Can Strata Above An Unconformity Be Older Than Strata Below It

I just could not resist this. A paper on sequence stratigraphy in the August issue of Journal of Sedimentary Research by Nikki Strong and Chris Paola discuss just how such stratal relations can develop during the evolution of a passive margin lowstand systems tract. That is a lot of terminology. Passive margins are continental margins that form when plates rift and separate as result of sea-floor spreading. The east coast of the U.S and the west coast of India are passive margins.

These margins are characterized by quite a broad continental shelf. Large thicknesses of sediment accumulates on these shelves over time. These deposits are not one homogeneous body of sediment. Rather they are arranged in packages or bundles of sediment known as sequences. The controlling factor on the deposition of these sequences is the rise and fall of sea-level. Of interest here are fluctuations of sea-level spanning roughly 1-10 million years. These are known as 3rd order cycles and the sequences deposited within are called third order sequences. 2nd and 1st order cycles span larger time frames and 4th and 5th order span much smaller periods.

3rd order sequences have become something of a "working unit" for sequence stratigraphers. They are readily recognized in outcrop and in the subsurface using seismic profiling of basins. They also span a long enough period to record different phases of global sea-level history and basin development. Hence the focus on these sequences.

Several types of 3rd order sequences are recognized depending on what phase of a sea-level cycle they are deposited in. Each exhibit distinctive facies arrangements and stratal relationships (should I call it architecture? :)). Sequences deposited during a sea-level rise are called transgressive systems tracts. Those deposited when the sea-level rise has peaked are called highstand systems tracts. And those deposited during a sea-level fall are called lowstand systems tracts. The study of how these sequences evolve and how they are distributed in time and space is known as sequence stratigraphy.

Right. So as sea-level drops, it eventually exposes the continental shelf and an erosional surface develops. When sea-level rises again drowning the shelf, sediment will get deposited on this erosional surface. Geologists recognize this type of surface as an erosional unconformity. It is also a sequence boundary since it separates older sediment of the underlying lowstand systems tract from the subsequent transgressive systems tract. Knowing this how then can strata above an unconformity be older than strata below it?

It is something of a trick question since the researchers were not concerned with the subsequent transgressive systems tract but the complex evolution of the erosional unconformity. The researchers used an experimental basin at the Experimental Earthscape facility at the Univ. of Minnesota. The basin has a subsiding basin floor and a sediment supply system and these were manipulated to recreate scaled versions of lowstand systems tracts.

When I was doing graduate research in carbonates, modeling of sequences to simulate stratigraphic evolution of basins had gained recognition as a powerful tool which complimented outcrop and subsurface evaluation. Now you can get experimental data by recreating scale models of sequences.

That's cool!

The somewhat counter-intuitive stratal relationships develop because sea-level drop across the continental shelf is not instantaneous. The entire shelf is not exposed to erosion all at once or very rapidly. Instead as sea-level starts dropping, the shallower parts of the basin (think near the coast) are exposed early and an erosional surface develops on the exposed sea-floor. At this time the deeper parts (think shelf edge) are still below sea-level and may be active centers of delta formation.

Eventually on the exposed part of the shelf, i.e on the erosion surface a river valley may form and a fluvial depositional system may develop. Sediment is now accumulating on the erosion surface, while towards the shelf edge marine conditions prevail and deltaic sedimentation continues.

As sea-level continues to drop the erosion surface will get extended and keep overriding younger and younger deltaic sediments in shelf edge areas. But sea-level fall and the gradual exposure of the shelf has spanned so much time (often 100's of thousands of years) that often the very initial fluvial sediments deposited on top of the erosion surface will be older than the youngest deltaic sediments that have been recently overridden by the migrating erosion surface.

This may not come as something terrible new to geologists working in sequence stratigraphy but I thought the use of experimental data combined with a theoretical understanding of sequence development is a pretty powerful way to analyze basin evolution. Will this have any practical relevance when it comes to say correlating strata based on their position relative to a sequence boundary? I don't work in this field so I can't say how important such a result will be. But a work like this does remind us that those squiggly lines you see in a geological column and dismiss as just an unconformity, a time of no deposition, a hiatus when nothing but erosion took place, often have complex, protracted and interesting geologic histories of their own.

Shame That Apollo Doctor Didn't Say Evolution

I caught a CNN IBN show on the excessive use of medicinal drugs and the dangers of over medicating. One segment was on antibiotics and the bacterial resistance to antibiotics. You can listen to the short segment here.

Here's what the reporter said on the effect of excessive antibiotics and not completing the course: You are giving the bacteria a chance to survive and in time they become much stronger and the antibiotics cannot kill them

And Dr. Chatterjee from Apollo Hospital: Bacteria develop resistance to them (antibiotics). Then you have to go for a harder antibiotics and then over a few years you will have no medication for these ailments at all.

I may have missed a few words but what I did not miss was the complete absence of the word evolution.

There can be a real difference in meaning when you say "giving the bacteria a chance to survive and in time they become much stronger" or "bacteria develop resistance" and saying bacteria evolves resistance to antibiotics.

A lot of people I talk to have the impression that saying bacteria survive and develop resistance means that any particular bacterial cell over its lifetime will develop resistance or "adapt" to the antibiotic. Bacteria according to this view "get used to the antibiotic". But that is not what is happening. What is happening is evolution through natural selection.

Any population of bacteria in your body will initially be variable in its response to a particular antibiotic. Bacteria replicate at very short intervals and therefore a lot of mutations are arising in a bacterial population (most mutations are due to errors in copying DNA during replication). Under a strong selection environment such as antibiotic treatment, bacteria that happen to have the right mutation that enables it to resist the antibiotic will dominate the population. Bacteria that don't will die without leaving many descendants. The next generation therefore will be a population composed largely of bacteria which are resistant. Several such rounds of mutation and selection might lead to a population of bacteria fully resistant to the antibiotic. The schematic below shows this well.

Source: Wikipedia

Evolution is not a subject that only helps us reconstruct past events or make sense of fossils or explain the diversity of life. Understanding evolution has real and immediate relevance to several pressing issues we face such as agriculture, animal husbandry, origin and spread of diseases like AIDS and SARS and also how to best set up an antibiotic medication schedule. Understanding evolution let's us plan the antibiotic regimen with the best chance of curing us.

The media and the Apollo doctors missed out on an opportunity to explain that to the people.

Some Examples of Climate Change Illiteracy

Following on the heels of my previous post in which I attempted to put up arguments in favor of human induced global warming, a stark and scary reminder of what I am up against. A couple of example of climate change illiteracy I picked up from the blogosphere.

This one is from Climate Progress and an interview with Barb Davis White a republican who is running for the 5Th Congressional District in Minnesota.

WHITE: My name is Barb Davis White and I’m running for the 5Th Congressional District against Keith Ellison for the United States House of Representatives, which is called Congress.

ROMM: Where are you on global warming?

WHITE: Well, global warming really has not been proven. There are 30,000 scientists, including Al Gore’s professor, from Princeton, who says that we are now in a cooling stage. And ev-every — also every other climate that has been warmed had better grapes.

ROMM: So you don’t believe in global warming and you don’t think that people caused it.

WHITE: No, I think global warming is a scam. I think it’s a scam to put taxes — more taxes on us, and it’s called carbon taxes. Our environment has never been so clean, and if we want to push global warming, let’s push it on China, where the smog is so thick that you almost need a helmet to breathe. Let’s push it on Africa and see how they adapt to it, because they’re not going to.

And from Pharyngula who got it from Diatomaceous Earth. A letter sent to the local paper in Fargo, North Dakota. Is Fargo really this eerie?!!

When God sent the rain on this Earth for 40 days and nights, all this water had to go someplace so the Earth would be dry again.

Remember, God is the Creator and controls the universe.

God tilted the Earth from its original position and caused all the excess water to rush to the poles, and there he instantly froze the water into the ice formations that exist today. Time is ticking down on God's time clock.

With all the nuclear bombs that are made and stored for the fast-emerging last battle, this Earth would burn up when these nuclear bombs are set off.

We are not creating global warming - God is tipping the Earth back to its original position on its axis and thus getting all this ice to get ready to move and extinguish the nuclear destructive fires man will create.

Is this being taught in church or at home.? Where do people learn this? Unbelievable! I have come across the first type of illiteracy i.e. the Barb Davis White type in India, but so far not the second. We can find humor in this but it is a rather depressing example of how a religious fundamentalist education can warp your world view. Have you experienced such extreme views in India?

How Should I Convince Friends About Global Warming

I learned about climate change in geology classes but that was about changes over geological time, about the Pleistocene ice ages and the Eocene -Paleocene Thermal maxima and the Mesozoic warm period and so on. All these had natural causes but I am persuaded by the collective scientific evidence that humans are causing the earth to warm up and will contribute increasingly to global warming over the next few decades. But if someone asks me a very specific question, let's say "Can you tell me if there have been errors in the measurement of CO2 recovered from air bubbles trapped in ice", I won't be able to answer that.

A few days ago a friend emailed me just such an article which accuses scientists of mishandling, misrepresenting and even deceit in measurements and the presentation of climate data. The article is written by a Polish radiologist and well know climate change skeptic Zbigniew Jaworowski. I read through the article realized that a layperson who is not aware of the data favoring human induced climate change might get persuaded that human induced global warming is a fraud. How should I go about making a convincing case that the article misrepresents climate science?

Can I leave aside the specific questions about ice-core CO2 levels, maybe give references that point to original work and then still make broad arguments that show that Jaworowski himself has made very unreasonable assumptions and omitted important facts and that the scientific data is trustworthy. I am going to try doing that. This is a bit like the evolution-creationism debate. I can't answer very specific biological questions like maybe how a particular protein evolved but over the years I have gathered broad arguments in favor of evolution. I have persuaded some of my friends using these broad level explanations of evolution and I am hoping I can use the same kind of arguments to explain climate change.

Right. So here is what I came up with. Feel free to add you own insights and suggestions on how to improve such arguments.

1) Combating the conspiracy theory charge: At the outset Jaworowski plays on people's suspicion of big organizations and huge bureaucracies to imply that the IPCC report on climate change is a political document. He invokes a world wide conspiracy involving the U.N, large global warming research lobbies (which he does not identify) and the U.S government. Yes, the U.S government wanting to politicize climate science to show bias in favor of human induced global warming! This has to be one of the greatest perverse jokes of all. This is a government who for the last 8 years has muzzled its own scientists from presenting the true picture about global warming, has edited scientific reports from its research organizations to convey the impression that the science is still uncertain, and had to be dragged kicking and screaming to admit finally that anthropogenic warming is true. Has Jaworowski been sleeping in a cave?

But is it possible that the report has been manipulated? I have found that many people have the perception that it is the IPCC which was responsible for the science as well. This is simply not true. Research about climate change has been going on for decades in hundreds of labs, universities and research organizations. Scientists have been working on their pet projects, often on very specific topics, sometimes not even asking directly whether humans are causing warming or not. Their research for example may involve improving methods of estimating past atmosphere composition using tree ring data as proxy. As a result we have measurements of past atmosphere CO2 which some other researcher could use to ask a different question. Our understanding of climate change has proceeded by just such hundreds of individual efforts of data collection, measurements and sharing. The IPCC has never commissioned any research. It simply appointed a committee to collate evidence into a report.

2) Meeting charges of deceit and omission head on: Throughout the report Jaworowski accuses scientists of manipulating data, being selective in their presentations and sometimes outright deceit. But I found Jaworowski does pretty much the same. Here is just one example. He says that “It is true that CO2 is the most important anthropogenic [trace] greenhouse gas, but a much more important greenhouse factor is the water naturally present in the atmosphere, which contributes some 95% to the total greenhouse effect.” Now water vapor may be contributing a lot to the total greenhouse effect but this does not explain why the current warming is taking place. The atmosphere is not a homogeneous mixture of gases. It has a layered structure and water vapor is more common in the lower atmosphere. With altitude the atmosphere become drier and colder. The concentration of CO2 is increasing in these high cold drier layers. These layers are absorbing more heat and warming up. The earth is taking in more energy than it is giving out since these cold layers don't radiate energy much. Eventually though some of that heat radiates back to the lower levels of the earth causing warming.

In an effort to convince that the human contribution to warming is at best negligible he fires the following statistics; 97% of emissions of CO2 in the atmosphere come from natural source, humans account for just 3% of emissions. This 3% of emissions are responsible for just 0.12% of the total greenhouse effect. Again reading the figure 3% and 0.12% is enough to persuade many people that human contributions are at best minimal. But that is not how the figure should be read.

What is important is the carbon budget and exchange of carbon between the three big reservoirs, the ocean, the terrestrial biosphere and the atmosphere. The ocean emits about 330 billion tons of CO2 and reabsorbs a little more than that per year. The terrestrial biosphere emits through organic material decay and plant respiration about 440 billion tons of CO2 but absorbs an equal amount through photosynthesis per year. We know that the oceans are gaining CO2 every year and cannot be a net source of CO2. Ditto for the terrestrial biosphere. Humans emit about 27 billion tons per year out of which about 40% are reabsorbed in the oceanic sink. Which means that the only excess CO2 left in the atmosphere is from human emissions. We know this because we can fingerprint human emissions in a variety of ways. This means the correct question to ask is how much of the increase in atmospheric CO2 observed over the last few decades is due to human activity and the answer is not 3% but 100%.

Jaworowski’s claim that humans are responsible for just 0.12% of the greenhouse effect is also misleading. The earth is at a comfortable livable temperature today due to the building up of the greenhouse effect by natural emissions of greenhouse gases over the past 4 billion years. Humans had nothing to do with this historic building of the greenhouse effect. So naturally our contribution today to the total greenhouse effect is going to be very small. What is worrying is that our CO2 emissions henceforth over the next few decades will be making the majority contribution to the greenhouse effect. I won't say 100% because future variations in solar radiation may contribute, but our influence on the greenhouse effect is increasing.

95%, 3%, 0.12% all these numbers can easily confuse but they really mean something different than what Jaworowski is letting on. How is that Jaworowski omits these real implications? And what does that say about his credibility?

3) The past is not always a key to the present: A commonly heard argument and one that Jaworowski also uses is that past climatic changes for example the ice ages were triggered not by changing CO2 levels but by changes in solar radiation and so CO2 is not really an important causative factor in climate change. It is true that the Pleistocene ice ages were likely triggered by natural oscillations of solar radiation operating on a Milankovitch frequency of a 100,000 years or so. But that does not mean that CO2 had no role to play in amplifying and maintaining interglacial warm temperatures. This misunderstanding arises primarily because in ice core data, CO2 increase lags the temperature signal by 800-1000 years. Skeptics play on this and claim that therefore historically CO2 has not been an important forcing mechanism for climate change.

Let’s assume that this is true and CO2 had no role to play in the Pleistocene ice age and interglacial warm periods. Does that somehow change the physics of thermal infrared absorption and radiation? If the ice ages were triggered by changes in solar radiation and did not involve the warming effects of CO2 will certain laws of physics become invalid through disuse? Maybe genes can become nonfunctional through disuse but the laws of physics don’t change. The fact is that increases in CO2 in the atmosphere today will inevitable lead to a more potent greenhouse effect. That is just basic physics and it is not influenced by which forcing mechanism controlled past warming. Climate change can take place through a variety of mechanisms. You have to evaluate episodes on a case by case basis.

4) Can we trust scientists? Why do I believe one group of scientists (a large group) and not a loner like Jaworowski? My belief has nothing to do with whether I believe personally in the IPCC or whether I am chummy with some of the scientists or whether I find them to be virtuous honest citizens. What I believe in is the process of science. Scientific ideas are criticized and rethought, data collected and recollected, experiments replicated, instruments re-calibrated when errors are pointed out. The ideas and data we have today about climate change have withstood the test of peer review and elimination. That is why I believe when the vast majority of scientists tell me that humans have and will continue to contribute significantly to global warming.

But Jaworowski and his ilk don’t participate in this free marketplace of ideas. They prefer ambush marketing. Resort to pot-shots at scientists, circulate documents by chain mail over the internet and confuse people with X Files conspiracy theory yarns. Take a look at Jaworowski’s publication record. All in pretty obscure journals and as the caption says “Two of his papers on climate appear on the website of 21st Century Science & Technology magazine!! And I am supposed to believe him over 2 decades of peer reviewed science?

This is all I have for the moment. There are a few other points I have left out regarding past sea-level changes. Maybe I will tackle those in a later post. If you can point to more references and better explanations do leave behind a comment. As I said these are broad explanations for some misleading statements I noticed in Jaworowski's paper and I am sure climate experts can point out many other problems with his paper. But for now I have a list of references below for some of the specific points regarding climate change.

References:

The gripe that the IPCC report ignores water vapour

The gripe about the lag between temperature and CO2 in ice cores

The gripe about the Mann hockey stick curve

Blog on debunking Jaworowski's criticism of ice core data

Some more articles about ice core data

More on Human Fingerprints of Global Warming

I Finally Made It On The BBC

I mentioned earlier that in May as I munched my way through hot dogs on that mother of all outdoorsy day, Memorial Day, the BBC tried contacting me to take part in World Have Your Say. I missed out on that one. But you cannot keep a good man out for ever. Last night I got a call again and this time I was prepared. Be ready at 6.00 pm GMT I was told. We will call anytime during the next hour. The topic was "Are there places we just shouldn't live" referring to risky places like in the path of hurricanes, earthquake prone zones and flood plains.

I remember during graduate studies in the U.S. in the nineties, soccer was not very high on the list of sports news. ESPN Sportscentre used to announce that highlights of soccer will follow after the break and I used to stay glued to the TV hoping to catch them. Inevitably they used to come on last, almost as an afterthought. Me having wasted an hour, then got to catch a glimpse for a few seconds of some smuck hitting a goal. Total frustration! That's what happened to me yesterday night. The BBC admin told me I would be on soon, and I kept waiting and waiting until 6.56 pm GMT and then I was told to say my 2 cents worth.

My spiel lasted for a grand total of 1 minute something and then the show was over. No response from other viewers no debate no nothing! Bollocks, damn and damn!! The podcast is available for any sucker interested in this sort of thing. It's a long download about 22 Mb. I come on last. I finally got on the BBC. I have spoken.