Wednesday, March 19, 2014

How tall was this pyramid (answers)

Due to overwhelming demand, I am giving my answer to the question of how tall our pyramid would have been when first built. The angle of the facing stones is about 73 degrees, and if you just do a calculation on that basis (yes, it’s trigonometry), you get a height of about 43 meters.

If you do a more detailed (and accurate) calculation based on the size of the blocks and the setback of each course, you find that the pyramid had about 72 courses of stone and that it was about 34.5 meters high.

These calculations are remarkable partly because the pyramid has a much lower angle now, and it’s only a bit over 9 meters high. So a very rough reconstruction shows what the profile of the pyramid would have looked like originally:

Is that even remotely plausible? Where did all that stone go??

We looked at some nearby sites, and it seems that it is plausible—there are some pyramids at the site of Nuri from about the same period of time that were built of solid stone and have survived better, and they could have been close to 34 meters high. They also have a profile like the one I’ve reconstructed here.

Pyramids at the site of Nuri

We don’t know where all the stone went…but some of it seems to have been used in the village over the past century or two. 

Conservation in action!

My friend and colleague from the Kelsey Museum at the University of Michigan, Suzanne Davis, has arrived to conserve and restore our finds, to consult on issues of architectural preservation (our local sandstone is mostly of really poor quality, very soft), and to help us think through our longer-term site management plan.

I haven’t talked much about objects we’ve found this year. It’s been an unusual season since so much of our effort has gone into excavating monumental structures that have mostly been cleaned out. The city wall soundings produced some whole ceramic vessels that had been left in medieval houses—you can see a couple of them being repaired on Suzanne’s table. They have bandages wrapped around them as if they had head wounds… We also have some Meroitic painted pottery from an upper level in the temple that should look nice when it’s put back together. And of course Suzanne does all this much better than we archaeologists would do on our own, so it’s great to have an expert here.

Tuesday, March 18, 2014

How tall was this pyramid?

Here's a real-life math problem: How tall was our pyramid when it was built? You can see that it has some original stones left toward the bottom, but the upper part is all rubble that would originally have been invisible behind a nice stone facing.

We are working on this question ourselves. Here is what you need to know...first, the base is 26.65 meters on each side. The pyramid has one course of stones with a vertical face (called the "plinth course"), then a series of stones with a steep angle--much steeper than the current slope of the pyramid. Here's a drawing that shows the slope of the stones.

Each course of stones is 48 cm high. The angle of the stones is such that if you draw it on graph paper, the top of the course is 11.5 cm back from where a vertical face would have been. (I never knew how hard it could be to write math problems...). This is shown by the triangle with dotted lines above.

In addition, the face of the pyramid was not smooth...each course was stepped back by about 7 cm on average. 

So, you should be able to calculate the original height of the pyramid using all that information. We're working on it too...but let's let the 6th graders (and younger) try this before posting any answers.

Saturday, March 15, 2014

More work of the Sudanese team at El Kurru

The Sudanese team working at El Kurru is directed by Prof. Abbas Sidahmed Mohamed-Ali, with Prof. Jamaal Karfis of the University of Dongola at Karima (pictured here) as field director. We have had a chance to become good friends during this field season. The Karima team is continuing to clean and restore the dramatic tombs of the kings and queens of Kush who also ruled Egypt as its 25th Dynasty.

In this photo, Prof. Jamaal is standing in the tomb of Queen Khensa. At El Kurru, a group of the major 25th Dynasty queens was buried in a cluster to the south of the royal cemetery (another group of probably less-major queens was buried in a cluster to the north).

Khensa was a daughter of king Kashta (whose name means “the Kushite”). Kashta was also father of king Piye (Piankhy), who was the first king of Kush to campaign far into Egypt. And Khensa was the wife of Piye, her brother (or half-brother), which was a common practice in the royal family of Kush.

I have my own connection to Queen Khensa. In an earlier excavation in the 4th Cataract region of Sudan, about 50 km upstream from El Kurru, we found a clay seal for an ancient jar that was impressed with the royal seal of Khensa. We found it on a gold-mining site that we were excavating, and it seems to suggest that the queen herself was involved in supervising extraction of gold from that region.

Friday, March 14, 2014

National Geographic film crew is here!

We’ll be part of a National Geographic film being made about the empire of Kush, and the film crew is here! The producer/director, James Barrat, has been interesting to talk to because he asks creative questions that we haven’t always considered before…and the NGS team has been great to work with. Here, I am getting ready to try using a robot with a camera to look into one of the inner rooms of the temple. I’m getting help from my Sudanese friend and colleague, Mansour Mohammed Ahmed, who is our foreman (he supervises all the local workmen).

Thursday, March 13, 2014

Kings and Queens of Kush

Here’s one more note for the 6th graders in Ms. Donnelly’s class. They asked about what we hope to find in the burial chamber in the pyramid, and whether the kings and queens of Kush were mummified like Egyptians. They also wanted to know if there might be traps waiting for us in the burial chamber.These are pretty complicated questions. First, about traps…we don’t know of any Egyptian or Kushite burials that had traps for robbers, even though the ancient builders knew that robbery was a problem even in ancient times. Instead, they tried different ways to hide the burial, by covering it with sand or rocks, or by building false doors and tunnels. So, we don’t expect to find traps!

We are worried about how stable the underground burial chambers are now, though. I wrote earlier about how George Reisner decided not to excavate this pyramid in 1919 because he thought it was unsafe (and he had a lot of experience at that point with excavating pyramid burials!). Reisner did excavate the outer room, but the second room suffered a big roof collapse. Here’s a photo (above) of the hole in the ceiling of that room. You can get a better idea of the size of this hole from the second photo (right) that shows me and Nacho standing up inside. It’s big enough to represent a big weight of stone that fell down at some point in the past. We’re just to the point of installing a protective structure inside the tomb that will allow us to excavate down to the floor in the next week, at least in part of the room.

Kushite kings and queens adopted many aspects of Egyptian burial practice, including pyramid burial and some parts of mummification (although the burials were so thoroughly looted that it’s difficult to be very precise about it). But they never gave up the idea that they were being laid to rest—even the kings and queens were buried on beds, and we find the holes in the stone for the bed legs whenever we excavate the burial chambers of these pyramids. 

Tuesday, March 11, 2014

Temple update: new capitals

We have continued to work on the mortuary temple that we think was devoted to the cult of a dead king (or maybe all the dead kings and queens in the cemetery). It’s a large building, and we have now nearly excavated the entire outer room with 26 columns. Stay tuned for a photo within the next week.

The temple has a series of underground chambers cut into the rock. You enter this network of rooms through doorways into two rooms that were decorated with stone columns. Each of those rooms has three further doorways (one pair of doorways seems to lead to a passage that connects the two rooms), so we have a network of at least 6 rooms and a passageway. The outer rooms are carved on a nice scale—it’s easy for us to stand up in them, with plenty of head room (I don’t think I could reach the ceiling).

The eastern room is especially fancy—its columns have two different types of capitals. The photo above shows one pair of capitals, which are in the form of palm tree branches. You can also see in that photo what looks like a bite taken out of the lower part of the column. There was a significant erosion event in the rooms at some point later in their history in which the columns and walls were heavily worn at a single level.

You can just see the front pair behind our architect Nacho in this photo—they have five spirals. The column that Nacho is working on was worn so heavily that it broke and slumped down, and one of the stone beams on top cracked. Nacho is working to remove the beams so that they will not contribute to further collapse of the column.

The outermost rooms were essentially empty of objects. We are still hoping for more clues as to the function of this complex of underground rooms…

Thursday, March 6, 2014

Medieval Christian settlement at El Kurru

One of the surprises of our work here at El Kurru has been the discovery of an apparently extensive Christian settlement of about 900 AD. The city wall we have been tracing seems to be of this date rather than the Napatan date of perhaps 700 BC that we had expected.

We have now traced the city wall itself over a length of about 35 meters. We have taken a series of kite photographs that are joined together by photogrammetry software called Photoscan into a 3D model that can be rotated and viewed from any angle. Photos and model by Kathryn Howley of Brown University and Martin Uildriks of the University of Leiden. Here is an early example of a view taken from the digital model of the city wall.
The excavator who has been responsible for most of the work along the city wall, Martin Uildriks has also located and excavated a gate in the wall. The photo shows several door sockets that show that the gate was built and rebuilt. It also shows a massive piece of petrified wood that was used as a threshold during one of those phases. There is a petrified forest out in the desert to the northwest of El Kurru, and although we regularly find large and small pieces of petrified wood in our excavations, this is the first time we’ve seen it used in architecture.

Another excavator working in this area is Dr. Tim Skuldboel of the University of Copenhagen. One of his soundings against the city wall gives us a glimpse of the Christian settlement—part of a small house, with a hearth in one room. In a later phase, the house collapsed and was used as a location to dump trash, and finally, burials were dug into the deposits. 

Tuesday, March 4, 2014

Life on the dig

Another installment of answers to Ms. Donnelly’s 6th grade class that have to do with life on the dig….

We live in a house in the village—here’s a photo of the outer courtyard, which is really a nice place to have a cup of tea in the afternoon, and we do a lot of work here too as you can see.

It gets light here around 7 am. We get ready, have our tea and coffee, and start work at 8 am. We have hired around 70 local men to help with the excavation, and most of them prefer to work from 8 to 2 even though it gets hot here in the afternoon (it’s recently been between 95 and 100 degrees Fahrenheit in the afternoons).

We eat according to a Sudanese schedule: “breakfast” is a big meal at 11 am, and we have “lunch” a bit late for Sudan, at about 6 pm. They would normally have dinner at 9:30 or so, but we are all too tired, so we have just two main meals. We eat a local, organic, and mostly vegetarian diet—lots of fava beans (called “fuul”), eggs, tomatoes and cucumbers, sometimes pancakes with savory sauces, and bread with everything. And we eat Sudanese style, with our right hand, mostly using little pieces of bread to scoop up the food. My personal favorite is the sweet spaghetti they serve with every meal—hard to eat with your hand!

We work six days per week, with Fridays off. We are a pretty active group, though, so we sometimes catch up on work on Fridays, and sometimes drive off to visit other sites in the area, which is important for us.

I’ll write more later about the physical process of digging!

Geology and El Kurru

I’ve encouraged the team to write guest-blog posts too. Here’s a note from our geologist/geophysicist, Dr. Carola Stearns, along with a photo of the area she’s working in—the mortuary temple:

The landscape around El Kurru is one of remarkable contrasts: dry vs. wet. We are here in the dry season. The temperatures are slowly rising and the air is very dry. There is absolutely no hint of rain in the atmosphere nor water in the dry wadis (creek beds). Yet in the excavation of the outer room of the temple we uncovered spectacular evidence that a single flood of the adjacent wadi was powerful enough to breach a large section of the outer wall of large, cut sandstone blocks. This must have happened shortly after the original inhabitants abandoned the site. Over time the outer rooms of the temple were filled with almost 2 meters of wadi sediments. Flooding last year deposited sediments all the way into the interior rooms of the temple.

We are situated on the southern edge Nubian plateau where all that remains of formerly extensive outcrops of Cretaceous-aged fluvial  (riverine) sandstones, conglomerates and siltstones are occasional small jebels (mesas). These are small erosional remnants in a landscape in which water has played a strong role in the past. Although erosion is continuing today, the pace of the denudation has slowed considerably. Most of the scenery is an unvegetated, slightly undulating bedrock surface with a thin veneer of gravel and, in places, windblown sand. Just north of the village, a petrified forest crops out. Large (> 2 foot) diameter trees felled and then were buried in sediments and then turned to stone by percolating silica-rich waters. Today, the only vegetation is the palm trees and crops in the irrigated lands adjacent to the Nile. It is a sharp contrast to imagine the lush, forested floodplains of the Cretaceous rivers in the same location of the barren desert landscapes of today.

Saturday, March 1, 2014

Pyramid update

It’s been a very busy week on the dig, and I haven’t had so much time to write. But I can give an update on the pyramid now.

We had completed excavating the stairs a bit over a week ago, and opened up the door block that we had put in over the hole that looters cut into the stone.

I should say something about looting here since I’ve had questions about it…all the royal tombs of Nubia that have been excavated so far have been looted, often soon after the burial. Looters were after gold objects mostly, and they often leave behind many things that are of interest to archaeologists. So excavating a burial that we expect has been disturbed is still worthwhile.

The looter’s tunnel seemed to lead into an outer chamber that George Reisner had excavated, and from there, we could move into the inner chamber that may have been the actual burial chamber if there are not doorways leading further under the pyramid (Reisner seems to have thought that there are 3 chambers in all).

We had at least 3 problems…the first is the seemingly simple act of removing all the sand that had accumulated in the outer chamber since Reisner’s time. Fortunately, we have on our team an architect who has worked on tombs in Egypt, Ignacio Forcadell (everyone calls him Nacho—he’s in the red helmet in this photo), and he immediately began designing a platform to support a system of ropes, pulleys, and buckets that has more than tripled the speed at which we can move sand out of the chamber.

Our second problem was the fact that the ceiling of the inner chamber has collapsed, and that there is danger of further rockfall—this is why Reisner didn’t excavate the second chamber. Nacho is working on a plan to protect against further collapse.

Our third problem is the overpowering smell of bat guano. Really unbelievable—when we first got into the chamber, even holding our breath was not enough, and our eyes watered.

More on these problems soon!

Life in the village

I received a nice note from Julie Donnelly, who teaches at Clague Middle School in Ann Arbor, Michigan. Her 6th grade students had a bunch of really good questions about the dig and about living in a village in Sudan. It turns out that 6th graders are pretty smart! I’m going to try to answer their questions in several posts over the next week or two.

One group of questions was about life in the village.

There are maybe 1000 people living in El Kurru village (nobody seems to know for sure). The village is modern in some ways. There are four shops on the main street, including Waleed’s grocery store (above), the barber shop where I got my haircut, and a coffee shop that would amaze you—a woman making the delicious local coffee called jebena on coals that rest on the floor, which is sand. So, not a lot of businesses, but there are a few. People drop by the grocery store all day long…women sometimes feel more comfortable shopping through a window on the side of the store rather than going inside.

Nearly everyone here has a cell phone…one feature they enjoy is an ability to play the radio out loud on their phone while we are all working in the excavation. In fact, Sudanese went from having a pretty minimal wired phone network to a complete mobile phone network in a very short period of time in the last 10 years or so, and it is changing everything about working and living in Sudan.

And yes, there are mosques in the village and we hear calls to prayer throughout the day (with loud calls to prayer starting at 5:45 am!). The person who gives the call to prayer is called a muezzin, and we all have our favorite ones. This is one of the more observant Muslim places I’ve worked, and many people in the village go to the mosque to pray 5 times a day.