There were various explanations for volcano behavior before the structure of the earth mantle as a semisolid material was developed. For decades, awareness that compression and radioactive materials may be heat sources was discounted and volcanic action was often attributed to chemical reactions and a thin layer of molten rock near the surface.
PTELook at the text below. In 35 seconds, you must read this text aloud as naturally and clearly as possible. You have 35 seconds to read aloud.
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Beginning in 35 seconds.