May 2012 Gallery
65 to 180 Million Year Old Art :: Javanese Petrified Wood
In late Tertiary (Pliocene) times, the region experienced near-perfect conditions for the creation of petrified wood. Until man’s intervention, the region was blanketed by thick tropical rainforest so there was plenty of wood to start with. These forests often develop on the flanks of volcanoes that occur along the “spine” of the country from Sumatra in the northwest toBaliand beyond in the southeast. It is this close proximity of forests to volcanic activity that was so conducive to preservation of the wood.
Periodically the various volcanoes erupted in much the same way as didMount St. Helensin 1980. Trees were blown down by the force of the eruption and encased in scorching volcanic ashes. If the trees were too close to the volcano, they were simply incinerated. Too far away, and the trees were not totally covered by the volcanic ash and with time they consequently rotted away in the normal way. However, in the middle of these two extremes, the trees were buried by thick ash which was so hot that it effectively sterilized the trees, destroying all the microbes that normally cause wood to rot.
The volcanic ash has another important function in the generation of petrified wood. It is rich in silica minerals, and the fluids percolating through the ash would also have been saturated with these minerals. The fluids seeping through the ash slowly dissolved the original organic matter of the tree, atom by atom, and replaced it with various silica-rich minerals such as quartz, chalcedony, and jasper. The preservation is so fine that in places you can see the cell structure of the original wood.
The beautiful and varied colors come from trace elements that are dissolved in the silica. Traces of iron, for instance, impart the shades of brown and amber, while manganese oxides produce the blacks and blues. Growth rings are less well developed relative to deciduous trees due to the lack of seasons in a tropical climate, while the large cell structures reflect the moist conditions in which the tree originally grew.




![GREENPOD [Combined]](http://joglonorthwest.files.wordpress.com/2012/04/greenpod-combined.jpg?w=762&h=1024)












