Earth’s Living Thermal Iris
**The striking color zonation of this hydrothermal feature** highlights a delicate balance of water temperature gradients and extremophilic biology. Deep within the central vent of the spring, exceptionally hot water remains clear and absorbs longer red wavelengths of light, scattering a brilliant blue-green color back to the surface. As the water discharges outward across the shallow siliceous sinter terraces, it cools progressively, giving rise to concentric rings of distinct microbial mats. These outer yellow, orange, and reddish borders are composed of dense communities of thermophilic bacteria and archaea, such as *Phormidium* and *Synechococcus*, which utilize specialized pigments to thrive in conditions toxic to most life forms.
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