Wednesday, January 26, 2011

How to Make Coffee Strandlines or Rhythmites

Once upon a time, MOH and I left suddenly for an unexpected trip of unknown time duration, and I failed to empty all the coffee cups. Upon arriving back, having been gone most of 14 days, I tentatively looked in my cup expecting to find terrible mold, instead finding these lines of coffee deposited around the side of the cup.

"Varves!" I exclaimed, "Except they aren't from yearly deposits, they're from daily deposits!"

I've reflected a little, and asked a few close-at-hand sources, and decided these aren't really varves — and they probably aren't really rhythmites, either — for the simple reason that varves and rhythmites would be layers, of concentrated coffee in this case, that would have been deposited in the bottom of the cup. Instead, these must be more akin to strandlines — or shorelines around a coffee lake, in this case — as suggested by @GeoTheoBO. Other suggestions for what to call these deposits were Stratified Caffineite (@CGKings317), rhythmites (@alexbirtwisle), and my favorite, "Jarves" from "Java-varves" (@Dhunterauthor). Everyone else is welcome to jump into this discussion and naming exercise in the comments.
Prior to deciding that these were really the results of daily evaporation of coffee, I did count the rings. There are 13, with a possible incipient 14th one near the bottom representing the partial 14th day during which we arrived back in time to check the cup. The lines I've drawn above are based not just on the locally fuzzy record shown in that one photo, but on the three photos I took documenting the entire stratigraphic record around the entire inner part of the cup.
Here are the final determinations. A few of the days are a little fuzzy and the lines have been brought in from the side, just like you might have to do when correlating deposits out in the field. Most day's deposits are light toward the bottom and darken upward, possibly reflecting something having to do with diurnal temperature and humidity variations. To be honest, I don't really know when the darkest portion of each day's ring forms, whether at night, during the day, or at some other time. The cup was sitting on the kitchen counter in the sunlight of the window the entire time we were gone; evaporation would presumably have been strongest during the daylight hours, possibly resulting in the lower, lighter colored part of the layer. Any other thoughts?

This post has been submitted to the Bake-Sale Accretionary Wedge (AW#30), though no baking was involved.

UPDATE: Accretionary Wedge #30: the Bake Sale is now up at Mountain Beltway. It's a very yummy Wedge, I might add.

10 comments:

Maitri said...

Reminds me of the floodlines in New Orleans after the water receded in stages.

Nina F said...

Your post is indeed an interesting study in jarvochronology!

Cujo359 said...

I think if you put milk in your coffee you'd have had more of a biological experiment.

Was this trip during the summer, or do you have a thermostat with a day/night cycle? Either might account for the daily variation in the rate of evaporation.

Silver Fox said...

Maitri, we'll add floodlines to the possible list of names - kind of like bathtub rings, also (except possibly nicer looking).

Silver Fox said...

Nina, I love your term, "jarvochronology! And I hope you don't mind that I added your comment. Not sure why that wasn't working for you. If Google doesn't have you signed in properly, you could try Name/URL. And if Captcha isn't working, I haven't the vaguest idea how to deal with that!

Silver Fox said...

Cujo, the trip was in mid-September, the days were probably warmish with cool nights, humidity was probably invariably low to mediocre. I suspect the heat from the sun through the window did the trick!

And I was quite glad it wasn't a biogeo experiment.

Gaelyn said...

A very interesting unplanned experiment leaving a wonderful javafacation.

Cath@VWXYNot? said...

Awesome!

My tea mug (containing strong black tea with a little milk) looks a bit like this right now, although with much fainter colouration, despite being cleaned this morning. I tend to leave it sitting for a while before taking a big glug or two, so the rings are a good marker of how fast I drink tea across a temperature range from just below boiling to barely warm.

Silver Fox said...

Javafication - another great word! :)

Silver Fox said...

Thanks, Cath. Haven't tried this with tea, I think they could be more permanent, even if lighter colored.