Sunday, January 23, 2022

Errata : Old Carbon

 Dear Email Subscribers,

A correction to my last post on ancient human footprints from New Mexico. I mistakenly typed their estimated age as 22,0000 (Two hundred and twenty thousand). The correct assigned age in the paper I referred to is 22,000 (Twenty two thousand). 

Saturday, January 22, 2022

Links: Tonga Volcano, Old Carbon, Indian Palaeontology

 Sharing these readings.

1) My first impression of the massive Volcanic eruption in Tonga was the mushrooming ash plume seen in a satellite imagery. Over the days more sensors have captured additional information about this event. When it is safe, geologists will travel to the site to sample the volcanic debris and subject it to detailed textural and geochemical analysis to piece together the journey of magma from its source to its explosive entry on the surface.

Scientific American has a good summary - Why the Tonga Eruption Was So Violent, And What to expect next

2) Debate is an integral part of scientific progress. One common platform to engage in a critique and discussion with your colleagues is the Comment and Reply section in scientific journals. You can submit a note explaining the issues you have about a paper, and it is published along with the author’s response. I am across a good example of this in the journal Science. The topic was the recent announcement of roughly 22,000 year old human footprints from Lake Otero, New Mexico. These dates suggest that humans  were present in North America during the Last Glacial Maximum, a few thousand years earlier than what other data has indicated.

The debate revolves around the accuracy of dating these footprints. Of particular interest here is the problems one can encounter with carbon dating a sample. Living beings have amounts of the radioactive isotope carbon 14 in them in equilibrium with the atmosphere. After death, the amount of this isotope in organic tissue starts decreasing due to natural radioactive decay of carbon 14. Knowing the decay rate and measuring its proportion in the organic material gives us estimates of how old the sample is. But what if the source of carbon is old? For example,  it is from very old groundwater or from the bottom of a lake which is not exchanging gases with the atmosphere? The carbon 14 values in such a réservoir will be very low due to ongoing decay and no replenishment of newly formed carbon 14 from the atmosphere. If organisms consume carbon from such a reservoir (which contains carbon 12 and carbon 13 too) and then are sampled , they will be estimated to be older than they really are. 

The Comment and Reply focuses on this problematic aspect of recognising and correcting for the ‘reservoir age’ of carbon 14. Of pointed importance too is the context and location of collected samples. 

A very informative debate on the nuances of sampling and assigning ages. 

Comment- Évidence of humans in North America during the last glacial maximum

Reply- Evidence of humans in North America during the last glacial maximum

3) I have posted about this topic before. Thé challenges and triumphs of Indian palaeontology very well described by Kamala Thiagarajan in this recent article. 

Why India’s Fossil Wealth Has Remained Hidden

Previously, Sreelatha Menon had written about the lack of importance palaeontology is accorded in the earth sciences and the devastation this neglect is inflicting to palaeontology education, awareness, and research. Her essay is worth reading too; What do you do when palaeontology is itself endangered in India?