We’ve known for a long time that Earth’s fiery interior is destined to burn out in the distant future, although new research indicates that this process may be occurring faster on one side of the planet than the other. By analyzing the movement of continents and oceanic plates over the past 400 million years, researchers have determined that parts of the planet have remained more insulated than others, leading to an asymmetrical pattern of heat loss.
Deep within Earth’s interior, heat is continually being generated as radioactive elements degrade. At the same time, however, heat is being lost as it dissipates upwards through the crust. The fact that this surface heat loss outweighs internal heat production means that the planet is cooling overall, and will one day become cold and lifeless.
Interestingly, though, this heat loss does not occur uniformly across the planet, as bulky landmasses provide more insulation than the thinner oceanic crust. In other words, less heat is being lost in areas that are covered by continents, while regions that are covered by oceans cool much faster.
Writing in the journal Geophysical Research Letters, the authors of the new study explain how they used models of tectonic plate cycles in order to demonstrate variations in heat loss across the planet over the past 400 million years. Results indicated that the two sides of the Earth have been cooling at different rates throughout this period, with the dividing line between the two hemispheres located at 60 degrees of longitude.
The reason for this disparity is down to the fact that one hemisphere has been predominantly covered in water over the past 400 million years, while the other has remained insulated by land. The researchers have labeled these the Pacific hemisphere – due to the fact that it consists largely of the Pacific Ocean – and the African hemisphere, which contains the continents of Africa, Europe, and Asia.
By further splitting each hemisphere into grid-like units, each spanning half a degree of latitude and longitude, the researchers were able to calculate the rate of heat loss occurring across each region as tectonic plates have shifted. In doing so, they determined that the Pacific hemisphere has cooled by 50 Kelvin more than the African hemisphere over the past 400 million years.
This is perhaps unsurprising, given that the African hemisphere has always been insulated by the supercontinent Pangea, which later broke up into the African and Eurasian landmasses. In contrast, the Pacific hemisphere has been something of a waterworld for the past billion years or so, and has therefore allowed more heat to dissipate.
Incredibly, though, the study authors found the Pacific hemisphere is in fact hotter than the African hemisphere, despite its faster rate of cooling. By way of explanation, they propose that much of the Pacific mantle was once insulated by a long-lived supercontinent called Rondinia, which trapped a great deal of heat before it broke up around a billion years ago.
It’s therefore possible that the heat trapped by this ancient insulating layer has not yet fully dissipated, and continues to affect the internal temperature of the Pacific hemisphere.