Wednesday, July 02, 2014

Geology Through Literature - The Travels of Marco Polo


The next story up in the Geology Though Literature thread is The Travels of Marco Polo by Marco Polo. 

Using The Travels of Marco Polo by Marco Polo

While seeming to offer no geological significance, several works can still be used to describe the beauty available in the natural world. The Travels of Marco Polo provides a first person narrative of the travels of Marco Polo across Asia and India during the 12th century. It is this unique perspective that we gain insight into a land and culture that otherwise would be unknown to the outside world of today. Although Marco Polo generally commented on the cultural aspects of the people in which he interacted, he sometimes referred to the geological aspects of the lands and how the people interacted with that geology. It is in these parts that we will focus our attention.

Part 1 - Book 2: Chapter 23

Read Book 2: Chapter 23 (Of the kind of wine made in the province of Cathay - And of the stones used there for burning n the manner of charcoal). A snippet of the chapter is provided below:
"Throughout this province there is found a sort of black stone, which they dig out of the mountains, where it runs in veins. When lighted, it burns like charcoal, and retains the fire much better than wood; insomuch that it may be preserved during the night, and in the morning be found still burning. These stones do not flame, excepting a little when first lighted, but during their ignition give out a considerable heat."
A Breakdown:
    Based on the description of the rocks that Marco Polo had seen, it is clear that he is referring to coal. The province of Cathay is now known as northern China. Looking at the Chinese Coal map below, you can see that there are abundant coal mines across northwestern China, emphasizing the point that Marco Polo was referencing coal in his chapter. There is also evidence that the Chinese have been excavating coal for the past 3500 years. One of the big questions, though is if Marco Polo would have known about coal. In Europe, during Marco Polo's time and before, there were significant coal mines in the 2nd century AD in the UK region conducted by the Romans. However, following the exit of the Romans there were no significant uses of the coal until the 12th century AD, around the time of Marco Polo. And even then, it appears that most of the mined coal remained within the UK region. It wasn't until the 15th century that Britain started to trade coal with the rest of Europe. This makes it plausible that Marco Polo didn't know about the existence of coal.



Some Possible Questions:
1. What rock is being described here?
2. Is the Province of Cathay known for this type of rock?
3. Is it reasonable to assume that Marco Polo wouldn't know about this type of rock in his day ~1250 to 1300 AD?

Part 2 - Book 2: Chapter 27

Read Book 2: Chapter 27 (Of the river named Pulisangan, and of the bridge over it).
"Over this river there is a very handsome bridge of stone, perhaps unequaled by another in the world. It's length is three hundred paces, and its width eight paces; so that ten men can, without inconvenience, ride abreast. It has twenty-four arches, supported by twenty-five piers erected in the water, all of serpentine stone, and built with great skill. On each side, and from one extremity to the other, there is a handsome parapet, formed of marble slabs and pillars arranged in a masterly style... Upon the upper level there is a massive and lofty column, resting upon a tortoise of marble, and having near its base a large figure of a lion, with a lion also on the top. Towards the slope of the bridge there is another handsome column or pillar, with its lion, at the distance of a pace and a half from the former; and all the spaces between one pillar and another, throughout the whole length of the bridge, are filled up with slabs of marble, curiously sculptured, and mortised into the next adjoining pillars, which are, in like manner, a pace and half asunder, and equally surmounted with lions, forming altogether a beautiful spectacle."
A Breakdown:
     The Lugou Qiao Bridge, or the Marco Polo Bridge as it is more commonly known as, still stands today. As described by Marco Polo it contains abundant marble lions statues placed throughout the length of the bridge.  Marco Polo's text states that the pillars are made of "serpentine stone", however I can find no mention of the serpentine stone and he may have mistaken a different variety of marble for serpentine. An interesting note though is that it is often referred that it is impossible to determine how many lions are on the bridge since the statues of the lions contain more lions carved between the feet of the lions.

Some Possible Questions:
1. What types rocks have been included in the bridge construction (i.e. sandstone, basalt, etc.)?
2. Is this bridge still around today?
3. What does that say about the materials used to build the bridge (good, bad, etc.) and was it a good idea to build it in this way?
4. What other name is this bridge also known as?

Part 3 - Book 3: Chapter 19

Read Book 3: Chapter 19 (Of the island of Zeilan). A snippet of the chapter is provided below:
"(The island of Zeilan [Ceylon]) is in circuit two thousand four hundred miles, but in ancient times it was still larger, its circumference then measuring full three thousand six hundred miles, according to what is found in the mariners' map of the world for this ocean. But the northern gales, which blow with prodigious violence, have in a manner corroded the mountains, so that they have in some parts fallen and sunk in the sea, and the island, from that cause, no longer retains its original size."
A Breakdown:
     Today, the island of Ceylon is known as Sri Lanka. Modern day measurements place the island at 833 miles in circumference and 25,330 square miles in area. This is significantly smaller than the measurements given by Marco Polo during his time, as well as the measurements given for the historical size of the island. The earlier measurements and map that Marco Polo was referring to was likely a map created by Ptolemy in 150 AD, almost 1,150 years earlier.
There are questions though as to the ability of Ptolemy to actually measure the size of Sri Lanka though, since his map is mostly based off of estimates by sailors and navigators of the time. Marco Polo as well may have had some difficulty in measuring the size of the island, not possessing the same tools that we have today. However,  I personally question whether the conversion from prehistoric measurements to modern measurements are correct. There could have been confusion translating between Ptolemy and Marco Polo and then Marco Polo and today, giving another form of error.


 Looking at the different size estimates of the island we have:

  Date (approx.) Circum. (mi) Diameter Radius Area (sq mi) Size Difference Rate of erosion
(Sq mi/yr)
Ptolemy 150 3600 1145.91559 572.9577951 1,031,324.03    
Marco Polo 1300 2400 763.9437268 381.9718634 458,366.24 572,957.80 498.22
Modern 2010 833 265.1521352 132.5760676 25,330.00 433,036.24 609.91


If these numbers are correct, then we are looking at rates of erosion of 500 to 600 square miles per year from 150 AD to the present. This is just an astronomical rate and completely unrealistic. The island may be shrinking due to erosion, however there is zero indication that is it shrinking at such an astronomical rate. The possible forces though could change the size of the island are erosion, as stated by Marco Polo, and sea level rise. Erosion alone could not alter the size of the island as dramatically as depicted but sea level rise could, just not over the time period depicted. It is know that historically, humans have been able to walk from India to Sri Lanka across a land bridge produced from drops in sea level. The appearance of this land bridge was last seen about 7,000 years ago though and is far before even Ptolemy's time. The most likely cause for the mysterious shrinking island is inaccuracies in measurements and possibly errors in measurement conversions.

Some Possible Questions:
1. What island is this known as today?
2. What percentage of the island area has eroded away (assuming a circular island with circumference given), according to this description?
3. The earlier map that Marco Polo was referring to is likely a map created by Ptolemy in 150 AD, almost 1,150 years earlier. Calculate out the number of square miles that the island has been shrinking per year (assume 1,140 years has passed).
4. Is this a reasonable rate of erosion?
5. Determine the modern circumference of the island and calculate out the rate of erosion from the last 710 years (Marco Polo's to to approximately modern times. You can use the length of the coastline to calculate a circular area or use the actual area).
6. How do the erosion rates compare?
7. Could Marco Polo's assumption that the island was eroding away be correct or could something else be the cause? Or was Marco Polo incorrect and the island is not shrinking?

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