million years.
While these past movements were significant, true polar wandering continues today, measurable by satellites at about 10 cm per year. This ongoing, albeit slower, movement indicates that deep Earth processes continue to influence long-term climate and sea levels.
