Tuesday, November 28, 2023

Volcanic Versus Human Carbon Dioxide Emissions

A couple of weeks ago Iceland awaited with much anxiety as magma made its way to the surface. A volcanic eruption seemed imminent. That danger seems to have passed for now. Seismicity has abated and magma may not break through and erupt.

Misunderstandings regarding climate change though shows no signs of receding as this comment shows - 

 Source: X - https://twitter.com/dremtee/status/1723427183182446871

Ever so often it is worth putting up the numbers:

Anthropogenic CO2 emissions - About 40-50  billion tons per year.

Volcanic CO2 emissions - Approximately 500 million tons per year.

Terry Gerlach of the U.S. Geological Survey has compiled global data on volcanic emissions  -  Volcanic Versus Anthropogenic Carbon Dioxide, published in EOS Transactions American Geophysical Union. 

This article is from 2011, but there are good explanations on volcanic emission rates and the observed discrepancy (which has increased in the 12 years since publication) between anthropogenic and volcanic emissions. 

What conditions limit volcanic CO2 emissions on present day earth? 

On average, magma contains about 1.5 weight percent dissolved CO2. Estimated annual magma production on earth amounting to about 80 billion tons won't create near enough volcanic CO2 to match human emissions. About 850 cubic kilometers of magma would be needed to be generated annually to create volcanic CO2 on an anthropogenic scale. So much magma production either under land or sea would not have gone unnoticed. 

Short lived volcanic eruptions like past events in Iceland, or Mt. Pinatubo, or Mt. St Helen's, although violent and spectacular,  didn't emit more than a few million tons of CO2. These amounts are too small to have a discernible warming effect. Large explosive eruptions in fact might cool the earth by a degree or so for a short time because the sulphur particles they emit reflect sunlight back in to space.

Can volcanism cause global warming? Yes, but over much longer time scales. 

Weathering of surface silicate rocks consumes about 500 -700 million tons of CO2 per year, offsetting the amount emitted by volcanoes. There has to be sustained volcanism at high emission rates for decades to hundreds of years to create an imbalance between weathering and volcanism and change climate. 

Cin-Ty Lee and Slyvia Dee 's  commentary on this subject explores the role of volcanism on global climate. 

Wednesday, November 15, 2023

River Nira Meander

 So near Pune, yet I had never been to this location near Bhor.

It is popularly known as necklace point. The river Nira loops its way through the countryside forming a series of lovely meanders. A high point overlooking the valley allows a clear view of this feature. 

I was on a drive with some friends, spending the day exploring the back waters of the Bhatgar and Nira Deogarh dams. We eventually reached Warandha Ghat, one of the spectacular passes linking the Deccan Plateau with the western coastal plain. 

At the edge of the plateau, high relief exposes sheer rock faces. 

The grand scale of Deccan Volcanism is manifest so clearly in the lava flows traceable over hundreds of meters despite the afternoon haze.

On a satellite image, X marks the view point looking south towards the big meander.  

This is a beautiful area near Pune to spend a day out.