巨大热岩块可能曾使地球磁场变得不规则

Earth’s magnetic field wonky Alex Wilkins TWO vast, mysterious masses of hot rock around Earth’s core may have been instrumental in producing Earth’s magnetic field and giving it an irregular shape for millions of years. Scientists have known for decades about the two continent- sized chunks of rock, one beneath Africa and the other under the Pacific Ocean. These blobs, which extend nearly 1000 kilometres from the outer core to the rocky mantle above, must be different from their surroundings because seismic waves travel through them more slowly. But as it is difficult to measure them due to their depth, scientists can’t identify exactly how they differ. …