Examples of heliotropism are easily observed in the microbially produced stromatolitic columnar growths in the thermal effluents from geysers and hot springs at Yellowstone National Park, Wyo. Six effluent regions with microbial mats that produce centimeter-sized conical to columnar structures have been analyzed. The columns or cones tilt south at up to 30° zenith angles, independent of water flow direction (velocities up to 8 cm/s). Subsurface layers and shallow cores of siliceous sinter, presumably microbially produced, also appear to preserve evidence of earlier heliotropism. In combination with similar discoveries in living stromatolitic structures at Shark Bay, Western Australia, this evidence provides a foundation upon which a methodology can be developed for using selected ancient stromatolites to deduce paleo-latitude, paleo-obliquity of the ecliptic, paleo-days per month and year (by using laminae counts), paleo—spin axis north-south, paleolocation of the geomagnetic pole (using paleomagnetism), and other paleoearth and earth-sun-moon dynamics.