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pyrosphere

noun
py·​ro·​sphere | \-ˌsfi(ə)r\

Definition of pyrosphere 

1 : the hot central portion of the earth

2 : a hypothetical spherical zone of molten magma that is held to intervene between the crust of the earth and a solid nucleus and to supply lava to volcanoes

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History and Etymology for pyrosphere

International Scientific Vocabulary pyr- + sphere

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