Year: Day to Day Men: February 29
Mediterranean Adventure
The twenty-ninth day of February in 1912 marks the falling of the Piedra Movediza, a balancing rock that was located near the city of Tandil in the Buenos Aires Province of Argentina. A balancing rock, or precarious boulder, is a naturally occurring geological formation that features a large rock of substantial size which is resting on other rocks, glacial fill, or bedrock. No single scientific term for the phenomenon exists.
There are several types of geological features that are included under the term balancing rock: glacial erratic that are transported and deposited by glaciers or ice rafts to their resting place; perched blocks deposited due to glaciers, avalanches or landslides often on a slope or hillside; erosional remnants that are carved from local bedrock through extensive wind, water, or chemical erosion; and
pedestal rock, a single continuous rock form with a very small base and a much larger crown. Although not a true balancing rock, a pedestal rock has the appearance of one. These rocks are now believed to have been formed through years of wind and chemical weathering of its base.
The Piedra Movediza was most likely a deposited boulder; it was situated balanced at the edge of a formation of bedrock. Its weight was approximately three-hundred tons, or 272.2 metric tons, and its pedestal was so thin that the boulder was balanced with the wind. The boulder rocked, imperceptible to the eye, from morning to evening in a extremely slow fashion. Visitors to the site would place bottles under the bottom of the rock only to see them broken later in the day.
The Piedra Movediza fell and broke on the twenty-ninth of February in 1912, some time between five o’clock and six o’clock in the evening. There were no witnesses to the event so the true time and cause of the fall are unknown. Several theories regarding its fall were presented among which were vibrations from a nearby quarry blast, people rocking the stone during the day, and disgruntled quarrymen weary of the tourists. No official reason for the fall, however, was ever issued.
Proposals were made to move the three segments of the broken boulder back to its original site on the hill and cement them into position; however nothing was done, most likely due to the mass of each segment. In 2007, a replica of the Piedra Movediza was placed in the original site, now considered a historical symbol of the city of Tandil. The replica does not move as it is securely fastened to the supporting bedrock. This original bouder site is now named Parque Litico La Movediza (La Movediza Lithic Park).
Balancing rocks are found world-wide on all continents. Among these are Finland’s seven-meter long Kummakivi in Ruokolahti, Zimbawe’s Balancing Rocks, a large-scale formation of igneous rocks perfectly balanced; the nine-meter tall Pinnacle Balanced Rock at the Chiricahua National Monument in Arizona, United States; and the Pena do Equilibrio, a giant granite balancing rock in Ponteareas, Spain.
Insert Image: Photographer Unknown, “The Piedra Movediza”, circa 1890, Vintage Print


























