Tuesday, September 16, 2014

Cool! 3D Printing In The Geosciences

Geological  Fabrication Laboratory!.. Yes.. the future is already here.

and it is run by Franciszek Hasiuk of Iowa State University. He explains in a short note in GSA Today just why 3 dimensional  printing is so useful especially in the geosciences:

In the geosciences, we struggle with a fundamental problem—we love nature, but its aspects can be truly enormous or fantastically miniscule, very far away or exceedingly rare. Our burden is to overcome these conditions and communicate effectively about nature. With equal ease, 3-D printing can make hand-samples out of subduction zones and foraminifera, Martian topography, and seismic data.

Such models are immediately useful because much of what we need to communicate concerns shape and form (Fig. 1). For these purposes, we can produce inexpensive teaching models on demand, saving acquisition costs while bringing unique specimens to broader audiences. Three-dimensional printing makes the natural specimen the starting point. Digital models can be transformed (e.g., scaled, mirrored, distorted) by an instructor or a student to explore concepts like morphology, vertical exaggeration, or strain. With a little CAD work, we can make flexible fossils to more effectively communicate how organisms, extinct and extant, locomote.

Students might more easily develop a sense of scale from a touchable topography—that they themselves choose and print—that combines local elevation data showing natural and human features. By printing in multiple colors, geological attributes (like geologic formations or geophysical measurements) can be printed over elevation data as a way to better understand a new field area or check field results.

There is more about the applications of 3D printing in understanding rock pore networks with applications in the oil industry this Science Daily article.


Tuesday, September 9, 2014

Remotely India # 7: Mesozoic Domes Of The Kachchh Basin

Remotely India # 7

A recent paper in Current Science (open access) on the geomorphology and tectonics of domal structures in Mesozoic strata prompted me to resurrect this old series titled Remotely India. In these posts I put up a satellite image(s) of an interesting geological feature somewhere in India followed by a brief explanation.

Today's post is on the Kachchh basin in western India. In Mesozoic times this region was a long lasting marine basin in which hundred's of feet of sediments accumulated. Occasionally the sea withdrew and fluvial and lacustrine deposits formed. But most the sedimentary sequence represents marine conditions. Over much of the region the sedimentary strata are horizontal to very gently dipping in disposition indicating very little tectonic disturbance of the basin since the Mesozoic.

At places though these Mesozoic sedimentary rock has been upwarped into domes. These appear as a linear series of blisters in the landscape. The observation that they occur in a linear arrangement is significant and geologists have understood that these blisters and domes occur along mostly east-west trending faults. Map below show the geomorphological and tectonic elements of the region. Red cross is the town of Bhuj.

Source: Kachchh Mesozoic Domes, Current Science 

And this image below is of the Habo dome near the town of Bhuj.

Observations reveal that these domes show an antiformal structure with diverging dips i.e. beds (strata) bending or dipping outwards from the core area.

Here is a series of  domes (Dudhai domes) east of the town of Bhuj.

How did these structures form? Geologists reasoning is as follows: a) The domes don't have corresponding basin like structures, so they did not form through compressional forces buckling the crust into swells and depressions b) the domes occur in Mesozoic rocks on the uplifted blocks of faults but they are not found on the other side of the fault blocks. This suggests that the domes are not "drape folds" formed by vertical movement and adjustment of the sedimentary blanket during faulting. Also supporting the view that faulting did not form the domes is the observation that at places the domes are truncated by faults indicating that this type of structural disturbance occurred much later than the formation of the domes.

Image below shows a truncated dome north of the town of Bhuj

c) there is a close association of magmatic bodies of mafic and ultra-mafic composition with the domes. In some domes plug like magmatic bodies occur in the core of the domes. At places small dykes and stringers of magma are seen to dart from the main magmatic body into the sedimentary beds. This indicates that the magmatic bodies intruded the sedimentary rocks. Based on this the best explanation geologists feel is that these domes formed when magma rose through the crust and impinged the base of the Mesozoic sediments causing bending and doming of the rocks.

When did this occur?  Since Mesozoic times as Gondwanaland split apart into fragments forming the western margin of India, the Kachchh region has been subjected to extensional forces which resulted in several rift type basins forming there. East West trending faults and fracture systems are typical structural elements of this region since the mid Mesozoic.  Radiometric dating says the magmatic intrusions into these sedimentary rocks took place about 68 mya to 64 mya (million years ago).  This was just before and overlapping the Deccan volcanism in the Late Cretaceous which suggests that during magmatic episodes molten material was channelized along older fracture and fault systems of the Kuchchh region resulting in a localization of the domes along faults.

Topographic features, the undulations and swells and mountains that wrinkle the earth's crust form in the variety of ways. Classic orogenic mountains like the Himalayas form when tectonic plates collide and deform and thicken and lift up the earth's crust along thrust faults. Prolonged explosive outpouring of lava can form the beautiful yet deadly mountains like Vesuvius, Mount St. Helens and Mount Fuji. Yet, quieter outpouring of lava like the one experienced during Deccan volcanism can form enormous piles of lava. This pile can later be affected by gentler vertical movements of the crust coupled with differential erosion, forming a landscape of cliffs and gorges as seen in the Western Ghats... and sometimes magma ascends and pushes the crust upwards to form blisters like the domes of Kachchh. Coincidently, David Bressen has a blog post on the history of the idea of plate tectonics. Before this theory explained the origin of large mountain chains, the prevailing view was that mountains are blisters and bumps formed by magma pushing the crust from underneath..!!

Interactive Map:

Monday, September 8, 2014

Quote: Steven Pinker On Education

The Ivy League admissions process comes under Steven Pinker's critical eye. It should be more meritocratic and less "holistic" he thinks. I liked this passage on the role of education:

It seems to me that educated people should know something about the 13-billion-year prehistory of our species and the basic laws governing the physical and living world, including our bodies and brains. They should grasp the timeline of human history from the dawn of agriculture to the present. They should be exposed to the diversity of human cultures, and the major systems of belief and value with which they have made sense of their lives. They should know about the formative events in human history, including the blunders we can hope not to repeat. They should understand the principles behind democratic governance and the rule of law. They should know how to appreciate works of fiction and art as sources of aesthetic pleasure and as impetuses to reflect on the human condition.

On top of this knowledge, a liberal education should make certain habits of rationality second nature. Educated people should be able to express complex ideas in clear writing and speech. They should appreciate that objective knowledge is a precious commodity, and know how to distinguish vetted fact from superstition, rumor, and unexamined conventional wisdom. They should know how to reason logically and statistically, avoiding the fallacies and biases to which the untutored human mind is vulnerable. They should think causally rather than magically, and know what it takes to distinguish causation from correlation and coincidence. They should be acutely aware of human fallibility, most notably their own, and appreciate that people who disagree with them are not stupid or evil. Accordingly, they should appreciate the value of trying to change minds by persuasion rather than intimidation or demagoguery.

I believe (and believe I can persuade you) that the more deeply a society cultivates this knowledge and mindset, the more it will flourish. The conviction that they are teachable gets me out of bed in the morning.

Do read the entire article.

Tuesday, September 2, 2014

Human Evolution - Out Of Africa, Assimilation, Multi-Regionalism

So much has happened in the field of human evolution in the last few years!

Two end member theories have been popular for some time. The Out Of Africa theory says that modern humans originated in Africa around hundred thousand years ago and then spread all over the world replacing local populations of humans from older migrations. On the other hand the multiregional scenario said that modern humans did not originated exclusively in Africa. Rather modern humans evolved from local populations everywhere i.e. eg. modern Chinese evolved from Homo erectus  (which migrated there from Africa several hundred thousand years ago) in China with some gene flow between regions.

That extreme multiregionalism has now been rejected by recent advances in understanding genetic relationships between human populations but in a way so has the extreme Out of Africa version. There is evidence now that modern humans interbred with older regional populations as they spread across the world. This is now termed Out of Africa with assimilation or as "leaky replacement" by some.

Chris Stringer a researcher at the Natural History Museum London writes a good summary of the various theories of modern human origins. It is open access and worth reading.

A short excerpt:

 ‘Modernity’ was not a package that had a single African origin in one time, place, and population, but was a composite whose elements appeared, and sometimes disappeared, at different times and places and then coalesced to assume the form we see in extant humans [6]. However, during the past 400 000 years, most of that assembly took place in Africa, which is why a recent African origin still represents the predominant (but not exclusive) mode of evolution for H. sapiens. Rather than saying ‘we are all multiregionalists trying to explain the out-of-Africa pattern’ [1], it would be more appropriate to say ‘we are all out-of-Africanists who accept some multiregional contributions’.