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How is it possible for there to be a glacier floating on water but under clouds? Depending on the temperature, shouldn't there only be one state of water?

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    $\begingroup$ just to clarify. clouds are liquid water in very small droplets (or sometimes very small ice crystals). otherwise you wouldn't be able to see them. $\endgroup$ – bon Feb 22 '15 at 21:58
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At the triple-point of a substance, all three phases can be present. Since it takes additional energy to go from ice at 0 C to liquid water at 0 C, there can be a considerable overlap for the two substances, e.g. 1 g ice with 99 g water or 99 g ice with 1 g water, but for thermodynamic equilibrium, the triple point is very narrow.

BTW, the first well-know American chemist, Josiah Willard Gibbs, pioneered in defining the relationship of temperature, pressure and state. See Gibbs' phase rule for more information.

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Unless you're at water's triple point (273.16 K, and a vapor pressure of 611.73 Pa), you must have fewer than three phases if all phases are in equilibrium.

However, it's easy to have ice, water, and water vapor present simultaneously under other conditions if the phases are not all in equilibrium with each other.

Note: Water has other triple points, but they involve multiple forms of ice.

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