Earth From Space: Tidal Island (by europeanspaceagency)
This image acquired on 3 May 2012 from the Pleiades satellite shows the island of Mont Saint Michel and its surrounding bay in northwest France. Mont Saint Michel was a tidal island, meaning that it was surrounded by water at high tide and only when the waters receded was it reachable by foot. In the late 1800s, the causeway was raised to make it accessible from the mainland at all times. In this image, we can clearly see where the water meets the mud flats, with multiple channels weaving through the mud.
For more information and a higher resolution of this image, please visit: http://www.esa.int/esaEO/SEM3MN2VW3H_index_0.html
Credits: CNES 2012/Astrium Services/Spot Image
Fuente: Flickr / europeanspaceagency
Purple Fluorite Cubes, Mapimi, Durango (by cobalt123)
Purple Fluorite Cubes, Mapimi, Durango - Cobalt blue cubes of fluorite crystals, purple that tends towards blue, from Mina Ojuela in Mapimi, Durango. Shot through the glass display case, the central crystal measures about 3/8” square.
Fuente: Flickr / cobalt
Red Rock Canyon, located 20 miles west of Las Vegas off State Highway 159, is home to some incredible geologic formations. If you hike through the area, you will discover native American Petroglyphs, drawings etched into the rocks by natives living in the area. This photo was taken in January, 2011.
If any of you have wondered where the Commonwealth’s beautiful gray granite curbstones come from, today’s photo is the answer: The ~375 Ma (millions-of-years-old) Chelmsford granite. This aerial photo is of the Fletcher granite quarry in Westford, which has been in operation since the mid 20th century. Quarrying of the Chelmsford, and other granites, in Massachusetts has been occurring since the 1600s, according to various town histories.
What is of particular interest in this photo is how well the Chelmsford granite naturally splits at 90 degree angles— something historic granite workers immediately noticed and have taken advantage of over the centuries . The old quarry worker’s term for this is “Rift and Grain”. In New England, the rift and grain of granites, in many places, is oriented in vertically at 90 degrees to one another: in North-South and East-West striking planes: Very convenient for quarrying dimension stone.
The origin of this rift and grain is even more fascinating, and has been the subject of many academic papers over the years including ones by the famous Richard Jahns, Don Wise, and Terry Engelder. The rift and grain are parallel to regional fracture systems in the granite that occurred in response to tectonic stresses in the geologic past— the orientation of those stresses are different than the present day stress in the continental crust of New England (created by pushing from the spreading Mid-Atlantic Ridge). In order to take full advantage of the older rift and grain, quarry operators have to isolate large blocks of the granite and let them “relax” for a few decades so the present-day crustal stress can be removed from the rock. This minimizes wastage and ensures nice, 90 degree angles when the stone is quarried. Photo credit: Bing Maps. (via Massachusetts Geological Survey)
Sigli and Shambe craters in perspective (by europeanspaceagency)
This computer-generated perspective view was created using data obtained from the High-Resolution Stereo Camera (HRSC) on ESA’s Mars Express. Centred at around 18°S and 329°E, this image has a ground resolution of about 20 m per pixel. Sigli and Shambe dominate this image, which highlights the deep fracturing within the crater walls. The shape of the craters leads scientists to believe they were formed from the same impactor, which fragmented into two pieces just before hitting Mars.
Credits: ESA/DLR/FU Berlin (G. Neukum)
Fuente: Flickr / europeanspaceagency
Satellite radar image from the TerraSAR-X sensor of the summit of Cleveland Volcano showing the summit crater and growth of the lava dome. The summit crater is about 200 meters across. Note that satellite radar images have some inherent topographic distortion due to the manner in which they are collected. Picture Date: August 29, 2011. Credit: Dave Schneider, Zhong Lu, AVO/USGS. (via AVO)