Himalayan Odds

7 Aug 2010

At www.physorg.com/print200237328. html there is a report on a geological study into the formation of the Himalayas, the movement of the Indian plate into the Asian plate. The Indian plate was subducted and this in turn led to the creation of the mountain chain as it just kept pushing against the other. The Indian plate also included oceanic crust which was pushed down into the mantle. Now, researchers on the high mountains have discovered eclogites and the samples have been found to contain garnet. In turn the garnet contains majorite which is formed under extreme pressure - at depths of up to 200km. This means the Indian crust may have sunk much further into the mantle than computer models have shown - and the study expresses some surprise. The rock is therefore thought to have sunk that deep into the earth - and then re-emerged to be found at 1500 feet in altitude. Apparently, that is not a surprise. Eclogites are metamorphic rocks formed in subduction zones in various mountain belts around the world. Minerals found in eclogites formed under pressure and give geologists a clue to the movement and history of mountain formation.

Remaining with the Himalayas, at www.physorg.com/print200238707.html there is news of another paper, this time in the Proceedings of the National Academy of Sciences which purports to show that some species of frogs were left stranded in the ecological niches when the Himalayas began to form - which took place over millions of years. They became separated from fellow communities (just like species stranded on islands) and adapted, or evolved to their new situation. The creation of rifts and river valleys as the mountains were forced ever upwards, provided novel habitats, and distinctive units. It is thought this might give a fix on the timing of geological events. In particular, the frogs are being used in support of a non-consensus theory that not only did the collision of the two plates push the Himalayas upward but it also caused SE Asia and China to move sidewards. In addition, the Indian plate movement was not a continuous process as the consensus model assumes but proceeded in a series of fits - bursts of movement. Hence, the Himalayas were pushed upwards in a process of steps, and frog species in Tibet, China and SE Asia were also affected by the tectonics of the plate collision. Hence, it may be argued, I suppose, that the frog theory would fit a catastrophist scenario to a greater degree than the idea of continual motion at plate boundaries.