Tuesday, March 31, 2015

Field Photos: Hillslopes And Landslides Kumaon Himalayas

During my recent trek in the Goriganga valley, I noticed steep hillsides and plenty of landslides. There are a number of geological attributes of this region that makes hill slopes susceptible to fail.

The rocks dip steeply - in this region towards the north. These are medium to high grade metamorphic rocks. They are foliated, that is made up of platy and flaky minerals like biotite, muscovite, chlorite and amphiboles.  Because of this, slabs of rock cleave off the plane of foliation. The picture below shows a phyllitic rock with a pervasive north dipping foliation. You can see large slabs of rock flaking off the surface forming small rock falls.

Some layers of rocks are fractured. The picture below shows bands of calc-silicates i.e. clay bearing limestones which have been metamorphosed. The rocks are shattered by intersecting fractures, and blocks fall off the main body of rock. Something else (tremor, heavy rains) must have triggered this major rock fall.

Sometimes soil, shrubs and tree covered slopes may give way like the one pictured below. Again, heavy rains or tremors may trigger this failure.

Add to these natural properties that make the rocks susceptible to breaking, and hillslopes unstable, is the increase in road building activity. Blasting rock faces with dynamite and bulldozers and heavy vehicle traffic result in constant vibrations and small tremors. We started our trek a little north of Dhapa. The picture below shows roads being hacked out of very steeply sloping hillsides.

 Another view of a rock cut in a precipitous hill slope, with a great backdrop of north dipping high grade metamorphic rocks.

Small landslides and rock falls are common along these road sections. Here is a picture of remediation measures being taking; in this case a stone wall..

A view of a large slump between the villages of Kuri (on the left) and Jimia (on the right).

A view of two landslides with a terrifying look down towards the river Goriganga. The major rock fall in calc-silicate rocks I described above and across the valley, along a road being built between Munsiyari and Milam glacier.

Debris from landslides choke streams and rivers. The picture below shows  ponding in the Ramganga river due to excess sediment brought in by numerous landslides along this stretch of road.

The river bed has to be dredged. Here a channel in the Ramganga river bed has been excavated. Sand miners are also busy at work.

Another look at that scary rockfall in the calc-silicate gneisses, with a rough path through it.

Wednesday, March 25, 2015

Volcanism And The Demise Of Neanderthals

In addition to the many proposed reasons, something more to think about:

From Geology (early edition)-

Campanian Ignimbrite volcanism, climate, and the final decline of the Neanderthals - Benjamin A. Black, Ryan R. Neely, and Michael Manga

The eruption of the Campanian Ignimbrite at ca. 40 ka coincided with the final decline of Neanderthals in Europe. Environmental stress associated with the eruption of the Campanian Ignimbrite has been invoked as a potential driver for this extinction as well as broader upheaval in Paleolithic societies. To test the climatic importance of the Campanian eruption, we used a three-dimensional sectional aerosol model to simulate the global aerosol cloud after release of 50 Tg and 200 Tg SO2. We coupled aerosol properties to a comprehensive earth system model under last glacial conditions. We find that peak cooling and acid deposition lasted one to two years and that the most intense cooling sidestepped hominin population centers in Western Europe. We conclude that the environmental effects of the Campanian Ignimbrite eruption alone were insufficient to explain the ultimate demise of Neanderthals in Europe. Nonetheless, significant volcanic cooling during the years immediately following the eruption could have impacted the viability of already precarious populations and influenced many aspects of daily life for Neanderthals and anatomically modern humans.

Widely varying climatic conditions and resource availability may have hit Neanderthals more than "modern" humans. A number of reasons are given including the ability of "modern" humans to set up long distance networks facilitating exchange of technology and ideas.... Off course some would argue that the Neanderthals  never really became extinct. Their genetic legacy lives on in us. There is no doubt that interbreeding between the two human populations means that Neanderthal genes are with us today, but certainly a way of life, a particular morphology, social mores and perhaps a unique language (s) did disappear.

Tuesday, March 24, 2015

Field Photo: A Bend In A Himalayan River

I took this picture of a meander and a point bar deposit on the road from Munsiyari to Bageshwar along a section of the Sarayu river traversing a section of the Lesser Himalayas. It shows the classic meander landform of cut erosion along the outer bank  and deposition along the inner bank. Land pressure is high in the Himalayas too and the point bar deposit has been cultivated.

Another view of the meander and the point bar deposit.

The cultivated portion of the point bar seems at a slightly higher elevation than the present river channel and I think it indicates that the river has incised a little leaving an older point bar stranded. A younger point bar is developing in front of the cultivated portion made up of gravelly sediments.

Thursday, March 19, 2015

Field Photos: Landscapes And People Goriganga Valley Kumaon Himalayas

Staggering!... is the word that comes to mind with view of sheer rock faces like this one.

The northerly dipping rocks are not sedimentary, but are amphibolite and higher grade metamorphic rocks of the Greater Himalayan Crystalline series (some workers call it the High Himalayan Crystalline series) which make up the hanging wall of the Main Central  Thrust. I hiked through the lower portions of the thrust sheet a couple of weeks ago. The main rock types I encountered were augen gniess, mylonites, biotite schists, quarto-feldspathic gneisses. There is more to the mineralogy and petrology of the GHC. Minerals appear not randomly but in a sequence. I will be writing about that in later post after I've got my head wrapped around some difficult concepts  in metamorphic petrology and Himalayan thrust sheet evolution.

This post is a ramble through the beautiful countryside I hiked through. .. Landscapes and the people of the Goriganga river valley north of Munisyari-

A view from Munisyari looking east- It rained and snowed the first couple of days delaying our trek.

Crossing a Himalayan stream

A house in Lilam village. This village is one of the resting post on the hike towards Milam glacier


The children of Lilam village

Hiking uphill from the Goriganga river

Hot chai with two Kumaoni mountain folks- the cheerful crackle of wood fire and the hot sugary tea is just very refreshing

Conversations with an elderly shepherd

The picture postcard Bui Village

The colorful people of Bui Village celebrating Holi, a spring festival. Local booze flowed freely as did our spirits!

It took us four days to reach this weekend getaway at Paton village

A view from the Paton village temple

 Village Ucchaiti where we spent one night

Hikers break- much needed fluids and trail mix!

A house in the beautiful lush village of Bagankhot

Goriganga!  millennia after millennia.. all those boulders.. all those cobbles, pebbles, gravel... all that sand, mud and clay.. that you wash away... has made Bangladesh

I wish we could have stayed longer. Leaving the Himalayas is always depressing, but next year I am planning another trek, hopefully one that will take me higher up in the Main Central Thrust. Keeping my fingers crossed...

Below: Interactive Google Map of the Goriganga river valley north of Munsiyari-