Azul Odd Rock

October 08, 2010

Photographer: Luis Argerich; Declan G. De Paor
Summary Author: Luis Argerich; Jim Foster

October 2010 Earth Science Picture of the Day Viewer's ChoiceThe egg-shaped rock shown above was found in what is referred to as the Azul Sierras of the Buenos Aires Province in Argentina. It stands approximately 15 feet (about 5 m) high and is about 30 feet (9 m) wide. This range is part of the ancient Tandilia Mountain System that begins near Olavarria, Argentina and descends eastward into the Atlantic Ocean between Mar del Plata and Miramar -- two popular coastal cities in northeastern Argentina. The Tandilia system contains some of the oldest rock formations on Earth, dating from the Precambrian period. Tens of millions of years ago, this system was part of a cordillera that was higher than the Himalayas. Today, however, the highest peak is just 1,804 feet (550 m) high. How this particular rock acquired its shape and how it was placed in its current position is a mystery. However, the formerly surrounding rock has been eroded away mechanically over the eons due to repeated heating and cooling of the rock surface. Photo taken on September 11, 2010.