The Odyssey and Geology: The Search for Ithaca

This post unifies two of my absolutely favourite topics: geology and classical Greek history. I have always had a soft spot for the classics. In fact, when I started my undergrad I was planning on doing a double major of geology and classics. I decided to focus on geology, but I have not lost my love of ancient civilizations particularly the ancient Greeks and Romans.

Odysseus (Source: Wikipedia)

Most of us are familiar with the story of the Odyssey, but I'll recap it here in a couple of sentences. The Odyssey is the tale of Kind Odysseus's journey back from Troy to his home island of Ithaca. Odysseus, despite being a pretty shrewd guy, angers the god Poseidon who condemns him to wander the ocean for decades before he can go home. During this time Odysseus experiences many wild adventures in is quest to return home to his wife, Penelope and his son, Telemachos. Eventually, Odysseus returns home, but just in time to prevent his kingdom falling into rival hands. Homer obviously took substantial creative licence in the poem, as was customary at the time, however many of the places he mentions are real as are the people such as Agamemnon, Menelaus, Troy, Mycenae, Sparta, etc. However, there has always been a question...where is Ithaca??

This is a question that had baffled classical scholars for decades. At first, many believed that Homer just made up Ithaca since then Troy was believed to be fictional as well. However, once Troy was discovered it no longer made sense to think that Ithaca made up and therefore, it must be someplace amongst the Greek islands.

The passage in the Odyssey that describes the location of Ithaca is as follows:

εἴμ' Ὀδυσεὺς Λαερτιάδης, ὃς πᾶσι δόλοισιν

ἀνθρώποισι μέλω, καί μευ κλέος οὐρανὸν ἵκει. 

ναιετάω δ' Ἰθάκην ἐυδείελον: ἐν δ' ὄρος αὐτῇ

Νήριτον εἰνοσίφυλλον, ἀριπρεπές: ἀμφὶ δὲ νῆσοι

πολλαὶ ναιετάουσι μάλα σχεδὸν ἀλλήλῃσι,

Δουλίχιόν τε Σάμη τε καὶ ὑλήεσσα Ζάκυνθος.

αὐτὴ δὲ χθαμαλὴ πανυπερτάτη εἰν ἁλὶ κεῖται 

πρὸς ζόφον, αἱ δέ τ' ἄνευθε πρὸς ἠῶ τ' ἠέλιόν τε,

I am Odysseus, Laertes’ son, world-famed

For stratagems: my name has reached the heavens. 

Bright Ithaca is my home: it has a mountain,

Leaf-quivering Neriton, far visible.

Around are many islands, close to each other,

Doulichion and Same and wooded Zacynthos.

Ithaca itself lies low, furthest to sea 

Towards dusk; the rest, apart, face dawn and sun.

Od 9.19-26 (text from http://www.odysseus-unbound.org/PDFs/How_did_Homer_describe_Ithaca_ENG.pdf)

So there you have it. The location of Ithaca...it is the westernmost of the Greek islands, which today is Cephalonia, formerly known as Sake, and not Ithaca. As for the current Greek island called Ithaca it in no way meets the description of Homer's Ithaca and therefore it cannot be the same island, unless Homer was trying to play a massive joke on us all or did not understand basic geography, neither of which is very likely. So where did ancient Ithaca go?? 

Over the past few years a new theory has emerged to answer this question. In short the idea is that the thin isthmus of land between Paliki and the rest of Cephalonia was at one point underwater separating the two places and resulting in two islands. Indeed, there is classical text to back up such and idea. Strabo, the renowned ancient geographer wrote "where the island is narrowest it forms an isthmus so low-lying that it is often submerged from sea to sea." If we trust Strabo, this means that during classical times there were actually two islands that are now one. Perhaps, westernmost Paliki was Ithaca during Homer's time and the current island called Ithaca was another island was Doulichion. However, how can we prove that this idea is more than just an interesting theory?

Elevation map of Cephalonia. The white test is the current names and the yellow text is the name in Homer's time. (Source: Odysseus Unbound)

Well, to answer this question we must turn to geology....we had to get there sometime.

The geological investigation of Stabo's channel, now known as the Thinia valley, is being carried out by John Underhill, a professor of seismic and sequence stratigraphy in the University of Edinburgh department of geosciences. The geological evidence that Strabo's channel existed is outlined in a paper by Dr. Underhill published in Nature Geoscience and is freely available online. However, I'll give a brief outline of the evidence here.

In order to prove that Paliki was once an island the geology must show that the Thinia valley was once under water. However, the problem is that the elevation of the Thinia valley is 180m above sea level...and sea level certainly has not changed 180m is only 3000 years!!! However, there are other geologic features that can account for some of the uplift. The Eastern side of the Thinia valley is divided by a large thrust fault known as the Aenos Thrust, which is an extremely active fault to this day. Indeed, the last major earthquake on Cephalonia was a 7.2 magnitude in August 1953. The seismicity is generated by the collision of the Eurasian plate with the African plate. However, the earthquakes, while they cause substantial uplift did not occur often enough or have enough displacement to result in over 180m of uplift since the time of Homer. Therefore, another mechanism is needed to fill in the valley and raise it to 180m. Mapping of the island and the valley revealed a possible solution to this problem. The mapping revealed the occurrence of several large landslides and rockfalls in the valley. In fact, large blocks from the valley walls are easily observable within the valley. These massive landslides and rockfalls were caused by the earthquakes and storms and a lot of material fell from the steep valley walls into the valley.

A resitivity survey of the Thinia valley. The blue is Cretaceous bedrock, red is water, and the green and yellow are unconsolidated sediments. (Source: Odysseus Unbound)

To further prove the existence of Strabo's channel, however, direct evidence of marine sediments must be observed underneath all of the landslide fill. In order to do this Underhill's team drilled numerous boreholes around the valley and found numerous places where there was indeed marine sediment. In addition to drilling they also conducted geophysical surveys in order to map the subsurface geology of the valley in greater detail, which would allow them to map the channel and prove that it actually separated Paliki from the rest of Cephalonia. The geophysical techniques allowed them to determine the amount of fill in the valley from landslides, the depth to bedrock and the bedrock contours. Further surveys also revealed that there were drainage features in the sediment of the embayments on either side of the valley which shows that water flowed into the sea through the valley. Combing the boreholes, and the geophysical mapping the evidence points to the fact that Strabo's channel did exist 2000-3000 years ago and that since that time uplift from earthquakes, landslides and rockfalls filled in the channel and joined Paliki (Ithaca) to the rest of the Cephalonia concealing Ithaca us!!!

Thanks for reading and please feel free to post any questions or comments!

References:

Odysseus Unbound: http://www.odysseus-unbound.org/

Underhill, J. (2009). Relocating Odysseus' homeland Nature Geoscience, 2 (7), 455-458 DOI: 10.1038/ngeo562

Trip to Mer Bleue

Recently I went hiking in Mer Bleue. Mer Bleue, for those not from the Ottawa area it is a large peat bog just outside of the city, that has several really great hiking trails and board walks through it. It is also an interesting place geologically and is internationally recognized as a wetland of importance.

Mer Bleue (Google Maps)

The most striking feature about Mer Bleue is the large peat bog, dominated by sphagnum moss and other bog plants like labrador tea. Ottawa is not actually an area one would associate with a peat bog such as this. Indeed, the ecosystem is a boreal habitat which is much more fitting in the Arctic as opposed to southern Ontario. The reason that Mer Bleue exists lies in the history of its formation.

Mer Bleue formed around 9,500 years ago at the end of the large continental galaciation that covered almost all of Canada. As the ice sheets melted a large glacial lake called Lake Champlain was formed in southern Ontario and deposited lots of lacustrine and marine clays in the area. However, once the weight of the glacier was removed from the area the land began to rebound upward. This is known as isostatic uplift. This uplift caused much of the lake to drain into the Atlantic Ocean. As the glacier continued to melt the river of water that resulted incised three deep channels into the clay, which is why it looks like Mer Bleue has three fingers. The raised areas between the fingers are actually sand dunes that were above water at time. As uplift continued the area was cut off from the early Ottawa River and became a small lake. Over the time this lake filled with bullrushes and other boreal plant species like sphagnum, which eventually took over the lake. This led to a build-up of organic matter within the lake and caused the oxygen levels to drop turning it into a bog.

Today the bog remains and is surrounded by a fantastic hardwood forest. It continues to be a popular tourist attraction and is a great place for a picnic. The bog is also the subject of research and several scientific papers have been published outlining its history, the carbon balance and hydrogeology of the bog. My visit was purely for pleasure, although I have been considering doing some research there too.

There are cool mushrooms in the hardwood forest on the dunes. Not sure what type this is. 

More cool mushrooms. Again, no idea what kind though.

The very sudden transition from boreal forest to sphagnum bog. 

Overlooking the sphagnum bog from the boardwalk

A green frog.

Thanks for reading and please feel free to comment.

Matt

Exciting Elements #1 - Iodine

This is the first installment of a new series title Exciting Elements. Exciting Elements will be a profile of an element on the Periodic Table. However, since this is not a chemistry blog, but a geology blog, the posts will concern the geochemical behaviour of the subject element. For example, each post will contain info about how it moves in the environment, are there environment toxicology risks associated with the element, does it form minerals, how do we detect it and can it be used to answer questions about the Earth.

Interested yet??? Well, you should be since there are 118 elements in the Periodic Table (although not all relate to geology very well) and I aim to blog about them. So hold on to your pipettes!

I have decided to proceed in no particular order, at least at the start, so we will be jumping around all over the table and the first spot that we will land is on element number 53 - iodine.

I figured that iodine would be a good place to start since I am doing my Ph. D. on the the geochemical behaviour of this element and it is always good to start off with what you know....of course this means that iodine has officially taken over every aspect of my life.

Discovery


Iodine was initially discovered by French chemist Bernard Courtois in 1811. Courtois was a gunpowder manufacturer during the Napoleonic Wars and was making sodium carbonate, required for the production of saltpetre by adding sulphuric acid to seaweed. One day he added too much acid and a purple vapour rose from his sample and then crystallized on cold surfaces. This was the first synthesis of iodine.

The name iodine originates from the purple vapour that emanates from native iodine and is derived from the Greek ἰοειδής which means purple.

Pure iodine. Even though it looks like a metal, it is not. It is actually a halogen. (http://images-of-elements.com/iodine.php)

Isotopes


The most common isotope of iodine is iodine-127, which is stable and makes up 100% of the natural inventory of iodine. However, there are also a few radioactive isotopes of iodine that are of interest either as tracers of natural processes or because they pose health risks.

The most dangerous of the iodine isotopes in terms of the health risks it poses is iodine-131. 131I has a half life of 8 days and has received substantial media attention since it was one of the major isotopes released by the Fukushima disaster. It is even more dangerous because iodine is readily absorbed into plant and animal tissue. In humans iodine is absorbed into our thyroid gland and this means that if 131I is present it can be absorbed by our bodies and hence is more dangerous due to internal exposure.

Iodine-129 has half life of15.7 million years, is the subject of my PhD. thesis, and is not nearly as dangerous from a health perspective as 131I, however it is still of interest (otherwise I'd be in big trouble!). 129I is produced naturally in the atmosphere by cosmic ray interaction with xenon gas, in rocks by the spontaneous fission of uranium-238 and by humans, in nuclear fuel reprocessing plants or nuclear disasters and atomic bomb testing. In fact, before humans the amount of 129I on Earth was about 250kg, now it is about 6000kg.

Iodine-125, which has a half-life of 59 days is a minor radioactive isotope of iodine, although it is used in many laboratories as a tracer of lab methods and can also be used in medicine. There are many other isotopes of iodine that are extremely rare. Some of these can be useful in medical imaging, but most simply are produced naturally and decay rapidly without anyone really noticing/caring.


Behaviour


Iodine is a member of the halogen group found on the right side of the Periodic Table. In nature it behaves similarly to chlorine. The most important thing to know about iodine in nature is that it is always in motion. What I mean by this somewhat cryptic sentence is that it can be found in the hydrosphere, atmosphere or biosphere and transfers between them with ease; either as part of a volatile or soluble organic compound or inorganic compound depending on the local environmental conditions, such as pH, oxygen rich or oxygen poor conditions, and organic content. My thesis is on the movement and sources of iodine in the Canadian Arctic so trying to understand this more fully is part of what I hope to accomplish with my research.

Dr. Udo Fehn (http://www.earth.rochester.edu/fehnlab/index.htm) This figure shows where iodine-129 is produced and where it can be found in the environment. It does not include anthropogenic production. The t is the residence time of iodine in each place. e.g. 18 days for the atmosphere. 

One of the reasons it is really important to understand the behaviour of iodine well is in the field of nuclear waste storage. When we store nuclear waste it is essential that the waste be isolated from the environment for long enough that all the dangerous isotopes decay. However, when we store reactor fuel there is lots of iodine-129 present that has a long, long half life. This means that any repository for nuclear waste has to actually be designed to keep 129I secure, even after everything else has decayed away. However, should the worst occur and the waste leak or another Fukushima occur it is pretty important that we have a good idea of how iodine behaves in the environment!!


Minerals 
Iodine minerals are few and far between. The most common are: elemental iodine (I2), iodoargyrite (AgI), and marshite (CuI). There are several others, but they are generally quite rare. For a full list see: http://www.mindat.org/chemsearch.php?inc=I%2C&exc=&sub=Search+for+Minerals

 Iodoargyrite. (http://www.mindat.org) Locality: Schone Aussicht Mine, Germany (4mm)

Some iodoargyrite that I synthesized in my lab for accelerator mass spectrometry analysis of 129I in river water from the Yukon Territory, Canada (Photo: M. Herod)

Most of the iodine mined today is found in Chile, but some is also mined in Japan. The deposits in Chile occur as caliche. Caliche is a bit of a mystery to me, so the information that I am distilling here comes from Sirocco Mining Inc. which is a major producer of iodine. Caliche is a sedimentary rock usually composed of calcium carbonate that forms in arid soils. It forms when minerals in the upper layer of a soil are dissolved by rain and then re-precipitate below in a deeper soil horizon. This usually takes place in arid to semi-arid environments. The caliche of Chile is unusual in that it contains high concentrations of unusual elements such as iodine. Most caliches are composed of calcium carbonate, but oddly the Chilean caliche is mainly composed of nitrates. The reason for this is not clearly understood, but the overall formation is still similar. It is believed that the nitrates, iodine and other salts were dissolved in highly saline ephemeral lakes in the desert that would evaporate depositing their salts, which would then slowly get leached and form caliche deposits.

Uses


Over the years iodine has been used in many different applications. Perhaps the most well known is as a disinfectant. It was not that long ago that if you cut yourself in order to disinfect the would all you had to do was slap a little iodine on it. Indeed, it is still possible to buy iodine as drops that can be used to purify water in the field (although I am not fond of the taste).

Radioactive isotopes of iodine are used commonly in medical imaging as well as in some cases as radiation therapy for cancer. In fact, 131I can cause thyroid cancer but can also be used to treat it.

Many countries use iodized table salt to help make sure that the population has enough iodine in its diet since iodine is a very essential micronutrient and iodine deficiency is actually a very real health concern in many places.

Let me know what you think about iodine or if you have any questions. Also, what should my next element be? First suggestion wins!

Matt

References: 


MinDat: http://www.mindat.org/

Sirroco Mining Inc. Aguas Blancas Project: http://www.siroccomining.com/s/AguasBlancas.asp?ReportID=109021


Argonne National Lab: http://www.evs.anl.gov/pub/doc/iodine.pdf