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A cloud is a visible mass of water droplets or frozen ice crystals suspended in the atmosphere above the surface of the Earth or another planetary body. Clouds in the Earth's atmosphere are studied in the nephology or cloud physics branch of meteorology. Two processes, possibly acting together, can lead to air becoming saturated: cooling the air or adding water vapor to the air. Generally, precipitation will fall to the surface; an exception is virga which evaporates before reaching the surface...

A volcano is an opening, or rupture, in a planet's surface or crust, which allows hot magma, volcanic ash and gases to escape from below the surface. Volcanoes are generally found where tectonic plates are diverging or converging. A mid-oceanic ridge, for example the Mid-Atlantic Ridge, has examples of volcanoes caused by divergent tectonic plates pulling apart; the Pacific Ring of Fire has examples of volcanoes caused by convergent tectonic plates coming together...