Friday, March 5, 2021

Drunk on Seismology - Tectonic Event Imperial IPA


My next Drunk on Geology is for the Tectonic Event Imperial IPA by Great Basin Brewing Company, makers of the also geologically themed beer Ichthyosaur "Icky" IPA.

What is a "Tectonic Event"? Lets look at some of the definitions of the words to get a better feel for the usage of those terms.

"A branch of geology dealing with the broad architecture of the outer part of the earth, that is, the major structural or deformational features and their relations, origin, and historical evolution."
"A non-committal term for any incident of probable tectonic significance that is suggested by geologic evidence but whose full implications are unknown. Seismic Event."
Seismic Event:
"An earthquake of a somewhat similar transient earth motion caused by an explosion."

Definitions courtesy of the Dictionary of Geological Terms, 3rd Ed. 

So clearly the usage of the term "Tectonic Event" is meant to illustrate an earthquake. Tectonic, specifically Plate Tectonics, is the study of the earth's crust as it is broken up into individual plates. These individual plates move around, slide past each other, move over and under each other, and pull away from each other. Where one plate come in contact with other plates, where these motions occur, this is where the "tectonic events" occur. This is the source of earthquakes, generally.

Plate Tectonic map of the earth. Image courtesy of the NPS

When looking at the plate boundaries in the map above and comparing them to the earthquake locations in the map below, you can see a strong similarity to the locations of these events. And in actuality, the locations of the earthquakes on maps, such as the one below, helped scientists to draw the plate boundaries on the one above. 

Map indicating the locations of earthquakes across the globe. Image courtesy of the NSF.

The plate boundaries are made up of faults. Faults are breaks, or fractures, in the the rocks and they don't just occur at plate boundaries, however the pressures that move the plates are more readily present at the plate boundaries. Earthquakes occur at these plate boundaries because as the plates move past each other the slippage isn't usually smooth.  They get stuck due to friction. However, the pressure that pushes the plates continues. So that pressure builds up over time. The longer the plates are not able to move past each other the more pressure builds up, until the friction holding the plates in place breaks and the plates have a sudden movement. This movement releases the pressure, and the energy, that had built up along the fault. The energy then radiates outwards from the fault slippage, producing the ground shaking known as an earthquake. It is this slippage that would be termed the "Tectonic Event".

Text from the side of the bottle:
"This West Coast-style IIPA features seismically bold flavors with epic momentum and magnitude. A delightfully clean malt profile gives way to powerful quakes of Columbus, Chinook, Citra, Centennial, and Amarillo hops."
One of the ways that seismologists record and study earthquakes are by studying the energy that is released during these tectonic events. This energy is recorded by a machine known as a seismograph, recording a sheet of squiggly lines known as a seismogram. 

An illustration of a seismogram

As the ground shakes, the seismograph records that shaking on a piece of paper (or digitally). Originally this was recorded by simply a pen that would remain free of the earth's motions while the paper would move around beneath it, creating these jagged lines that eventually smoothed out. This image of a seismograph is what is represented on the front of the bottle, surrounding the hops illustration. These graphs, combined with other seismograms from around the world, can be used to identify the exact location of the earthquake, how big the earthquake was (magnitude), and how much energy was released when the fault slipped. 

"Rock your palate to its core"

The reason that the Great Basin Brewing Company chose to honor the tectonic event as one of their logos is likely due to the very seismically active area that their brewery in Reno, Nevada sits within, the Great Basin. 

Map of the Great Basin, showing the north-south trending mountain ranges. Image courtesy of Wikipedia

The Great Basin is an area of the US that is experiencing expansion, kind of like a sponge that had been squeezed and then was let go. As the plate expands, the faults along the Great Basin periodically move because of the stresses placed on the plate due to this expansion. The expansion had produced the topography that can be seen in the image above. This area is covered with north-south trending mountain ranges, which all align with north-south trending fault lines. As the basin continues to expand, periodically these stresses from the expansion will produce earthquakes from the slippage along those faults all over the Great Basin region, including Reno, Nevada, which lies along the western edge of the basin.

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