Batholith Face Exposed
June 02, 2010
Much of the Earth’s continental crust is granite, a hard plutonic rock consisting of quartz, feldspar, and accessory minerals such as biotite or hornblende. It usually forms as large, deep, slowly cooling intrusions, or batholiths. Each formation is unique; varied cooling rates and mineral contents explaining differing crystal size, color and hardness. The highlands around the Boston basin are replete with granite intrusions. Nineteenth-century American builders became connoisseurs of Massachusetts granites. Quincy, a seaport town south of Boston, was known as the "Granite City" because of the hard, dark, course granites underlying its hills. Its batholiths supported a thriving granite industry for over 100 years. Granitic building materials from Quincy were shipped all over the world. In more recent years, debris from another amazing Boston-area engineering project, the Big Dig, was used to fill many Quincy quarries back to ground level, leaving only portions of the batholiths tops exposed. Some of these exposed granite faces, previously adorned with dusty quarrymen dangling hundreds of feet above the quarry floor, are now festooned with artwork created by rock-climbers suspended tens of feet above vegetated Big Dig debris. This photo shows the face of the upper portion of a granite intrusion that previously formed one wall of the Granite Rail Quarry. An unstable climber at bottom-right provides scale. Note the exposed joints and parallel vertical fracture planes characteristic of granite. Photo taken on May 2, 2010.
Camera Maker: Canon; Camera Model: Canon PowerShot SD1000; Image Date: 2010:05:02 14:22:26; Focal Length: 12.1mm; Aperture: f/11.0; Exposure Time: 0.0080 s (1/125); ISO equiv: 80; Exposure Bias: none; Metering Mode: Matrix; White Balance: Auto; Flash Fired: No (Auto); Color Space: sRGB.