August 21 - On & Off Earth
August marks the tenth anniversary of an Earth event that changed our quiet Louisa world suddenly and dramatically. Everyone here remembers exactly where they were at 1:51pm on August 23, 2011 as a magnitude 5.8 earthquake, literally, rocked that world. The quake, felt by tens of millions of people up and down the entire eastern seaboard, is now known as the Mineral earthquake and while the aftershocks have, mostly, subsided, the memories have not.
In fact, over these last ten years I have yet to speak to anyone that was on the east coast that day that didn’t want to share their memory of the event; seems when the ground under your feet shakes violently, a lifelong memory is created.
Several factors combined to make our quake unusual and our Central Virginia Seismic Zone still an area of interest and study for geologists. Most big earthquakes, and 5.8 is big, occur at a boundary zone where two massive chunks (plates) of Earth’s thin, solid crust are separating, colliding or slipping past each other. We are not in a boundary zone today but we were 200+ million years ago and remnants of that history linger.
Also, unlike the shaky west coast, an active boundary with young broken rock that doesn’t transmit earthquake energy very far, the fairly continuous bands of stacked and tilted rock below Louisa stretch the length of the east coast and the rock is old, cold and dense. That allowed the earthquake waves to travel much farther and be felt by so many, from Canada to Georgia.
Ten years later, the Washington Monument has been repaired, Louisa has a new high and elementary school but traces of quake damage are still visible (certainly in my neighborhood) and much research continues; how often do quakes this big occur, decades or centuries apart? How prepared is the East coast for the next big shake? As I mentioned in my very first column after a little aftershock, the question remains, when will the next quake occur? No one knows but we likely will all remember that one, too.
August sees the much faster Earth, catch back up with both Saturn and Jupiter, leaving the gas giant planets in the evening sky all night long. They will form a line with the Full Sturgeon Moon on the 22nd (Jupiter the brightest and closest to the moon). This full moon fits the original definition of a Blue Moon, the third of four full moons in one season. Back in 1946, a writer in Sky & Telescope magazine erroneously called the second full moon of a month a Blue moon and that easier to understand and remember definition stuck.
Venus remains low but brilliant as the Evening star in the west after sunset. A thin crescent moon sits near the planet in the sky on the 10th. The next night is the very reliable Perseid Meteor Shower; bug spray and a lounge chair all you need to watch for “shooting stars”. Our nearby, actual, star appears to move from Cancer into Leo on the 12th.
One of my goals for this column is to get readers outside to enjoy our world; August makes that tough. You realize quickly stepping into the dank August air, Earth is in charge and you are part of the food web and on the menu, a host of critters quick to buzz near a wandering human looking for dinner. I hope you still get out daily but do recommend bug spray, a broad brimmed hat and keep moving, Today On Earth..
Next month, an even bigger 20th anniversary, that we all, sadly, will also remember forever.
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