An October 10, 2012 television program on Nova dealt with Viking swords and their origins. Some of the metallurgical techniques can be traced back to ancient India.
India possessed an advanced knowledge of metallurgy. The pillar known as the Iron Pillar of Delhi, built by Chandragupta II Vikramaditya (375–413), stands at the Red Fort, where it has stood for over 1,700 years, and although made of iron, it has never rusted. No one knows how this could be possible.
The Vikings made certain swords from what was called Damascus steel; imported to the Middle East from India. In India it was known as Wootz steel. The Vikings, as we know, were a warlike people, who made a practice of raiding and pillaging, so swords were important to them. Like many ancient peoples, the Vikings worshipped their weapons. The only way to gain admission to the Viking heaven, Valhalla, was to die…
English: William Morris Davis (1850-1934), American geographer and geologist (Photo credit: Wikipedia)
The cycle of erosion was a model for stream erosion and landscape development proposed by William Morris Davis in the late 19th century. Davis’ Stages in the fluvial cycle of erosion published in 1909 defined a young, mature, and old sequence in the development of river valleys and the landscape the rivers were eroding. His basic concept includes a rapid tectonic uplift, followed by cessation of the land, which allows the rivers and streams to reduce the surface to a level close to sea-level. The concept of peneplanation was a part of his model. In his model Davies picked up ideas of John Wesley Powell about limitation of erosion on land and concluded that sea level is the ultimate base level for sub-aerial erosion. Further he suggested that streams always have at least some gradient and temporary base levels, such as inland-lakes, are controlling points upstream of them. The model developed by Davis, though important in historical context, is currently considered only a first approximation. Developments in the sciences of geology and geomorphology, especially the plate tectonics revolution of the 1960s and 70s, have confirmed the preliminary nature of the model.
The cycle of erosion, as envisioned by Davis, has its initial stage at a time when the landmass is rapidly elevated by internal earth forces, followed by a very long period of tectonic quiescence. Once raised high above sea level as a landmass, streams come into existence and erosion begins to operate on the uplifted mass which is gradually worn down almost to a plain. The landmass may, at some later time, be rejuvenated and the cycle begins again and remnants of the earlier cycle of erosion are preserved at new and higher levels. In a normal cycle three stages have been recognized as: youth stage, mature stage and old stage. These follow each other in a regular sequence.
Youth Stage
In this stage the river flows along an uneven surface and there is intensive bottom erosion, the gradients are steep and the erosion is rapid. The rapid deepening of the channel leads to the formation of V-shaped valleys. Thus during the youth stage of a river, the valley form undergoes vigorous development, particularly in depth and head ward growth. Lakes, rapids, waterfalls, steep-sided valleys and gorges are of common occurrence during this stage. Besides, the phenomenon of river-capture or river piracy takes place in this stage. Youthful rivers have an irregular long profile (thalweg) from source to mouth.
River Capture
When one of the two rivers flowing in opposite directions from a single divide, becomes more effective in erosion due to steeper gradient (when the slopes are unequally inclined), the divide gradually recedes towards the side with the gentler slope. In other words, the river with steeper gradient extends its valley head ward thus causing a shift of the divide against the river with gentle gradient. Gradually deepening of the valley continues head ward with pronounced dissection of the ridge (divide). Sometimes this head ward migration of one river enables it to reach the river on the other side. But, as the first river has a steeper gradient than the other one, the course of the second river gets diverted and its water starts draining through the channel of the first river. This process of diversion of a river by the head ward migration of another river is known as River-Capture or River-piracy. The point where the course of the second river is diverted is known as the Elbow of capture. The captured river is known as Misfit and the deserted part of its channel through which no water flows is termed as the Wind-gap.
Mature Stage
In this stage rivers attains a profile of equilibrium. The land mass is fully dissected and a well-integrated drainage system is developed. Ridges and valleys develop prominently. Flood plains develop and river meandering takes place. The topography consists of features such as: hogbacks, cuestas, mesa, butte, meanders, oxbow lakes, natural bridge, flood plains, alluvial fans etc.
Old Stage
In this stage the slope is gentle and the velocity is low. The river lose most of its erosive power and flow in a sluggish manner. In old age a river has maximum meandering. The river at this age does little of erosion and transportation but is mostly engaged in deposition. This stage is characterised by the development of distributaries and the river flows almost at the base level of erosion. The topography consists of features like peneplains, natural levees, deltas etc. Most of the cycles of erosion do not reach the final stage, as sometime during their operation either climatic or tectonic disturbances take place, and thus results in an incomplete or partial cycle.
The following are my reflections following attendance at this year’s geographical intelligence (GEOINT) conference in Orlando, FL.
If you ask me to identify this year’s key terms in the GEOINT sector, I would identify the following:
Source: GEOINT 2012, David Gauthier (NGA).
Activity-based intelligence (ABI). This was the overall key term and concept by far. According to various speakers, it means focusing on “transactions” that connect entities (often people) and objects over space and time, in real time. Compare and contrast to “situational awareness” in more general terms. Includes “big data” for more efficient “discovery” of significant happenings, “patterns of life,” and networks for what is sometimes called “tipping and cueing” ie noticing something interesting is going on and directing further sensors to stare at that event. (For more on ABI, see the Sept/Oct. issue of NGA magazine Pathfinder, pp. 8-10.)
ISRO plans to launch 58 space missions, including sending spacecraft to moon and Mars, an exclusive satellite to keep a round-the-clock watch on the country and deploy 500 transponders in the next five years.
It also aims to deploy its own version of the Global Positioning System by putting into orbit a constellation of seven satellites which would form the Indian Regional Navigational Satellite System (IRNSS).
According to the 12th Five Year Plan, approved by the Cabinet last week, the Indian Space Research Organisation plans to add 400 transponders to the existing 187 to meet the growing demand from DTH operators, satellite mobile communications and new generation broadband VSAT systems.
The space agency is also designing a special ‘eye-in-the- sky’ — Geo-Imaging Satellite or GISAT – to be stationed 36,000 km above to maintain round-the-clock vigil and assist state authorities to tackle natural disasters, floods and forest fires and keep a watch over the country’s sensitive borders.
Missions initiated in the 11th Plan like Chandrayaan-II, Astrosat-1 and Aditya-1 are also expected to set forth on their respective destinations into space over the next five years.
As part of Chandrayaan-II, ISRO plans to land a rover on the lunar surface and put a satellite in an orbit around the moon. The mission is expected to be launched in 2014.
The wheeled rover will move on the lunar surface and pick up soil and rock samples for on-site chemical analysis and the data will be sent to Earth using the Chandrayaan-II orbiter.
Aditya-1 will be dedicated to solar coronal studies and will contain Visible Emission Line Space Solar Coronagraph — the main payload to study the coronal dynamics.
Astrosat-1 is India’s first satellite dedicated to astronomy, which will scan the universe in x-ray, ultraviolet and visible light bands.
Also part of the 12th Plan is the development of the next generation satellite launcher, the GSLV Mk-III, which will help ISRO put heavier satellites into orbit.
Another ambitious mission is sending a spacecraft to Mars, an initiative announced by Prime Minister Manmohan Singh in his Independence Day speech this year.
“India’s first Mission to Mars during 2013 would be important more from the technological perspective viz. Entire mission design, planning, management and operations, and communication from a distance of nearly 400 million km,” the Plan document says.
ISRO plans to put a satellite in a 500 km x 80,000 km orbit around Mars which will carry nearly 25 kg of scientific payloads on board.
The space agency will also pursue mission POLIX to study the X-ray polarisation from bright x-ray emitting objects during the 12th Plan period.
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