Chalk Talk

Wanna work long hours?  Get dirty, burn yourself on candles, lightbulbs?  Work in the pouring rain and the heat of Israel summer?  Have access to “natural” rest rooms? Climb up and down and up and down the side of a hill, often carrying heavy loads?   Do you like shlepping rocks?  Instructing people in the correct use of a pick axe?  Having 2200 year old dirt perpetually stuck beneath your fingernails?  Chalk dust always in your hair?   (Hillel claims that my hair is gray, but I am sticking with the chalk dust story.) Climbing through small openings as much as 3 floors underground?

Do you genuinely want to work with people discovering the past?  Does it excite you to know that you may find a piece of pottery with Hebrew letters written 2200 years ago?  How about a part of a glass bracelet from Sidon or a toga clip?  Maybe you get turned on by ancient coins?  Do you want to know how people lived and worked in the time of Alexander the Great?  Or maybe find connections between ancient texts and archeological finds?

All of these activities are part of my work at Archeological Seminars Dig-for-a-Day program in Maresha/Beit Guvrin.  I started working there 16 months ago, and I truly love it.  I love working outdoors, working with my body, working with people, and the continual magic of discovery when you are doing archeology with people who come with a fresh outlook.  But one other element draws me to the work:

I LOVE CHALK !

When I was in Tour Guide school, geology was not the most beloved topic.  Most people who become Tour Guides in Israel have as their first love history or some related discipline.  While these things are definitely important and the majority of visitors to Israel want to explore some part of the history of Western culture, I also have a  scientific bent.  This quickly became known in the class, and I wrote up many explanations of the more scientific topics which arose, including a few on geology.

To most people, maybe, a rock is a rock is a rock.  They have different colors and properties, but other than identifying them have no bearing on life.  Chalk does have that pristine whiteness, smooth contours, lovely uniformity.  That stuff is all nice, but for me, living in a place with varied geology, I like to see the connections between the rocks and the people.  Different rocks lead to different soils, which in turn are better for growing one type of crop, for example.  Maresha/Beit Guvrin is built on chalk.  This affected the type of life they were able to lead.  Because the chalk is so easy to work with and quarry, the people living in Maresha were able to do much of their work in these vast systems of  underground “basements”.  To date, 5000 different cave rooms have been found in Maresha, many with columbaria, olive presses, cisterns, or cultic shrines.

So, a bit on chalk.

Dolomite, Limestone, and Chalk are all basically the same chemically.  CaCO3 (Calcium Carbonate).  They are all marine sedementary rock forms made from sea creatures.

Dolomite is formed at a sea depth of 2 – 5 m.  (under a mite of pressure)
Limestone is formed at a sea depth of 20 – 50 m.
Chalk is formed at a sea depth of 200 + m.  (under lots of pressure)

The three form differently because of the different sea creatures which live at different depths.  (Are we all thinking “Goldilocks and the Three Bears?  In shallow waters, we have big papa sea creatures; in medium waters, we have medium mama sea creatures; in deep waters, we have wee baby sea creatures.)

Chalk has the possibility of having a layer of Nari on top of it.  “Nari” comes from the Arabic “Nur” which means fire.  This is because the Nari looks like burnt, cooked Chalk.

Chalk also features predominantly in the Judean desert and in the area of Tzfat, but there is no Nari there.

When does Chalk form Nari and when not?

According to the research by Yaacov Goldberg,  Chalk forms Nari in only very specific conditions of the proportion of annual rainfall to annual average temperature.  When this ratio is between 15-30, Nari can form.
Examples:
Shefela:  Average rainfall:  400 mm, Average temperature: 20, 400/20 = 20  – formation of Nari
Judean Desert:  Average rainfall:  100 mm, Average temperature:  20, 100/20 = 5 – no Nari
Tzfat:  Average rainfall:  600 mm, Average temperature:  15, 600/15 = 40 – no Nari
Beit  Shearim:  Average rainfall:  650 mm, Average temperature 26, 650/26 = 25 – Nari

But let’s get back to Chalk and People….Chalk is really important in the history of Eretz Israel.
The Bar Cochva revolt could not have happened without chalk.  This stone which is so easy to quarry made for quick construction of escape tunnels and hiding places.  Interestingly enough, in the North near Usha where they now think there may have been Bar Cochva activity, the surface rock is Chalk.

Chalk from the bell caves in Beit Guvrin (next to Maresha and later)  built the Arab cities of Ramle and Ashkelon.

Wine presses cannot be made directly in Chalk.  Despite the number and variance of industry in Maresha/Beit Guvrin caves, you will not find a single wine press inside a cave.  The chalk chemically reacts with the grapes and sours the wine (don’t try this at home – I did, and it was not fun).  We do find wine presses in caves in the Jerusalem hills, but again this is not chalk but Limestone, so all is good.  Wine presses in the Shefala abound, but only in the Nari on the surface.  (I have not yet tried making wine on Nari, but this science experiment is the next to come.)

I could go on and on about chalk, or other geology which influence the truly rich history and culture of Israel.  This is just a dusting with hopefully more to come.  Enjoy life!

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2 thoughts on “Chalk Talk

  1. Pingback: The Light of Fire | Leiah Jaffe

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