Intriguing distractions

One of the things I have been reading in the process of learning the things I need to know for my new job is the book "Description of regional geological and geophysical maps of the Skellefte District and surrounding areas" A comment in the introduction caught my eye "Application of geophysical methods in metal exploration started more than three centuries ago in Sweden. Magnetic methods were in use as early as 1640.".

Sadly, the paragraph did not list a source for this information. However I see that one of the editors of the book is my boss, so I have emailed him to ask if he happens to know of the source. I did see a couple of books from the 1800's cited in the bibliography, so perhaps one of them could be the source. It looks like our library might have them, but they are in Swedish. While my language learning has gotten good enough to easily read children's books and books that I have read before in English, I fear that I am not up to trying to track down obscure references to magnetic methods which were in use in the 1640's. So instead I will make note of it here—perhaps next year I will be fluent enough to chase up that information, if my boss doesn't have a useful reply (he is traveling now—he has been at a conference all week).

Ok, back to real work, the clock is ticking…

first day of IMA2010

Today is the first full day of lectures at the International Mineral Association’s 2010 Congress in Budapest. I spent the morning attending lectures on the topic of History. The first talk of the day was _The tradition of Theoprastus’ “On Stones” during the early stages of modern mineral science_ by A. Mottana.

He spoke on the ancient text written by Theoprastus usually called “De Lapidibus”, or “On Stones”, which was written around 313-305 BC. Its arrival to Italy in 1427, brought from Constantinople to Florence by Trancaso Filefo, was one of the important parts of the resurgence/rediscovery of ancient learning in the Renaissance, being the first entire book written on stones and minerals. The source of the document that arrived in Italy in 1427 is thought to have been the Vaticanus graecus 1302, a codex written in Byzantium c. 1300-30.

The lecture opened with a definition of the period of the Renassiance, which started in Italy in 1392 when Manuel Chrysoliora was appointed to teach Greek Language & Literature at the University in Florence, and ended in 1611 when Johannes Keppler published Strena Seu de Nive Sexangula, which was the first mathematical text on crystal structure, and thus an important start to the age of science. From there he touched on the various Renaissance scholars who used this source in their own work, and who did translations, and when. The talk was fascinating, but due to the format (only 20 minutes available) it was necessary for him to hurry over the latter portion of the talk, and my note-taking didn’t keep up. (Any errors in the above are due to my rusty note-taking skills, and not to the speaker).

My host’s great-grand father

When I was in Norway earlier this summer, rather than staying in hotels I chose to couch surf, for much of the trip. There is something quite nice about staying with local hosts; one gets to meet people one wouldn’t have otherwise met, and one gets to learn something about the local area and the people who live there. Or, in some cases, the people who have lived there long ago.

My host in Bergen, when she discovered that I’m a geologist told me about her great-grandfather, who was a geologist, so I looked him up. Tom Barth (1899-1971) published over 200 papers in his life in the fields of mineralogy, petrology, and geochemistry. When he was young he studied with Goldschmidt and Eskola, names that should be well known to anyone who has ever read a basic metamorphic geology text. He was one of the people involved in the early stages of developing an understanding of the way crystal structure works, and was the first to demonstrate that chemically different atoms can occupy crystallographically identical sites.

What fun serendipity that my host while I was traveling happens to be descended from a scientist whose life-work comprised an important part of the framework that was a necessary prelude to my own research.

Pre-Conference Field Trip, Stop Two: Siccar Point

It has been nearly two weeks since I attended the Pre-Conference Field Trip, yet the memory of the day remains strong. I have already written about Stop One; today’s post continues our adventures as we follow in the footsteps of James Hutton, visiting the unmistakable unconformity at Siccar Point.

This outcrop is said to be one of the most significant in the history of the study of geology. Before Hutton published his theory on geologic time many people accepted Bishop Ussher’s calculations that the earth was only 6,000 years old. However, Hutton’s observations of geologic phenomena led him to realize that it must be far, far older than that to account for the sedimentary record. He observed erosion taking place in the world around him; saw how much sand a river can carry to an ocean over time, and reasoned that this process must have been going on for as long as there have been rivers. The rate at which the sand is deposited onto beaches or into lakes, or along a riverbed is measurable, and so estimates of the time needed to deposit a given thickness of sand may be calculated. He also noted that when sand is deposited by water, it always happens in horizontal layers. Comparing such layers of fresh sand, mud, and/or gravel with layers of sandstone, mudstone, and conglomerate leads one to the realization that the sedimentary rocks must have, at one time, been made up of loose sediment, before they became compacted and/or cemented into solid stone, and any sedimentary rocks which are folded or tilted must have been tilted or folded at some point after deposition and after becoming rock (or the sand would have slid back down into flat layers again).

The rocks in southern Scotland include two very different packages. The older of these packages is made up of Silurian sediments—poorly sorted sandstones (greywackes) which have been folded intensely enough that the bedding now stands on end in many locations rather than horizontally. The younger package is the “Old Red Sandstone”, which was deposited during the Devonian. Hutton knew from his explorations in the region around Edinburgh that the red sandstones are reasonably flat-lying and outcrop to the north of the steeply tilted Silurian greywackes. He knew that there must be some place where the two rock types are in contact with one another, so he and some friends set out in a boat along the coast in search of it.

One can imagine the delight felt by his party when they discovered that contact, at Siccar Point. While it had been possible that there was a gentle transition from the steeply dipping sedimentary rock to the south into the flatter lying sandstones to the north, what they discovered was no gentle transition.

Instead they discovered evidence that the older rocks must have been deposited as typical flat-lying sands and muds of great thickness, transformed into rocks and folded so tightly that the layers now stand on end, the edges of the folds and some unknown amount of rock eroded away, and then, some time thereafter, the sands which were to become the “Old Red Sandstone” deposited atop them, before themselves becoming rock and then being subjected to erosion. Hutton argued that if sedimentary rates in the past operated on the same sort of time scales as they do today there is no way that all of that could possibly happen in so short a time as only 6,000 years. One of his companion on that trip, John Playfair, is recorded as having said that “The mind seemed to grow giddy by looking so far into the abyss of time” when they contemplated just how much time the entire process would have taken.

Indeed, what they couldn’t know as they stood upon this rocky shore contemplating "deep time" was just how much time is represented by just the period of erosion between the two rock units, which has subsequently been calculated at fully 55 million years, during which an ocean basin closed and a mountain range grew.

Unlike Hutton's first boat-trip to this location, our field trip approached the point by bus, traveling south from Edinburgh, and finally stopping in a field near the coast some 55 km to the east of Edinburgh. Travellers are greeted at the stop with a first information sign at the trail head,

and a second when one reaches the point at which one descends to the seaside.

The way was steep, but, fortunately, it wasn’t a rainy day, so the grass was dry, and we made our decent safely.

We then spent a pleasant time examining the rocks, and taking photographs before climbing back up the hill to return to civilization, content in our own observations that yes, indeed, this outcrop does record simply amazing amounts of time.

Pre-conference field trip, stop one: Hollyrood Park, Edinburgh

I’ve been spending a week in Scotland for the MAPT conference. Some people manage to do live blogging of such things. I didn't. (To be fair, they told us in advance that there wouldn’t be a wireless connection available at the conference, so to cut down on the weight I'd be carrying to and from I didn’t bring my computer with me during the days, and have been too busy in the evenings visiting with an old friend with whom I am staying. So I’ll try to post highlights from the conference over the next few posts.

The conference started with a local field trip. We went first to Hollyrood Park, which is in the middle of the city. The most prominent feature of this park is Arthur’s Seat, which is the core of an extinct volcano, which erupted about 350 million years ago. Ten distinct lava flows (olivine +/- other minerals basalt) are distinguished in this area. Apparently there has not yet been a systematic flow-by-flow detailed comparison of the various compositions, if any students out there are interested in the subtle changes that a volcano undergoes during its eruptive cycle.

The second most prominent feature of the park is the sill which makes up Sailsbury crags. James Hutton, (a local man who is known as the father of geology) found an important contact here which helped to settle the debate between the “Neptunists” and the “Plutonists”. The former believed that crystalline rocks formed by precipitating out of sea water, while the latter believed that they had cooled from a molten source.

This outcrop showed that the crystalline rock had intruded into sedimentary layers and in the process, lifted up a layer of sandstone and oozed a short distance underneath that layer. This would not have been possible had it precipitated out of a liquid. Additional proof was provided by his friend, Sir James Hall, the father of experimental geology. Hall owned a foundry, so had access to the appropriate equipment to try melting rock. His experiments proved that one could melt basalt, cool it, and obtain a rock which looked much the same as the starting product. Therefore, the original must also have cooled from a molten source.

Another noteworthy feature of the park is the world’s first example of geological conservation. Hutton observed this hydrothermal vein cutting through the sill, altering the minerals and depositing hematite (iron ore). At the time this area was being actively quarried, and he requested that the quarrymen leave this particular part of the outcrop intact for future generations to observe the phenomena, and they did. The cliff wall is now quite a way behind the preserved portion of the outcrop.

Views from the park include Edinburgh’s castle, which sits upon another volcanic plug.

Stay tuned for my next post, when the field trip moves about 40 miles south to Siccard Point, the site of Hutton’s most famous unconformity.