Why does hot water turn into steam in a flash tank?

In flash steam geothermal power plants, high-temperature water is extracted from deep underground under high pressure. When this pressurized water is drawn into a container at the surface known as a flash tank, it experiences a sudden decrease in pressure.1

According to the principles of physics, the boiling point of a liquid is the temperature at which its vapor pressure equals the surrounding pressure. Because the boiling point of water decreases as the ambient pressure drops, the sudden reduction in pressure within the flash tank causes the water to reach its boiling point instantly. This rapid change forces the liquid water to "flash," or vaporize, into steam, which is then directed to drive a turbine for electricity generation.312