April 19, 2012

Geology Word of the Week: T is for Time

Posted by Evelyn Mervine

Layers of travertine deposition in the Sultanate of Oman, January 2009.

def. Time:

1. What the clock (or the cesium atom) measures.

2. “The indefinite continued progress of existence and events in the past, present, and future regarded as a whole.” (From Google Dictionary).

3. “A finite extent or stretch of continued existence, as the interval separating two successive events or actions, or the period during which an action, condition, or state continues; a finite portion of time; a period.” (From the Oxford English Dictionary).

4. One of four dimensions in the spacetime continuum.

I have not written a geology word of the week post for 5 months– about 150 days. My last geology word was S is for Syncline back in November. On a blogging timescale, 5 months is an eternity. In fact, a lack of posting for five months is what Ron Schott uses to classify a blog as “dormant” on his Geoblogosphere list. However, on a geologic timescale 5 months is no time at all. The Earth is 4.54 billion years old, and most geologists think on timescales of thousands or millions or even billions of years.  To humans, of course, with our paltry lifespan of a hundred years or less, 5 months is a significant amount of time. Months, days, hours, and even seconds are important on human timescales.

However, geologists often use geologic time to put human events in perspective. For example, I’ve taken not quite six years to complete my PhD in geology. In my graduate program six year PhDs are common. When you’re struggling along through graduate school, six years seems like an eternity sometimes. To help relieve the stress, the geology graduate students joke with each other, “Well, on a geologic timescale, of course, this is nothing. Heck, I could take 10 years to complete my PhD and it would still be nothing, geologically speaking.” And then there’s the old stand-by joke: Never loan geologists money… because they’ll pay you back on a geologic timescale.

A geologic timescale "clock", putting human existence into geologic perspective. Image credit: Wikipedia user Hardwigg. Image taken from here:http://en.wikipedia.org/wiki/File:Geologic_Clock_with_events_and_periods.svg

For those of you who are not familiar, under normal blog conditions I muse about a geology word every week here on Georneys. I first give a definition of the word, and then I explain a little about the importance of the word in geology. I often present a compilation of pictures that illustrate the geology word in action. For example, there were some impressive picture compilations in X is for Xenolith and M is for Migmatite. Pictures are often provided by Geoblogosphere members, by my geology colleagues, and by my twitter followers and blog readers. Geology words are also often proposed by my blog readers and twitter followers, so in a way the geology word of the week is a group effort, and I am merely the editor of an ongoing geologic encyclopedia.

Because humans like patterns and I need some way to focus a very, very long list of geologic words (scientists like words, and geologists are no exception), for my weekly words I work through the alphabet in order. Since the last geology word started with an S, that means this week’s word starts with a T. Next week’s word will begin with a U (feel free to start thinking of suggestions), and in two weeks the word will start with a V, and so on.

From November 2010 (when I started writing Georneys) to October 2011, I was rigorous about posting a geology word every week. However, last October I started to become somewhat busy. I put the geology word of the week on hold for a few weeks to prepare for my wedding at the end of October. I managed to post S is for Syncline in November, but after that I found that I simply didn’t have enough time for the weekly word. I consider blogging a fun (and important) hobby, but in the last few months of my PhD thesis writing, I didn’t have time for any hobbies… or for as much exercise, proper eating, or restful sleeping as I would have liked.  Now that the thesis defense is over, I am bringing back the weekly geology word. Depending on travel and other circumstances, there may be a few weeks where I miss a word. However, I’ll do my best to post a word every week. You can help me with that by suggesting words as well as by providing information and pictures for the selected weekly words. I can often be bribed to write about a certain word if someone provides good pictures.  As I mentioned above, the geology word of the week really is a team effort.

Although I considered other T words such as tafoni and tektite and tourmaline, after some musing I eventually decided that “time” is a fitting word for the resurrection of The Geology Word of the Week. Time seems an appropriate word because significant time has passed (on a human timescale, anyway) since I last posted a geology word. Also, I have spent much of the last few months thinking about time. Indeed, my PhD thesis even contains the word time. The title of my thesis is: Determining timescales of natural carbonation of Peridotite in the Samail ophiolite, Sultanate of Oman. My PhD is technically in Marine Geology, but if I were to describe my expertise in geology, I would probably describe myself as a geochronologist and geochemist who enjoys using isotopes and other geochemical tools to constrain ages of rocks and rates for various geologic processes.

Time is an interesting concept. Humans intuitively understand time, at least on a certain level. We fundamentally understand time and the passage of time through natural events which take time– the rising and setting of the sun, the rising and falling of the tides, the passage of patterns of stars in the sky, the waxing and waning of the moon. Long ago, time was measured by observing various periodic natural phenomena (such as the waxing and waning of the moon) as well as through use of devices such as sun dials and hourglasses filled with sand. Today, we primarily measure time with various mechanical and electronic devices. However, we also precisely define time and calibrate our artificial clocks by using atomic clocks. The official SI unit of a second is defined as “9,192,631,770 cycles of that radiation which corresponds to the transition between two electron spin energy levels of the ground state of the 133Cs atom.” (from Wikipedia’s article on Time). So, although we now wear various mechanical watches, we still base our understanding of time on the observation of periodic natural phenomena.

Time is a very important concept in geology. Understanding when and how quickly and in what order various geologic events and processes occur is key in understanding how our planet– and other planets– operate. Geologic time began as a relative concept– figuring out the order in which geologic layers were deposited, noting when certain fossil organisms lived and died, determining the order in which minerals crystallize and erode. The discovery of radioactivity in the late 1800s and the development of absolute geologic dating techniques in the 1900s (and continuing to today)  revolutionized geology by providing absolute dates and rates for geologic events and processes. Geologists were able to determine the age of the Earth and to add dates to the previously-established (in a relative sense) geologic timescale.

The determination of geologic ages and rates continues to be very important for geologic research. As an example, in my PhD research I worked to better constrain rates of carbonate formation and erosion in the peridotite layer of the Samail ophiolite. Understanding timescales of peridotite carbonation is important because such carbonation represents a natural sink in the carbon cycle. Also, enhanced carbonation of peridotite is one proposed method for carbon sequestration that could offset anthropogenic emissions of carbon dioxide to the atmosphere. However, before scientists can figure out how much we have to speed up natural carbonation of peridotite to offset anthropogenic emissions, they first have to know how quickly peridotite carbonation occurs naturally.

The latest (2009) Geologic Timescale from the Geologic Society of America. A downloadable PDF of the timescale can be found here: http://www.geosociety.org/science/timescale/.

I think about time and use the word time all the time (Example A). Time is an important term for geologists– and scientists in general– to understand and define carefully. I have a good understanding of time in my daily life and also of geologic time. However, when I think more deeply about time– for example, thinking about time as one of the four dimensions of spacetime– I wonder if I really understand time at all. I may have to read up on some theoretical physics and time now that I have a little extra time.

Certainly, there is a part of me that feels amazed that– finally– the time has passed, and I have defended my PhD. Along the way, I felt that my PhD research and progress crept along slow as molasses. Then– all of a sudden– I was ready to defend. Now, I look back and wonder where the time has gone.

About a month ago, I remember being in a state of high-stress and sleep deprivation and panic, wondering how I would survive the next few weeks. And I remember thinking back on other high-stress and important events– my competition in the Junior Olympics as a kayaker, my advanced placement examinations in high school, the SAT, the college admissions process, finals in college, the GRE, the graduate school admissions process, every single math test I took at MIT, my PhD qualifying exams, my wedding, and so on. Months of anticipation and worry and stress preceded each of these events. And yet, time passed, and I survived each event– thrived even, with some– and then afterwards I felt a strange sense of wonder: Was the event truly over? Had I truly survived? Was there nothing more to anticipate? How had the time passed? What now? Along with the wonder, I felt a surreal sense of calm, a satisfied sense of accomplishment. I would relax for awhile, returning to a more normal, less-stressed state. And then, after awhile, I would start anticipating the next event.

The anticipation of my PhD defense was more challenging, by far, than any of the previous important events mentioned in the list above. When I felt overly concerned over the last six months or so, I just took a deep breath and reminded myself of all those other difficult events. Time will pass, I told myself. Time will pass.

Well, time did pass. And I survived– thrived even– during my PhD defense. And now I feel that same surreal sense of wonder and calm. And now I find myself musing over time, for a time at least.