The Equator is Growing!
News story originally written on August 7, 2002
Earth may look perfectly spherical from space, like a giant marble, but it actually isn't! Instead, our planet is wider around the equator because matter is forced out as Earth spins (just as you feel you are pushed right when your car turns fast to the left). The Earth does not stay the same shape however, and scientists have been watching Earth's equator as it shrinks and grows!
Standing on Earth's surface, we cannot see the small changes in Earth's shape but researchers have been watching the equator grow smaller with satellites over the past 20 years or so, and they believe this has been happening since the last ice age 18,000 years ago. Since the ice age, temperatures warmed and glaciers at the poles melted slowly. Little by little the poles became less squashed under heavy ice. Molten rock moved under the Earth's crust from the equator to the poles to fill in the new space and the equator grew smaller.
For the past four years, however, Earth has been doing something quite different. Researchers have found that the equator is now growing larger! Since we know that glaciers are still melting at the poles, scientists are puzzled why the process would change.
For Earth's equator to increase in size, material must have been moved there from somewhere else on the planet. One hypothesis is that molten rock has been moving deep within the Earth from below the poles to below the equator because of small changes in Earth's magnetic field. Another hypothesis is that there is more water at the equator as melting glaciers add more water into the oceans, which moves towards the equator with currents.
Whatever the reason, the researchers believe that this change in the shape of Earth is natural variation, not anything that humans have done to the planet.