Geologists run on coffee. Its fuel better then any fossil fuel
for getting out of bed in the morning. Just ask the Beloit College Geology
Department. Its Web site proudly announces: "Coffee: The life blood of
the geology department. Coffee maker: The life regulator of the Geology Department."
When students declare that they are going to major in geology at Beloit, they
receive a personalized coffee mug. When a geology major graduates, the year
is painted on the bottom, and the mug itself is archived for future return visits.
Many geologists lug a thermos of coffee with them in the field. Others make
it themselves on the spot. Small, single-serving French presses make this easier
and tastier than it used to be, but the rituals of having a "coffee
break" to review data, check the maps and consider the next steps can be
an important element of field work.
When we were doing field work in the Swedish Lapland, Dallas and I learned that
our Scandinavian colleagues required official coffee breaks in the morning and
afternoon: Everything stopped while we boiled water, fixed the coffee from scratch
and drank it. Only then could the field work continue.
Coffee as an earth material
Coffee not only fuels geologists, it also fuels the educational process of
teaching major concepts in geology. Coffee can be treated as an earth material.
Its a favorite substance, for example, to illustrate angle of repose,
including the relationship between size of the grains (the phi of the title)
and slope angle. Generations of students have learned about the differences
between angles of repose for finely ground coffee, coarsely ground coffee and
whole beans. A masters thesis at the University of Georgia focused on
determining "the effect of moisture content on angle of internal friction
and angle of repose of coffee beans." Its a great material for modeling.
Preparing coffee is all about leaching, which is a critical topic in hydrologic
discussions. Whether the process is filtering, percolating or pressing, the
leaching process applies. Water percolating through coffee grounds can model
the origin of many features in caves and karst regions.
Back in the old days, making coffee in the field meant using a container of
cheap instant coffee. When geologists carried this coffee during work at high
elevations, the unwary learned what pressure differential really means. A jar
that was sealed at low elevation and opened at 10,000 feet offered a graphic
lesson to those who failed to heed the warning to stick an ice pick in the lid
before opening the jar. The positive pressure in the jar blew out the instant
coffee as soon as the seal was broken, usually in the face of the person opening
it. The phrase "raccoon eyes" comes to mind as a description of the
result.
What we still dont know
Recent research into the behavior of materials has helped us understand how
much we still dont know about a material as familiar as coffee. Just think
about the transition that a "brick" of coffee undergoes when the seal
is broken. In a vacuum-packed bag, the irregular coffee grains are pressed together,
closely interlocking their jagged edges and creating a rigid block. When the
pressure is released after opening the bag, the coffee grains flow easily.
Yet physicists dont understand the theory enough to tell Starbucks, Peets
or Caribou Coffee exactly how rigid a bag of vacuum-packed coffee should be.
Nor can they predict the exact moment at which the ground coffee will turn from
a solid to powder.
The complexities of coffee-grain behavior seem to be a function of the interaction
of the individual beans or grounds, which creates a system that is extremely
difficult to model. A single bag of coffee produces enough granular interactions
to swamp a supercomputer.
Examples of granular flows on Earth include dune formation and migration, as
well as avalanches of rock and granular snow. Images from the surfaces of other
planetary bodies such as the moon and Mars indicate landforms
that were created by granular flow.
One way to simplify granular flow processes, as a way to understand the system
and predict its behavior, is to eliminate some of the variables. Gravity, for
example, can be removed from the equation through experiments in space. A series
of experiments on "mechanics of granular materials" (MGM) were included
on space shuttle missions STS-79 and STS-89.
An MGM experiment was also part of the science package on STS-107, the final
flight of Columbia. The experiment studied the behavior of saturated sand when
exposed to confining pressure; some of the goals were to learn more about how
to strengthen building foundations against earthquakes and to better understand
how vibrations affect grains of soil and sand. The MGM project scientists have
estimated that, with careful analysis of data returned during the Columbia mission,
they have achieved 50 to 60 percent of the scientific goals of this experiment.
Similar experiments are planned for the International Space Station in 2007.
James Jenkins, a physics professor at Cornell University, studies granular materials
for NASA. In an interview with NASA Science News (Dec. 4, 2002), he noted some
of the economic value of understanding such a process: "Flows of granular
materials that resemble avalanches are important in coal-fired power plants,
in the manufacture of pharmaceuticals, in the processing of aluminum, and in
the production of plastics from pellets. Its hard to think of an industry
that does not employ a granular flow during some processing operation."
And as the coffee flows, so too do the geologic ideas. Learning more about the
behavior of coffee can help us make sense of a wide range of behaviors of other
earth materials. In addition, this knowledge will help us understand more about
other material behavior as well, including everything from breakfast cereal
being poured into a bowl to the balls that generate winning lottery numbers.
Right now, Im staring into my coffee cup looking for a little inspiration.
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