Two "salutary" cataclysms

Within a short time, these trees will be exposed to two «Salutary» cataclysms.

It is first a gigantic flood that will uproot from this forest millions of trees. They will be dragged by a powerful river, over a distance of 300kms. During this journey, branches and roots are quite often destroyed. Deposited in lagoons and flood plains, submerged under water, therefore sheltered from the air. In this anaerobic environment the trees will not rot.



Secondly, a volcanic eruption, ejecting not lava, but ash, covering them with a layer of up to 800 meters. Diluted in water with other sediments and mineral components, this "soup" begins to slowly penetrate these trunks.

Depending on their porosity, this mixture of ash and sediments penetrates them in varying amounts, at varying depths, making use of the vascular tissues made up of hollow cells allowing the sap to flow through. Amongst the resinous trees, these vessels are tracheids which are linked to parenchyma, fundamental tissue contributing to the efficient flow of nutrients.



Fossilised trees therefore no longer contain wood, but are now made up of Micro crystalline quartz hydrates. This phenomenon is called silicification, calcedonisation or opalisation. A few cavities are even filled with agate, amethyst or citrine. It is then a Pseudomorphosis.

The main deposit can be found in Arizona's « Badlands », at an altitude of 1800 meters.

225 million years ago « The Rocky Mountains » did not exist. When they were raised, the trees gained altitude with them. Earthquakes broke them into logs of around 1metre long. Whilst exposed to the elements, their surface starts to crack, the percolated fluids and the roots distort them, the air oxides their colours. Those on the surface eventually become sand (arenisation) over a variable period. Those trunks still submerged remain protected. Erosion (wind and rain) reveals the hidden trees during the Triassic period, 800 metres deep.


It is for this reason that most trunks found in Arizona have an oval shape. They have not been petrified whilst upright, but when lying on the ground. Any trees which may have, whilst still wood, been weakened by rot would not have stood the pressure. They are typically found in the shape of a rugby ball.


Silicified wood distorted by pressure



Their colours

The journey of each tree, the state of each trunk, their story is unique, which is what explains how their colours can be so different, even between two trunks found very close to each other on one site, even if originating from the same species: coloration of petrified trees has nothing to do with species.

The chemical components carried by the water mixed to ash, a sedimentary matter solution, gave them their colour, in several stages. Iron for example was first to filter into the tree, which produced the reds (rust). Manganese (purple) and copper (bleu) filtered in much later into the denser parts.

The trunks were impregnated in a succession of stages. The first ones took place in the most tender and porous parts of the wood. The more dense areas, the heart, the knots in the branches have more varied colorations. One could almost say that it is the tree which chose its colours, according to its porosity at the time when various colouring substances flowed.

Trunks found lying at a much greater depth have less colouration than those found nearer the surface. Those from Arizona present very characteristic beautiful reds because the soil in which they were found contained iron, the most common mineral found in the Badlands subsoil.


The main colouring components



red, orange, yellow, purple, brown, black from oxidisation, green from reduction

Uranium :

yellow, green, brown


blue, purple, black

Chromium, Cobalt, Copper: 

bleu, vert





Silicon dioxyde:

white, grey






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