EARTH may have a heartbeat. Evidence from Hawaii and Iceland hints that the planet鈥檚 core may be dispatching simultaneous plumes of magma towards the surface every 15 million years or so.
If the hypothesis is true, it would revolutionise our ideas of what鈥檚 happening far below our feet. Independent scientists contacted by 快猫短视频 were split, with some scornful and others intrigued.
of the University of Bergen and Jan Inge Faleide of the University of Oslo, both in Norway, used seismological data to measure the thickness of Earth鈥檚 crust between Iceland and Greenland (see map). Iceland is on the Mid-Atlantic Ridge, where magma wells up to form fresh crust.
Advertisement
The measurements allowed Mjelde and Faleide to infer the past flow of magma in the plume generally thought to rise beneath Iceland. When this plume is strong, it thickens the crust that it forms at the surface. They found that the crust has thickened roughly every 15 million years, suggesting the plume pulses at around that frequency.
Regular pulsing of plumes is not a new idea, but when the pair compared their results with similar pulsing in Hawaii, which also sits on a plume, they found a surprising correlation. Data collected by Emily Van Ark and Jian Lin of the Woods Hole Oceanographic Institution, Massachusetts, suggests that Hawaii鈥檚 plume pulses have coincided with Iceland鈥檚 (Marine Geophysical Research, ).
鈥淭hese two are on very different parts of the Earth, so I don鈥檛 think the synchrony could be related to something in the mantle,鈥� says Mjelde. 鈥淚t must relate to the core somehow. I can鈥檛 see any other possibility.鈥� This would mean that the Earth鈥檚 core periodically heats up the overlying mantle, generating synchronised plumes that rise to the surface at widely separated spots.
鈥淭he synchrony must relate to the core somehow. I can鈥檛 see any other possibility鈥�
鈥淚f correct, it would be a significant alteration from our current thoughts,鈥� says of Imperial College London. Most geologists who believe that mantle plumes exist think that pulsing can be explained by processes in the mantle alone, such as magma build-up in regions of different viscosity. 鈥淎 new way of thinking would be needed,鈥� agrees Mjelde. However, several geologists contacted by 快猫短视频 said they could not explain how the enormous pulses of heat required could be generated in the core.
There could be other explanations for the synchronicity. More detailed measurements may reveal the timings of the two plumes鈥� pulses are close but not synchronous. Furthermore, Mike Coffin of the National Oceanography Centre in Southampton, UK, points out that the mantle is not homogeneous, so plumes leaving the core at the same time might not reach the crust at the same time.
鈥淚 am sceptical that they are co-pulsing from the evidence presented,鈥� says Huw Davies of Cardiff University, UK. Still, the idea is 鈥減otentially very exciting鈥�, he adds.
