Earth’s Molten Core Has Peaks and Valleys

Towering underground mountains and valleys six times deeper than the Grand Canyon have been found on Earth’s molten metal core by scientists who devised crude maps of the planet’s interior.

“There has been no previous evidence for bumps on the core,” said Caltech geophysicist Robert Clayton. “They were only speculated. This is direct evidence that they exist.”

The boundary between Earth’s molten nickel-iron core and the surrounding rock mantle is located more than 2,000 miles below the planet’s surface.

Maps of the topography of that boundary were made using a 5-year-old technique called seismic tomography, in which varying speeds of earthquake waves through molten and solid rock were measured. Caltech researchers used worldwide records of thousands of earthquakes occurring between 1971 and 1980 and measuring more than 4.5 on the Richter scale.

The crude maps of Earth’s core provide poor detail and fail to map the core-mantle boundary in some places, especially the Southern Hemisphere.

But far beneath the Philippine Sea, the core shows a “low” or valley at least six miles deep, more than six times the depth of the Grand Canyon. Beneath the Gulf of Alaska, there is a six-mile-high mountain on the core--taller than Mt. Everest.

Other underground mountains were found under eastern Australia, the central North Atlantic, the northeastern Pacific, Central America and south-central Asia. Valleys exist in the core beneath the southwestern Pacific, the East Indies, Europe and Mexico.

According to Clayton and Caltech geophysicists Don L. Anderson and Olafur Gudmundsson, who presented their findings last week in San Francisco at the American Geophysical Union meeting, friction from the sloshing of the liquid across the core’s mountains and valleys also may explain why the Earth rotates with a slight jerkiness that causes a day to vary by one five-thousandth of a second every decade.