This escaping heat powers the geodynamo and coupled with the spinning of Earth generates the magnetic field. Scientists have recently begun to realise that the inner core may be melting as well as freezing, but there has been much debate about how this is possible when overall the deep Earth is cooling.
Now the research team believes they have solved the mystery. Using a computer model of convection in the outer core, together with seismology data, they show that heat flow at the core-mantle boundary varies depending on the structure of the overlying mantle. In some regions, this variation is large enough to force heat from the mantle back into the core, causing localised melting. The model shows that beneath the seismically active regions around the Pacific 'Ring of Fire', where tectonic plates are undergoing subduction, the cold remnants of oceanic plates at the bottom of the mantle draw a lot of heat from the core.
This extra mantle cooling generates down-streams of cold material that cross the outer core and freeze onto the inner core.
Conversely, in two large regions under Africa and the Pacific where the lowermost mantle is hotter than average, less heat flows out from the core.
The outer core below these regions can become warm enough that it will start melting back the solid inner core. Co-author Dr Binod Sreenivasan from the Indian Institute of Technology said: "If Earth's inner core is melting in places, it can make the dynamics near the inner core-outer core boundary more complex than previously thought. On the other hand, melting would produce a layer of dense liquid above the boundary. Therefore, the blobs of light elements will rise through this layer before they stir the overlying outer core.
So the possibility of inner core melting can also place a powerful constraint on the regime in which the Earth's dynamo operates. Co-author Dr Sebastian Rost from the University of Leeds added: "The standard view has been that the inner core is freezing all over and growing out progressively, but it appears that there are regions where the core is actually melting. But they are not moving any more, and there is no magnetic field and only a thin atmosphere left.
We do not know whether the core of Mars is still molten or not, but a robot called InSight recently landed on Mars that will help us to find out! Hello, curious kids! Ask an adult to send your question to us. You can:. Please tell us your name, age and which town or city you live in. You can send an audio recording of your question too, if you want. Send as many questions as you like! More Curious Kids articles, written by academic experts:. What existed before the Big Bang?
What is a species? The Chernobyl accident was far more devastating; it rates as a 7, or a "major accident," on the INES scale. In Ukraine, then part of the Soviet Union, a power surge caused an explosion in one of the plant's reactors, releasing huge doses of radioactive fallout into the air.
Two plant workers died within hours, according to the U. Nuclear Regulatory Commission; 28 more died in the following months from radiation poisoning.
The fallout from Chernobyl was widespread, and the health effects of the disaster are difficult to quantify. A report from the United Nations Scientific Committee on the Effects of Atomic Radiation found that 6, individuals who were under the age of 18 in Ukraine, Belarus or Russia at the time of the disaster had by contracted thyroid cancer, "a substantial fraction" of whom likely contracted the disease due to radiation exposure.
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