After nearly a week, the unrest of “Mama” Tungurahua has become evident in the city of Quito, in the form a a thin film of volcanic ash. It’s most visible on cars, not unlike the road salt that covers cars back in Ohio. But this accumulation come comes from the thick haze across the valleys of the Inter Andean region of Ecuador.
Lake Atitlan from San Pedro
I am presently living with my family in Panajachel, on the shores of Lake Atitlan in Guatemala. Lake Atitlan occupies a volcanic caldera that formed in a huge eruption about 80,000 years ago. The lake is about 20 km long, 10 km wide and 300 m deep, so even very simplistic volume calculations indicate a large volume of erupted material draping the surrounding region.
In Walter et al. (2011), Deep Mantle Cycling of Oceanic Crust: Evidence from Diamonds and Their Mineral Inclusions, the authors discuss the unexpected continuation of Earth’s Carbon Cycle into the lower mantle of our planet (54). Walter et al. (2011) were led to this conclusion by examining inclusions, microscopic compounds found in the crystals of the diamonds (54).
This year, August 23, the Central Virginia Seismic Zone released an earthquake due to reverse faulting on a north-northeast striking plane. In 1875, the largest historical shock from this region occurred. Since the 18th century, the Central Virginia Seismic Zone has experienced small to moderate earthquakes.
The 2011 earthquake struck 40 miles northwest of Richmond, Virginia.
Some great images of the southwest to start off the week, courtesy of Dr. David Greene.
“Here are a couple of pictures I took from the window of a Southwest Airlines flight coming into Las Vegas, as I was returning to Ohio at the end of my field season. The yellow-orange rocks in the foreground are Jurassic Aztec Sandstone, and the grey-green vegetated slopes above with the prominent grey stripes are Cambrian limestone of the Bonanza King Fm.
It seems that after Hurricane/Tropical Storm Irene came blasting up the eastern seaboard, the great East Coast earthquake of 2011 has been forgotten. Luckily, we’re still getting images of some of the damage from the M5.8 earthquake – and we’re still experiencing aftershocks from the event (although no where near as powerful).
Longtime Denison employee Lyn Boone (who retired in 2010), sent me some images that her brother sent from Mineral, Virginia, the epicenter of the earthquake.
If you weren’t on the eastern seaboard on August 23, you missed a fairly rare occurrence: an earthquake felt widely up and down the eastern North America. The earthquake itself had an epicenter near Mineral, VA – a location that has seen seismicity in the past. You can find references to earthquakes in the journals of the Jefferson family in Monticello from the 1797 and 1833 – and as recently as 2003, showing that earthquakes are definitely not geologically uncommon.