Volcano were proposed for volcano behavior before the modern understanding of the Earth's mantle structure as a semisolid material was developed. For decades after awareness that compression and radioactive materials may be heat sources, their contributions were specifically discounted. Volcanic action was often attributed to chemical reactions and a thin layer of molten rock near the surface. Volcano A volcano is a rupture in the crust of a planetary-mass object, such as Earth, that allows hot lava, volcanic ash, and gases to escape from a magma chamber below the surface. Earth's volcanoes occur because its crust is broken into 17 major,
Liquid chalk from magnesium carbonate, as compared to the more common powder chalk, which is calcium carbonate. Since liquid chalk does not leave a white residue, it is an environmentally friendly alternative. In four forms of climbing, liquid chalk may prove more useful than powdered chalk. "Many rock climbers prefer to use liquid over dry because of volume and weight. In the past, huge heavy chalk blocks had to be taken on climbs because so much was required to climb" In other sports, liquid chalk is less beneficial to the athlete, because re-chalking can be done more easily between sets or rounds.