Today was a short, beautiful scootering day. Just before I
left my hotel I was pondering if I should wear my poncho, as there was a low
cloud cover, but I decided against it and that was the correct decision. The
day turned nice and sunny, just about perfect in temperature, and I pondered
why I had been so concerned about the equatorial heat. Of course I was coming
down from the mountains, but how much can the climate change over a few
kilometers?
The landscape was beautiful, mantled in green, and gliding
along in my scooter was a real joy.
I have not mentioned much about the geology of Vietnam ,
largely because everything is covered by greenery and there is little to see.
In the odd bare roadcut, however, I have seen deeply weathered plutonic rocks
with knockers of remarkably fresh granite (a reminder to geologists that hard
rock found in a drill core might not be the sound footing we would like).
Around Dalat I also saw some pretty healthy vesicular basalts that make me
suspect of Neogene volcanism, even though I am not aware of active volcanism in
Vietnam .
In another outcrop I saw a nice tilted sequence of redbeds, so clearly there
has been tectonic deformation in the geologic past (add to that the thick
limestone sequences of North
Vietnam ). Finally, as I approached the coast
I found a healthy and rather extensive batholith. Clearly this land has many
hidden geologic wonders.
Going back a little, after happily driving for a couple of
hours I cam to a very steep mountain front, and in less than 10 km dropped a
good 1,000 m in elevation unto the coastal plain (similar to the way one drops
off the Mexican altiplano from Perote to Jalapa and beyond), and my balmy
temperature suddenly gave way to a furnace-like heat.
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