Wednesday, April 26, 2023

Links: Crust Evolution, CO2 Emissions, DNA Structure

I'm posting a reading list after a long interval. Hope you like this selection. 

1) Secular Evolution of Continents and Earth Systems. The earth's outer shell has evolved and changed in its chemical and mechanical properties over time. This long term evolution has had profound consequences for geological and biological processes. Peter A. Cawood and colleagues have written an informative article in Reviews in Geophysics on the geologic history of the continental crust and its value as an archive for earth processes. The paper is open access, and there is also a shorter Q &A with lead author Peter Cawood which I have linked to in the title. 

2) Carbon dioxide removal is not a current climate solution. What is the best approach to limiting global warming? Do geoengineering methods which remove CO2 from the atmosphere offer a way out? David T. Ho, using a simple and effective explanation, refutes that notion and argues convincingly that drastic emission cuts is the only way to slow down temperature rise.  

3) Rosalind Franklin's contribution to the discovery of DNA's structure. 1953 was a standout  year in our understanding of life with the publication of papers proposing a structure for DNA. Rosalind Franklin's role in this story has been either sidelined or misunderstood until recently. The authors of the linked essay, Matthew Cobb and Nathaniel Comfort, are writing biographies of Francis Crick and James Watson respectively. They recently went through Rosalind Franklin's notes and some other unpublished documents which helped them piece together a different account of the discovery of the structure of DNA and Rosalind Franklin's key insights. 

This essay goes beyond the popular eureka moment narrative which held sway over people's imagination for a long time. Instead, we find collaboration between the teams working on this problem and many twists and turns before Watson and Crick came up with the solution. The article also raises important issues of ethics and sexism in science. 

Thursday, April 13, 2023

Exploring The Panchachuli Glacier Geotrail This May

Folks, join me for a walk to explore the geological landscapes near Panchachuli Glacier, Darma Valley, Kumaon Himalaya. The plan is from May 7 to May 13 2023.

This geo excursion is being organized by Deep Dive India. I will be the geology expert accompanying the group. We will be observing a variety of geologic terrains made up of rocks that tell a story of Himalaya mountain building. High grade gneisses and migmatites, leucogranite dikes and sills, mica and garnet schists, sandstone and conglomerates. As we walk along the terrain we will observe how rock varieties change and what that tells us about the very process of continental collision and Himalaya orogeny. 

There are glaciers too! The Panchachuli Glacier dominates this region. The landscape is littered with moraines and glacial lake and stream deposits. Their locations along the valley hint at fluctuating climate and glacial growth and retreat. 

The terrain will be categorized by trekking companies as '√©asy to moderate'. We will be walking about 4 to 5 hours daily. It is really a very accessible region and you can get close to some fabulous geology. 

Do contact Deep Dive India if you are keen on joining us. The contact details are in the graphic.     

You can email me too at Email subscribers, as you know, I have switched to a new delivery service. tech support is still working to fix a glitch with the The Reply-To button. In case you need to email me, kindly put in my address manually.

Friday, April 7, 2023

Pavement Geology: Pegmatites

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Pavement Geology:

At a new construction site, just a few minutes walk from my house, I came across these polished countertops used on building exteriors.

Isn't it a beauty? It has the texture of a pegmatite. These are a variety of igneous rocks made up of large interlocking crystals of feldspar, quartz, mica and smaller amounts of minerals like tourmaline, hornblende, calcite and many others. They crystallize from a magma rich in dissolved water and other volatile elements like flourine and chlorine. The presence of these fluids enhance the delivery of elements to sites of mineral growth, enabling the crystals to grow to a large size. 

This counter top has amazingly large faceted white feldspar crystals set in an oily grey quartz rich matrix. 

I wondered where it was from? And as I stood there, I wondered whether it was a natural rock or an engineered composite. I could not get close to feel the texture and hardness, but there is a sure shot way to distinguish natural from artificial rock. Always look for identical repeating patterns.

On another panel, I found the exact same crystal association.

The crystals had the same cleavage, cracks, inclusions, and resorbed edges (uneven jagged boundary due to reaction of the crystal with the remaining magmatic fluids). Natural products will be variable. This is definitely a synthetic material perhaps with a printed laminate mimicking a geologic texture.

It is extremely well done though! The building owner happened to be there and I asked her where she got them. She told me the panels were shipped in from Dubai. She could not say anything more about them.


One last picture of a vertical panel. Check out the identical pointed white crystals of feldspar and the duplications in the quartz matrix. 

More pavement geology to come. I might make it into a mini series of blog posts.