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)
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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)

Fuente: facebook.com

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)
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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)
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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)

Fuente: avo.alaska.edu

Though less frequent, earthquakes on the East Coast can typically be felt over a much larger area than those with a similar magnitude on the West Coast. The bedrock in California, for example, is fractured, causing seismic waves that travel through it to dissipate faster. In the eastern half of the United States, the bedrock is less fractured and stronger, allowing earthquake energy to travel farther. (via NYTimes)
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Though less frequent, earthquakes on the East Coast can typically be felt over a much larger area than those with a similar magnitude on the West Coast. The bedrock in California, for example, is fractured, causing seismic waves that travel through it to dissipate faster. In the eastern half of the United States, the bedrock is less fractured and stronger, allowing earthquake energy to travel farther. (via NYTimes)

Fuente: The New York Times

This was the view out the International Space Station’s cupola on Jan. 1, 2013, around 09:37 UTC, looking nearly straight down the gullet of Italy’s Mt. Vesuvius. Perhaps you’ve heard of it? Just a little more than 1,900 years ago, it blew its top in the most famous volcanic eruption in recorded history. About 16,000 people lost their lives that day due to pyroclastic flow—searing hot ash blasting outward from the stratovolcano’s maw. The volcano has erupted many times since then, including in the 20th century. Got that? It’s still active. Now take another look at that photo, and let the volcano’s surroundings settle in to your mind. It sits just a few kilometers from Naples, and more than half a million people live in the volcano’s red zone—where destruction from a big eruption would be swift and brutal. That’s why volcanologists consider it the world’s most dangerous volcano. Given all we’ve learned about volcanoes in the past few decades, I hope scientists would be able to give people a few days’ warning about an eruption. Science, after all, saves lives. (via Bad Astronomy)
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This was the view out the International Space Station’s cupola on Jan. 1, 2013, around 09:37 UTC, looking nearly straight down the gullet of Italy’s Mt. Vesuvius. Perhaps you’ve heard of it? Just a little more than 1,900 years ago, it blew its top in the most famous volcanic eruption in recorded history. About 16,000 people lost their lives that day due to pyroclastic flow—searing hot ash blasting outward from the stratovolcano’s maw.

The volcano has erupted many times since then, including in the 20th century. Got that? It’s still active. Now take another look at that photo, and let the volcano’s surroundings settle in to your mind. It sits just a few kilometers from Naples, and more than half a million people live in the volcano’s red zone—where destruction from a big eruption would be swift and brutal.

That’s why volcanologists consider it the world’s most dangerous volcano. Given all we’ve learned about volcanoes in the past few decades, I hope scientists would be able to give people a few days’ warning about an eruption. Science, after all, saves lives. (via Bad Astronomy)

Fuente: Slate

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