Archive for April 12th, 2014

Wooster’s X-ray Lab Hosts Expanding Your Horizons

April 12th, 2014

WOOSTER, OH — What a beautiful Saturday for science!!  Expanding Your Horizons (EYH) hit Scovel Hall again this year, and area middle school girls were able to select “Minerals in My Jewelry” as one of the fun science sessions held around campus.  Meagen Pollock, who oversees Wooster’s X-ray Lab, organized and taught “Minerals in My Jewelry”, with assistance from others in the department:  Sarah Bender (’15), Olivia Brown (’15), Elisabeth Gresh (’15), Kaitlin Starr (’16), and Shelley Judge.  The goal of the session was to analyze common jewelry beads using Geology’s XRD in order to determine the correct mineral identification for the beads.  EYH participants then were able to compare the XRD results to actual mineral specimens from the department’s collections.  Then, they made bracelets from the beads that they identified with the XRD.

1-585EYH participants meticulously prepared jewelry bead powders for the Rigaku MiniFlex II X-ray diffractometer, or XRD.

2-585Olivia Brown (’15) oversees one group preparing their sample for the XRD.

3-585Meagen Pollock points to the resultant XRD pattern and mineral identification for a team of students.

4-585Expanding Your Horizon students were able to compare the XRD results to their jewelry beds and to hand-sample mineral specimens.  Here, the group is focused on the purple specimen of amethyst (quartz), which was one of the jewelry beads in the collection.

5-585Sarah Bender (left; ’15) and Kaitlin Starr (right; ’16) are ready to take their group’s sample to the XRD for analysis.  The students, with instruction from Meagen Pollock, actually ran the computer software that controlled and monitored the XRD.

6-585Elisabeth Gresh (right; ’15) works with another group, who is also preparing a sample.  In the background, Provost Carolyn Newton, who visited “Minerals in My Jewelry”, watches the various groups in the room.  After a few minutes of watching the students in action, Provost Newton jumped right in and participated in the activity.

8-585Toward the end of the exercise, Meagen Pollock always made sure that the students could identify all of their jewelry beads in their bracelets.  In the background, you can see that President Grant Cornwell and Peg Cornwell have just popped in for a visit.

Those of us in the department who participated in the Expanding Your Horizons sessions had a very fun day working with the middle school students interested in science, and we look forward to participating again next year!!

Seeing the archaeological site of Shivta through a geologist’s eyes

April 12th, 2014

01 Yoav Shivta 041214MITZPE RAMON, ISRAEL–The tradition we’ve built over the years on our Israel expeditions is to travel to interesting places on Saturdays to take a break from work. Yes, it appears geologists never really stop geologizing, but then that’s not really “work”, is it? Today Yoav, part of his family and I went to the Nabatean-Byzantine city of Shivta to explore the ruins and ponder the role of geology in the development of the settlement. You can find Shivta on the map at N 30.88185°, E 34.62878°. This site was studied by several archaeologists over the years, but I’m most impressed by the visit of T.E. Lawrence here in 1914. (Yes, that Lawrence.)

The questions: Why did this city develop here off the main routes? Did climate change force the abandonment of this city along with many other Negev settlements? Obviously we’re just poking around with these, but Yoav has some really good observations.

02 Shivta drainage 041214Obtaining enough water in this very dry place would have been the first problem to solve. The area has a limestone bedrock that the inhabitants could cut and carve to make many channels to direct storm rainwater into cisterns for storage and use during the dry seasons. Here we see a channel cut directly into the bedrock floor of the city plaza. At the top of the image are rock slabs covering the channel. They would have extended for the whole length to reduce evaporation.

03 Shivta cistern 041214That drainage channel, and many others, leads to this large cistern in the center of the town. It is mostly filled with sediment now. During its use it was many meters deep and had plastered walls to reduce leakage. Archaeologists have calculated that enough water could be stored in this cistern and many others through the city to support the population. This is with present rainfall amounts (about 10 cm a year). These cisterns could be easily built because about a meter below the hard limestone is a soft sandstone that can be excavated quickly.

04 Shivta quarry 041214The building stones for Shivta were obtained in the city itself and a few dozen meters away. Here is one of the ancient quarries. The limestone can be split vertically and horizontal slabs removed for use. You thus only have to cut the stone in two dimensions rather than three.

05 Southern church Shivta 041214This is the beautiful Southern Church. It has a classic Byzantine design. The interiors were made with soft Eocene limestones that could be easily smoothed and carved, while the rougher limestones were used for support out of sight. Some fragments of facing marbles, imported from Italy, can be seen in the alcoves.

06 Stones southern church 041214The stone above is fine-grained Eocene limestone suitable for carving. The stone in the background is coarser limestone. This is a portion of the Southern Church.

07 Shivta rock ceiling 041214Wood is a rare material, so the roofs were made of stone slabs laid across stone arches. Yes, you can imagine the earthquake danger!

08 Northern Church 041214The larger Northern Church is in the background here. Note the thick, sloping walls, especially on the left side.

09 Northern church buttress 041214In this closer view of the walls (and the Avni family dog, Anicha — great outdoor dog!), we see that the bulk of them are made of the rough limestones, and they were constructed to buttress the failing original walls, a smooth portion of which can be seen in the top right. These buttresses were made after earthquakes destabilized the finished walls.

10 Shivta earthquake damage 041214Yoav is pointing here to further earthquake damage to the buttresses themselves. The Shivta people lived through several earthquakes and continued to reinforce their structures.

11 Shivta garden 1 041214To the north of the city is this spectacular garden. It is an experimental plot to see if economic plants like olives, carob and pomegranates can be grown with just the local water trapped in basins in the Byzantine manner. The experiment ended years ago and the plants are doing great.

12 Shivta garden 2 041214This is a carob tree (Ceratonia siliqua), which is an important source of food and medicine throughout the Mediterranean region. Clearly it does well under these circumstances.

13 Shivta garden 3 041214These are olive trees, with a field of wildflowers beneath. With present rainfall amounts enough water can be trapped for agricultural and domestic use in Shivta. The hypothesis that some sort of desertification event (a common idea) ended these desert settlements is difficult to support when the dry conditions of today can still support the original community. It was likely economics and politics that spelled the end of Shivta, not climate change. We also see how critical the local geology was to the early inhabitants of this isolated city. They chose the location well for the agricultural and economic conditions of the time.