Pre Clovis Tools - American Archaeology and Earth Sciences

Science Friday had an entertaining talk with Michael Collins of Texas State University about the discovery of blades and spear points in Texas that pre date Clovis tools which are thought by many to represent the earliest people in the Americas.

From the transcript:

FLATOW: But why do you go deeper, where some other scientists might have stopped?

Dr. COLLINS: Well, we're working against an inertia, two inertias, really, that one has said for very many years that Clovis was the oldest culture in the Americas, at around 13,000 to 13,200 or 13,300 years ago. And some people haven't gotten over that, in spite of the fact for the last nearly 20 years we have had quite a few sites with strong indications of people being here before Clovis

.

And another thing - and that's improving. More and more people are accepting the concept or are at least willing to investigate it.

The other thing, the other inertia that we have, and it's also improving rapidly and greatly: American archaeology has - grew up in the social sciences. 

And not long ago, the vast majority of practicing archeologists in this country had very little background in the earth sciences and consequently didn't really think about the fact that okay, I have found cultural material here, I'm backing this excavation to Clovis, so that's the oldest culture, I'll just quit here, without thinking: You know, the dirt below that is just a little bit older. Why don't I look at that and see what's in it? There just wasn't that - that mindset was not particularly common. But happily, both of those things are changing for the better.

I find the stuff about the lack of earth sciences background hindering exploration a little hard to swallow. You don't need a background in earth sciences to motivate yourself to poke around in slightly older layers.

Just common sense..and perhaps overcoming the first inertia that a mainstream theory could be wrong.

U.K Geological Society Issues Position Statement On Climate Change

This is a good resource organized in the form of questions and answers on geological evidence for climate change. You will be able to learn a lot about past fluctuations in climate, the establishment of the post-Eocene cooling regime, the Pleistocene ice ages and their causes and the role CO2 has played through geological history, mostly as an amplifier of warming.

The U.K Geological Society also firmly states and although there are natural drivers of climate change, burning of fossil fuels has contributed significantly to the current warming trend.

Read the details here.

Crustal Quartz And Continental Deformation

Fresh from the press a revelation:

Quartz deposits hold key to predicting earthquakes:

..The scientists discovered that quartz crystal deposits are found wherever mountains or fault lines occur in states like California, Idaho, Nevada and Utah.

The Utah State geoscientist said the breakthrough came after repeated testing revealed a correlation between quartz deposits and geologic events that was "completely eye-popping."

Using newly developed remote sensing technology known as Earthscope, Lowry and Perez-Gussinye found that quartz indicates a weakness in the earth's crust likely to spawn a geologic event such as an earthquake or a volcano.

A friend pointed out to me the above news which came in a particularly mangled press version of a study published in Nature by  Anthony R. Lowry and Marta Pérez-Gussinyé - The role of crustal quartz in controlling Cordilleran deformation.

In this post-Japan atmosphere of heightened awareness, hype, hyperbole and sensational claims about earthquakes and volcanoes it is important to set the geology straight.

The paper is behind a paywall and I have not read it, but from the abstract I could gather -

The study addresses variations in the presence of crustal quartz and whether it may influence localization of continental scale deformation due to quartz being weaker than other minerals. The study is on the continental scale and when geologists speak of crustal quartz they mean the mineral that makes up part of the bulk of the rock. Crust with high amounts of quartz would mean crust made up of rocks like granites, granite gneisses and quartz rich schists and quartzites. So variations in the bulk composition of the crust over hundreds of kilometers may influence where deformation occurs and persists over geological time.

Tuzo Wilson imagined the crust being recycled by the repeated opening (rifting) and closing (collisions) of continents, the famous Wilson cycle. This study suggests that such opening of continents may be initiated in quartz rich zones of the crust and these previously rifted and weakened zones are then more likely to break into rifts or deform into mountain belts during subsequent tectonic events thus localizing deformation over many cycles.

The press release though mutates crustal quartz into crystal quartz deposits accompanied by a picture of an amethyst crystal cluster and announces that such crystal quartz deposits may help us predict earthquakes. Crystal quartz deposits and crustal quartz mean different things to geologists. Crustal quartz as I explained above refers to the mineral quartz that is pervasive throughout the crust making up a proportion of the rock mass along with other minerals.

On the other hand the term crystal quartz deposits usually is taken to mean veins cutting across the rock mass or cavities in the rock which are filled with quartz crystals often as pretty faceted forms. These may occur over very small regions of a few hundred meters to a few kilometers or so and sometimes quartz may occur in concentrations that can be mined.

These types of small segregated deposits of quartz do not automatically indicate an increased likelihood of earthquakes in that particular area. At the most they may point to the presence of a fault.  For example fault zones contain fractured rock. Mineralizing fluids containing silica may precipitate quartz concentrations along these fractures. However geologists don't make a leap and announce that an earthquake is likely along that fault anytime in the future based on the presence of these crystal quartz deposits.

Quartz deposits by themselves don't tell us anything about the stress levels the crust is under and whether the fault may slip anytime soon. Independent monitoring of stress levels along faults using sensitive instruments is just beginning to be used in some areas but we are a long way away from using that information to make predictions about an earthquake.

Coming back to the paper...Large continental zones over which the crust has been deformed such as rifts, collision zones or subduction zones are also regions where earthquakes are more likely to occur. We already know that. But while there may be a correlation between crustal quartz amount and such large zones of deformation, that does not translate into specific predictions about where and when earthquakes may occur in these zones. The study certainly does not claim any such advance in our understanding of earthquakes.

I had a thought though about the correlation between quartz rich crustal zones and repeated deformation. Think about the early Archean when continents were forming. What would be the future Indian continent is a collage of several such continental nuclei which welded to each other over the Archean and early Proterozoic. An example is the zone of continental deformation along the Narmada rift in central India which has seen suturing and rifting of continental blocks repeatedly in the Archean and early-mid Proterozoic.

The first location of collision between continental nuclei was not controlled by the presence of quartz but was just happenstance. That initial collision, the zone of suture along which the two continents stuck to each other became the prime zone of weakness in the larger continental block. And during collision that zone likely became richer in quartz as partial melting of the old crust formed differentiated quartz-rich new crust.

This crust because it was weak from a previous collision/deformation event was reactivated during subsequent tectonic events and became even richer in quartz following repeated magmatic and sedimentary differentiation of the crust during each such event.

Is there really a quartz enrichment trend in the Precambrian crust of the Narmada rift? Is quartz rich crust the cause or the consequence of localized crustal deformation? Maybe the relation is different in different settings..maybe there are feedbacks...

Mapping New York's Future 200 Years Ago

Sam Roberts in the New York Times writes on the 200th birthday for the certification by city commissioners of a map by John Randel which subdivided Manhattan island into a two dimensional street grid with rectangular plots on which modern Manhattan arose.

The grid was the great leveler. By shifting millions of cubic yards of earth and rock, it carved out modest but equal flat lots (mostly 25 by 100 feet) available for purchase. And if it fostered what de Tocqueville viewed as relentless monotony, its coordinates also enabled drivers and pedestrians to figure out where they stood, physically and metaphorically.

“This is the purpose of New York’s geometry,” wrote Roland Barthes, the 20th-century French philosopher. “That each individual should be poetically the owner of the capital of the world.” 

Imagining The Atlantic Ocean

A passage from Simon Winchester's - Atlantic: A Vast Ocean Of A Million Stories

The Atlantic is in most places not at all like the Pacific or the Indian oceans - it is not dominated by the color blue, nor is it overwhelmingly fringed with leaning palm trees and coral reefs. It is a grey and heaving sea, not infrequently storm-bound, ponderous with swells, a sea that in the mind's eye is thick with trawlers lurching, bows up, then crashing down  through great white curtains of spume, tankers wallowing though the swells, its weather so often on the verge of gales, and all the while its waters moving with an air of settled purpose, simultaneously displaying incalculable power, and inspiring by this display perpetual admiration, respect, caution and fear. 

The Atlantic is the classic ocean of our imaginings, an industrial ocean of cold and iron and salt, a purposeful ocean of sea-lanes and docksides and fisheries, an ocean alive with squadrons of steadily moving ships above, with unimaginable volumes of mysterious marine abundance below. It is also an entity that seems to be somehow interminable. Year in and year out, night and day, warm and cold, century after century, the ocean is always there, an eternal presence in the collective minds of those who live beside it.

As with many of his other books there is a lot of geology in this one too, but it is evocative passages like these that I enjoy the most.