Calendar: February 29

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

Calendar: January 17

Year: Day to Day Men: January 17

A Sunny Day

The seventeenth of January in the year 1761 marks the birth date of Sir James Hall of Dunglass, 4th Baronet, who was a Scottish geologist and geophysicist. He was the first to use an analogue modeling synthesizer to investigate the formation of folds in the earth’s layers. Hall’s discoveries in this field were published in 1815.

Born at Dunglass Castle in East Lothian, James Hall was the only son and heir of Sir John Hall, 3rd Baronet who had served on the Grand Jury for the 1748 Edinburgh trial of those involved in the 1745 Jacobite uprising. James Hall studied at Christ’s College, Cambridge, and the University of Edinburgh during the 1780s. At Edinburgh, he studied under Professor of Medicine and Chemistry Joseph Black and Regius Professor of Natural History John Walker, one of the main scientific consultants of his day.

From attending Walker’s courses, Hall learned how to use the chemical compositions of minerals to determine the relative age of the earth’s layers. Walker also emphasized in his classes the importance of chemistry to the study of geology. After his studies, Hall travelled Europe to seek book dealers who dealt in works on mineralogy, geology and chemistry. His travels to France brought him into contact with nobleman and chemist Antoine-Laurant de Lavoisier who wrote the first extensive list of elements. Lavoisier was also instrumental in the development of the metric system as well as the reformation of chemical nomenclature through a set of rules for the generation of systematic names.

Upon his return to his home in Scotland, Sir James Hall continued his studies in the fields of chemistry and geology. During the 1780s and 1790s, he was interested in geologist James Hutton’s ‘Theory of the Earth” which suggested that the strata of the planet was continually being worn or melted down, thus making the planet a giant system of circulating material. Hall traveled with Hutton and professor John Playfair in the spring of 1788 on a boat trip to Siccar Point on Scotland’s Berwickshire coast. At Siccar Point, they discovered a rock formation that became known as Hutton’s Unconformity. This geological phenomenon marked the location where rock formations, created at different times and by different forces, joined together. Other locations in Scotland were later identified by Hutton.

Initially skeptical of the chemical viability of Hutton’s theory, Hall soon published several papers on the chemical composition of the strata. He experimented on granite to prove that it was possible for molten rock to form a continuous sequence of deposits, typically in parallel layers. By melting basalt in an iron furnace, Hall demonstrated its return to the original form when cooled; his melted limestone proved that, melted under pressure, limestone did not decompose. These findings were published by Hall in the Royal Society of Edinburgh’s scientific journal “Transactions”.

Sir John Hall traveled throughout Europe to examine the geological formations of Mount Etna and the Alps mountain range, both areas formed from the collision of the planet’s tectonic plates. He also studied the similarity of lava flows in Italy to geological sites in Scotland. Hall, in addition to his works in the field of science, was also the author of various works on architecture among which was his 1797 “Essay on the Origins and Principles of Gothic Architecture”. Sir John Hall, 4th Baronet, died at home in the central area of Edinburgh survived by a wife and six children. He is buried in Greyfriars Kirkyard in central Edinburgh.

Anak Krakatau

Anak Krakatau

Anak Krakatau has grown at an average rate of five inches (13 cm) per week since the 1950s. This equates to an average growth of 6.8 meters per year. The island is still active, with its most recent eruptive episode having begun in 1994. Quiet periods of a few days have alternated with almost continuous Strombolian eruptions since then.

Hot gases, rocks, and lava were released in an eruption in April 2008. Scientists monitoring the volcano have warned people to stay out of a 3 km zone around the island. Several videos of Krakatoa on YouTube show recent footage of eruptions and of the inside of the crater as seen from the rim of the volcano.

On 6 May 2009 the Volcanological Survey of Indonesia raised the eruption alert status of Anak Krakatau to Level III. A Level Three alert signifies an increasing tendency toward eruption, relatively high unrest, and magna close to the crater. A recent expedition to the volcano has revealed that a 100-meter (328-foot)-wide lava dome is growing in its crater. The dome has two active vents that eject incandescent gas.