In the conventional view of the water cycle (also known as the hydrologic cycle), water moves between reservoirs in the atmosphere and Earth's surface or near-surface (including the ocean, rivers and lakes, glaciers and polar ice caps, the biosphere and groundwater). However, in addition to the surface cycle, water also plays an important role in geological processes reaching down into the crust and mantle. Water content in magma determines how explosive a volcanic eruption is; hot water is the main conduit for economically important minerals to concentrate in hydrothermal mineral deposits; and water plays an important role in the formation and migration of petroleum.[1]