Geological air conditioning
The Jangsu Stone-Formed Stream Ice appears as a vast, sloping field of boulders at the base of a mountain. This landform is a talus slope, composed of angular fragments of granite and gneiss fractured from the surrounding cliffs by ice wedging over millennia. While the area seems ordinary, the air emerging from the gaps between the rocks is unnaturally cold, even on the hottest summer days. This phenomenon is a result of a process known as the chimney effect, or Balch ventilation.
During winter, cold, dense air sinks deep into the porous rock pile, displacing the warmer, lighter air which rises and exits from the top of the slope. The thick layer of insulating rock traps this mass of frigid air through spring and into summer. As ambient temperatures rise, this subterranean reservoir of cold air remains. Groundwater seeping through the talus slope freezes on contact with the chilled rocks, forming lenses of interstitial ice that can persist until August. The greater the temperature difference between the trapped air and the summer heat, the stronger the convective airflow, paradoxically causing ice to form even as outside temperatures exceed 30°C.