Originally posted by KilgoreTrout
Originally posted by Harte
Don't forget the process of subduction. Current and ancient (hundreds of millions of years old) subduction zones cause continents to dip and
Australia bounces up and down like a yo yo, in geological time.
But the thing is, why does it do that? What is it reactive to?
I was reading that the sea levels in the meditteranean. at the peak of the last glacial melt, were rising by about 15 cms a week. I'm not sure of
the rate elsewhere. In geological time, the changes that led to the melt, the effect of such vast redistributions of water, would have also led to
subduction activity to adapt to both external and internal changes to the Earth. As well as volcanic and seismic changes. Given how we now
understand the biosphere to work, however partial that understanding may be, there must have been whole chains of events that however spread over
geological time, would have increased awareness of a sentient species population of the living nature of the planet.
Subduction zones are created when a chunk of continent breaks off and falls into the mantle below.
This usually happens where two plates are coming together.
It takes millions of years for the chunk to drift down throught the semi-plastic mantle. In the meantime, the continents move on. As they drift, they
leave the subduction zone and part ways with the other plate that they were up against for so long.
But the chunk continues to fall, and the subduction zone stays where it is.
The Eastern part of the Indo-Australian plate is currently drifting over such an ancient subduction zone. In fact, a huge swath of that continent is
today under the ocean to the East and Northeast of Australia.
That's why Australia is bobbing up and down (in geological time.)
The other side of the plate - the western side of India, is undergoing it's own subduction as it presses into Asia, forming the Himalayas. Thats'
the locale this thread is about.