Geology Lessons To An Astrologer

Once again I find myself writing on a geology topic which has made recent news in the Indian media. I am referring to the belief held by some people that a particular alignment of the moon and planets is the cause of major earthquakes. This belief holds that plate tectonics and the earth's internal stresses play a minor role if at all. Astrology and the influence of the gravitational pull of the moon on our daily lives and now apparently the internal working of the earth is a topic that seems to fascinate a lot of people. The reaction I get when a discussion starts is a lot of head nodding and muttering that "there must be something to this" and occasionally a long confident but utterly nonsensical monologue on geology, gravity, tidal forces and earthquakes. Then how do you explain that the Bhuj earthquake took place during full moon? Coincidence is something that believers seem not to believe in.

I did some more searching for tidal triggering of quakes and found out that there has been some recent work that suggests a relation between tides and ocean tidal loading triggering small seismic shocks, but all these studies indicate that tectonic stresses play the major role and tidal stresses if at all a minor one. Researchers are suggesting that tides may raise the level of stress on faults and cause them to slip sooner than they would have. The earthquakes would have happened without the tides, but the additional tidal stresses may be helping it occur sooner. This is similar to the situation of reservoir induced seismicity, where the column of water in a reservoir may increase stresses on already critically stressed faults causing them to slip. So you cannot explain earthquakes as Mr. Dave is proposing by ignoring the tectonic setup. And in any case the mechanism Mr. Dave proposes for tides causing big earthquakes is not viable.

A while ago DNA had an interview with a Mr. Amit Dave who claims he can predict big earthquakes based on the alignment of planets. I criticized that article and pointed out the many mistakes and misunderstandings about geology that Mr. Dave 's theory was based on. I have gotten no substantive reply from him but he did leave a list of question for me in the comments section. Instead of replying to him in a comment I thought I would write a new post. Below is the list of questions:

A few question to MR.kher

(1) Does moon force depend on the body it is acting?
(2) How such a small force produce 4.5 mtrs of high tide in the oceans?
(3) can we observe high tide and low tides in a bucket full of water? why ?
(4) Does mass and volume of molten lava is more than that of waters in the oceans?
Now some questions to Plate Tectonics
(1) Why there are quakes at other than plate boundaries?
(2) How and why the initial two plates ie Laurasia and Gondwanaland
separated initially ? Due to heat currents or Due to Earth rotation?
Because magma will not solidify at the places where splitting forces are already there how did they separated ?
(1)Why there are major quakes allover the globe ,on different plate on a given date?
(2) Why some months are prone to major natural disasters Like May 2008?
(3)Why some of the major quakes have occured onf
full moon or new moon day. BOth Latur(30-09-1993) and Bhuj 26-01-2001)quakes are on full moon day
(4) How does plate tectonics explains pre shocks ?

It seems like a pretty confused and badly framed set of questions.

I'll lump the first two questions together:

(1) Does moon force depend on the body it is acting?
(2) How such a small force produce 4.5 mtrs of high tide in the oceans?

All objects on earth experience gravitational attraction to the moon. The moon's force is very small, about one ten millionth the gravitational pull of the earth. However, the water in the oceans is not rigid. It flows and the earth cannot hold on to it like it does to the rigid crust. The moon is able to pull at it and this gravitational pull along with the centrifugal force created by the earth's spin results in a piling up of water on the side of the earth facing the moon as well as on the side opposite it. Whether tides are 4.5 meters or less or more depends upon the location of the sun and the moon, the particular configuration of the coastline, depth of the ocean at that location and oceanic currents.

3) can we observe high tide and low tides in a bucket full of water? why ?

And do mentally unstable people become even more insane during full moon? And oh, did you hear about that Olympic swimmer who was dragged to the other end of the swimming pool by a low tide? All these are myths, tidal forces don't affect objects over small distances.

This is the key to understanding why large earthquakes cannot be caused by tidal forces acting alone on earth.

Tides are created not by just the gravitational pull of the moon but due to a difference in the gravitational pull of the moon across the body of the earth. The gravitational forces decrease with distance and so an object on the side of the earth closer to the moon will experience a slightly larger pull than an object at the center of the earth, which in turn will experience a slightly larger pull towards the moon than an object on the side of the earth facing away from the moon. The near side of the earth accelerates towards the moon a little faster than the center of the earth producing a tidal bulge on the near side. The solid earth bulges out only a little, maybe a few cm, but the more fluid water produces a bigger tidal bulge. Now the oceans on the far side are being pulled toward the moon less than the center of the earth. This difference causes the oceans to be "left behind" to form a second tidal bulge as the moon pulls the earth away from the oceans on the far side.

So small differences in the gravitational pull of the moon (and sun) realized across the body of the earth i.e over very large distances causes tides.

Now it is easier to understand why small bodies of water like that in buckets, swimming pools and lakes do not experience tides. It is because the water at different locations across these bodies is at the same distance from the moon and experiences no difference in gravitational pull.

4) Does mass and volume of molten lava is more than that of waters in the oceans?
At any one time the mass and volume of lava being produced is smaller than that of the water in the ocean. His theory of earthquakes depends upon tidal forces acting on molten material and causing it to disrupt the earth's crust. This is what DNA quote's him saying:

The earth consists of a thin upper crust and molten lava, magma. The inner crust is semi-solid and hot. Like tidal waves, this molten lava is also influenced by tidal currents. The moment the high tide pull is more, it breaks open the crust and earthquakes occur. If the crust breaks completely, it results in a volcanic eruption. Dave says the most potent quakes occur when the sun, Jupiter, Saturn, and the moon are in mutual potent positions like 0º, 90º, 180º, and 360º. The two planets change their direction of motion from direct to retrograde from time to time. The gravitational pull exerted on the earth by this movement induces a change in momentum, mass and velocity of the molten lava, creating disturbances.

According to him, in this imagined interior of the earth there is a uniform layer of molten material forming an ocean at depth just like the one on the surface. If the surface ocean experiences tides, then so does this subterranean magmatic ocean. High tides in this magmatic ocean will then exert pressure on the overlying solid crust causing it to rupture. The problem with this fantastic scenario is that the description of the interior of the earth is all wrong. There is no uniform layer of magma at depth. The earth's upper and lower crust is all solid and magma within it occurs as small discrete bodies localized along zones of melting mostly close to plate boundaries.

But wait.., what was it about small bodies of liquid and tidal forces? Yes that's right, the difference in lunar gravitational pull across these local bodies of magma will be small and they will experience no significant lunar tides, certainly not large enough to cause the surrounding crust to break.

Let's now take magma out of the picture. A lot of earthquakes are not associated with magmatism and Mr. Dave's theory fails to provide a mechanism to explain them. Can tidal forces cause solid earth to rupture causing earthquakes? This is not as unrealistic as it sounds. As the comet Shoemaker-Levy 9 accelerated towards Jupiter it broke up into pieces due to Jupiter's tidal forces. What happened was that the front of the comet accelerated towards Jupiter at a faster rate than the far side of the comet. This differential pull across its body caused it to split.

But the moon's gravitational pull is not that strong. Any differential pull due to moon's gravitational force felt by the solid rocks across the earth is easily overcome by the earth's own gravitational pull. Still lunar gravity does cause the solid earth to deform a little (solid earth tides), by just about 2 feet across its diameter. There is just not nearly enough differential gravitational pull across any local region of the earth (the swimming pool or bucket of water principle) which by itself can cause the crust to rupture. Earth tides if they do show a correlation to minor seismicity always act in concert with the regional tectonic stress field.

Now to Plate tectonics part of Mr. Dave's questionnaire

(1) Why there are quakes at other than plate boundaries?
Most earthquakes do take place at or near plate boundaries but there are plenty of examples of earthquakes in mid-plate locations far away from zones of plate interaction. The ultimate cause of these earthquakes can usually be traced to plate boundary stresses being propagated across the rigid crust leading to reactivation of weak crustal zones in mid plate areas. Crustal flow arising out of plate-plate collision zones can also form zones of deformation and earthquakes far away from plate boundaries. The recent Sichuan earthquake is a good example. The figure below depicts crustal flow patterns tracked by GPS measurements across and away from the Himalayan collisional zone.


Source: Continuous Deformation of the Tibetan Plateau from global positioning system data

I've explained how plate tectonics can ultimately explain this pattern of crustal flow, deformation and earthquakes in a previous post. Try explaining this using tidal forces.

(2) How and why the initial two plates i.e. Laurasia and Gondwanaland separated initially ? Due to heat currents or Due to Earth rotation? Because magma will not solidify at the places where splitting forces are already there how did they separated ?

The first part is easier to answer since I didn't really understand the second part! How do plates split apart, example Laurasia and Gondwanaland of Pangea fame. The best answer we have is due to mantle convection cells which bring hot material to the base of plates causing doming, weakening of the plate and finally rifting, eventually splitting the plate into two and creating a divergent plate margin. This mantle upwelling and the resultant decompression of the mantle material lowers the melting point of the mantle material causing melting. The melt does not force the plates apart, rather is a result of the rifting of plates.


Miscellaneous:

(1)Why there are major quakes allover the globe ,on different plate on a given date?
(2) Why some months are prone to major natural disasters Like May 2008?
(3)Why some of the major quakes have occured onf
full moon or new moon day. BOth Latur(30-09-1993) and Bhuj 26-01-2001)quakes are on full moon day
(4) How does plate tectonics explains pre shocks ?

All these can be answered in one thread. It also reveals a little of how Mr. Dave thinks. For example his fixation on dates is due to his blind faith that certain days are special because of a preferred alignment of the moon and planets. That's why his insistence on finding out if there is a relation between plates and dates!

Unlike a particular alignment of the moon and planets taking place on certain days, plate tectonics is not an event. It is an ongoing process taking place all the time, simultaneously all over the globe. The earth's plates are moving in different directions, jostling against, subducting underneath and sliding past other plates. This creates different stress fields on different plates and many times pre-shocks (which is nothing but a small earthquake preceding a big one in the same area) and large earthquakes on the same day. There is nothing special about these occasions. Rocks along faults situated on different plates may just happen to slip on the same day. A chance clustering of such events may make certain months seem more prone to earthquakes, but if one takes a large enough data set things even out.

Finally Mr. Dave left another comment on a previous post :

As you all have agreed that there could be major quakes in September 08 ,or for that matter in any month,why you people hesitate in giving three dates

He wants me to give him three random dates and check whether both of us have the same probability of success or failure. Scoring brownie points over each other using three data points is not how science works. This is his theory. The burden of proof is on him. If he want his work to be taken seriously then he will have to write up his results and present them for peer review. Inviting me to play a game of dice in the blogosphere is not the way to test a hypothesis.

Disclaimer Sept. 17: Contrary to some comments left on this post I did not predict the Sept 17 earthquake which occurred in the Satara district of Maharashtra. Nor did anyone else. Don't let people fool you otherwise. You have to give accurate location information (latitude and longitude) along with a hypothesis in terms of geological forces and stresses acting at that location why an earthquake is likely or imminent. Simply saying that an earthquake will occur on this day and time does not qualify as a prediction. The reason is that there are plenty of earthquakes occurring everyday on earth. On average about 10-11 earthquakes of 6-7 magnitude occur every month, 3 earthquakes of 5+ magnitude occur everyday and more than 20 earthquakes of 4+ magnitude occur everyday somewhere on earth. Without a location and a justification "predicting" an earthquake is easy!! :-)

I'll be writing a larger post on this later maybe in a couple of weeks. Do visit again.

Update: Was September 08 Earthquake Month?

Accessing the Shallow Aquifer Under Pune City

The second phase of the monsoons which normally hit Pune by mid July early August may fail. I read a few days ago that the Pune Municipal Corporation (PMC) fearing a water shortage has plans to tap the shallow ground water aquifer by sinking 500 odd tube wells all across the city. Ground water is available at depths as shallow as 20 odd feet under many parts of Pune city. This shallow aquifer occurs in the basalt lava flows of the Deccan volcanic province. The aquifer has different characteristics which vary laterally and with depth. Dug wells which were an important source of water several decades ago offer the best view of this basalt aquifer and its variability. The image below is of one of the few remaining dug wells in my neighborhood. I have fond memories of this well. During the annual Ganesh festival the family used to come here to immerse the Ganesh idol on Ananta Chaturdashi day. Great to see it still flourishing, providing water for a local garden. The well is located on the talus slope surrounding small hills. The contact between the talus and the basalt is sharp and unfortunately cannot be seen as the upper talus portion is lined. Just below the lined portion of the well, is the basalt which has a slab like appearance. This is due to horizontal sheet joints. Water is stored and transmitted along these joints.


These days you can see the rocks properties of the aquifer at construction sites which excavate huge holes in the ground to put building foundations. The image below is taken at a construction site on flat ground and shows a very different profile than the first example.



The image shows a thick mature soil grading into a highly weathered basalt at the base. This highly weathered basalt forms the upper part of the aquifer. The weathered basalt grades into fresh basalt which may have horizontal joints like the one in the first photo or may be a more dense compact basalt with vertical joints. Its hard to find a location which shows the entire sequence and I have started taking my camera with me in the hope that a big construction site will show the entire aquifer profile. Meanwhile the figure below depicts the typical shallow aquifer system seen in the Deccan volcanic province.


Source: ACWADAM

I think its a lousy and dangerous idea to use this shallow water resource in the manner PMC is proposing to. The corporation simply intends to sink tube wells and install hand pumps and let citizens especially those living in slums access to this water without making any provisions for checking its quality. Unfortunately we know very little about the quality of this water. Likely sources of contamination are leaking and broken sewage pipes and seepage of surface pollutants.The section on groundwater in the environmental status report of the PMC shows that the water has not been screened for the presence of metals, microbes and even fecal matter which is very likely present especially in the groundwater underneath slums which often have no sanitation facilities. Without proper treatment any use of the water in the shallow aquifer constitutes a health hazard.

Pune is luckier than most big cities in India in having an adequate water supply during normal monsoon years. The PMC claims to supply about 200 liters per capita per day. This is much more than most cities in India. There are several big surface reservoirs with capacity to meet projected demands over the next few decades. Pune is growing fast and the problem in recent years has been the delays in setting up water supply infrastructure. Construction of water supply pipelines lags behind buildings, sometimes by years. Suburbs and shanty towns come up either without piped water facilities or with pipes too narrow to supply adequate water, leaving citizens dependent on groundwater which they extract from the deeper aquifer (100 feet or more) or buy from providers who tap it.

But the wild card in coming decades is the reliability of the monsoons. If rains become erratic due to climate change then Pune may be forced into tapping the shallow groundwater system to supplement surface water. This should not be done haphazardly like the current proposal. There needs to be a science backed plan which regulates not only the quality of water taken but also strikes a balance between extraction and replenishment. The deeper aquifer is already showing signs of degrading as unregulated extraction has resulted in an overdraft of several meters over the last decade. That means extraction exceeds natural replenishment with the result that ground water levels are falling year after year. The shallow aquifer if similarly exploited will also diminish quickly as a water resource.

My Five Minutes of Fame As Citizen Activist

I have been profiled in the Times of India, Pune edition. Check out this piece in Times e-paper. You may have to navigate to page 6 of July 25th issue once the e-paper downloads: Switch off at signals, save fuel


Almost a year ago I wrote a series of posts on air pollution and environmental problems facing Pune City. At that time my blog was virtually anonymous. A few friends knew I had started blogging, but the site meter counter moved only occasionally. Still, I like writing about science and I was curious about air pollution in Pune and I kept writing. I really had no expectations about the reach and effect those posts might have. I had underestimated badly the power of the Internet search:

how much CO2 emitted during vehicle idling
bus pollution graphs
comparing diesel and CNG emissions
forest CO2 sinks

These search phrases I can say changed the profile of my blog. I have had several thousand hits on those Pune City posts and hundreds of clicks on the images of the graphs and tables, which have most likely been downloaded. If at least part of the role of a science blog is outreach and education, then I am satisfied with the role my blog is playing. Last month a reporter from Times of India stumbled upon those posts and interviewed me. The article was published today. I don't expect editorial control over the content of the article, but I wish a draft had been sent to me before publishing. The article covers only one of the posts I wrote and I felt a broader coverage of my posts would have helped highlight the entire series. I think its best readers refer to my posts on these topics. Links below:

Part1. Idling and Pollution
Part2. PMT buses and Pollution
Part3. Rickshaws and Pollution
Part 4. Urban Forests and Clean Air
Part 5. Sensing Corruption Remotely
Part 6. Diets, Consumption and Global Warming

I like writing about the city I live in and the neighborhood I grew up in. Being profiled like this is always welcome but I will keep writing about local issues regardless.

First Bird: Another Stupid Science Headline From TOI

From Times of India (TOI) science section another stupid misleading headline: World's First Bird Discovered. Here is an excerpt

In the landmark study, published by the Paleontological Association, experts unveiled an extraordinary prehistoric lizard-like "flying" reptile which lived 235 million years ago. The scientific community believes that birds descended from reptiles 50 million years later making the kuehneosaurs the world's first "bird".

The long-extinct species, which inhabited the warm late Triassic period from 235 to 200 million years ago, was first discovered in the UK.

According to experts, the kuehneosaurs, which grew up to 2 feet, used extensions of their ribs to form large gliding surfaces on the sides of their body.

What has been discovered is not really a creature with true powered flight, but one which used extensions to form gliding surfaces, similar to the present day "flying" squirrels. True powered flight in vertebrates first evolved in the Pterosaurs, which really are true flying reptiles. But that is not what is deeply wrong with this report. This is a classic example of the much discredited but still popular thinking about evolution as a linear process. This mistaken view goes as follows; This creature is a reptile and it flew. Birds evolved from reptiles about 50 million years later than this creature lived. Therefore this creature is the first bird. But evolution generates not a ladder but a tree like structure. Kuehneosaurs and birds occupy widely separate branches on the reptile tree. All branches of the reptile tree did not transform into birds. Below is a phylogenetic tree of the diapsids, the group of reptiles that contain birds.

Source: Tree of Life Web

Kuehneosaurs or the "flying"reptiles which are the subject of this study are an extinct group within the Lepidosauromorpha. Birds on the other hand are a group within the Archosauromorpha. Although they lived and "flew" before birds evolved, Kuehnosaurs do not occupy an ancestral position with respect to birds. The best evidence indicates that birds evolved from within the maniraptors, a group of small carnivorous dinosaurs on a branch evolutionarily distant from the Keuhneosaurs. Every reptile that flew is not a bird. Flight, as has been the case many times in the history of life, evolved independently in the Keuhnosaurs , Pterosaurs and in birds.

I saved for the last another really silly aspect of reporting that is becoming quite common in the Indian media eager - or maybe desperate is a better word - to portray Indian achievements. This is how the report in TOI begins;

A group of scientists, including one of Indian origin, has discovered "world's first bird" that lived 235 million years ago.

The emphasis is mine. Did we need to know that? Does it make the report more believable? Does it make every Indian reading this puff up their chests with pride? I don't know about you but I find it plain irritating and infantile of the media to keep slipping these "Indian" achievements down my throat. I checked the abstract to find out about this "Indian" connection. The paper title reads: “The aerodynamics of the British Late Triassic Kuehneosauridae” by Koen Stein, Colin Palmer, Pamela G. Gill and Michael J. Benton and is published in the July 15th issue of Palaeontology. Ms. Gill comes closest to being the Indian origin candidate most likely having a Punjabi ancestry, but I mean who cares?? Not the author I bet. Instead why not spend a little more time understanding reptilian evolution? TOI just might come up with a more readable news report.

My New Blog Banner Image is Glacier Park

A week ago I started thinking about giving my website a new look (subscribers please click through to the site), more in tune with my geology oriented writings. I started rummaging through my picture collection and found some of my trip to Glacier National Park, Montana. I trekked there a few years ago with friends from my graduate student days. Oh, its going to be quite a leisurely trip I was told. Having not read A Walk In The Woods, having not educated myself on what humans have to endure during a sustained wilderness trek I recklessly accepted the invite. Okay, so I am complaining, I went through pain, but in the end it was a glorious experience.

The picture I have displayed on the banner was at the end of the wilderness section of the trip. Six days before I took the picture I was on the other side of the craggy peaks, and you get an idea of what I am talking about. 70 miles in six days and having crossed Stoney Indian pass at around 8000 feet (see map below) we were at Goat Haunt waiting for the ferry to take us to Waterton. We could have trekked that last section too, but a hot shower was too much to resist and I jumped on the ferry.


Source: National Park Service

Glacier National Park is one of the underrated jewels of the American National Park system. Maybe its the remote location in Montana near the border with Canada, but even in the height of holiday season, there is no sign of the bumper to bumper traffic that plagues Yosemite, Yellowstone and the Smokies. There is a new threat though of climate change and receding glaciers. There were 150 of them in 1850. Today only 26 remain and shrinking fast. The National Park service has some podcasts of climate related research which are worth a listen. I recommend a visit to the park, preferably soon to catch the last of the glaciers. I want to go there again. Maybe on this future visit I will take the time to look at some of the geology.