Fossil wood is said to have developed when the plant’s substance was covered in sediment. The wood is shielded from rotting brought on by microbes and oxygen when it is deeply immersed in the mud.
Since the wood is kept in deep water, silica, calcite, and pyrite—original plant material—are replaced by groundwater minerals that seep through the silt.
Even highly costly minerals can seep into wood-like opal. The end product is a fossil formed of the original woody material that frequently displays characteristics of wood, cellular structures, and tree bark that have been preserved.
Probably the most well-known petrified park worldwide is this one. Millions of years ago, the Petrified Forest National Park near Holbrook, Arizona, sprang into being. This was just a lowland with a tropical climate and a thick forest around 225 million years ago.
Rainstorms in the tropics created rivers that carried silt and other debris. It was here that massive coniferous trees, reaching up to 200 feet in height and with a diameter of 9 feet, thrived and perished.
Rich river sediments hid fallen trees and broken branches from these trees. The surrounding volcanoes continued to erupt, covering the area with ash and silica as a result of their multiple eruptions.
Large, dense clouds of ash produced by eruptions quickly covered the region, preventing anything from exiting and, of course, preventing the entry of anything, including insects and oxygen. Over time, groundwater percolated through the sediments and dissolved the soluble ash. The plant detritus was replaced with silica from the dissolved ash.
Petrified wood is produced by this silicification process. Petrified wood has a range of colors due to the penetration of other minerals such as iron, manganese, and trace amounts of silica into the wood. That’s how the beautiful Chinle Formation came to be.
How then was this place found? The entire region was excavated and the rocks on top of the Chinle Formation have eroded away millions of years after the formation of the Chinle Formation.
It was found that the wood here was considerably more durable and weather-resistant than the ash deposits and mudrocks in Chinle. Wood that was removed from the earth’s surface as the ash layers and surrounding mudrocks dissolved.
The park is 146 square miles in size. Although it’s dusty and frequently windy, the 5400-foot elevation keeps it cooler than other desert regions, and grass predominates over cacti and other desert flora.
The main draw here, of course, is the petrified trees, which flourished some 225 million years ago when this region of Arizona was considerably lower, close to the borders of a sizable sea to the west.
In addition to the trees, a variety of fossilized creatures have been discovered here, including clams, freshwater snails, enormous frogs, reptiles that resemble crocodiles, and early dinosaurs.
The logs’ silica crystallized into quartz, but other minerals including iron oxide were frequently added, resulting in incredibly stunning kaleidoscopic patterns and hues.
Because the petrified trees are frequently so beautiful, a whole business has developed around removing them from their original locations and chopping them up to construct bookends, wall displays, and other decorative furniture. Theft from the park has long been an issue; an estimated 12 tons of fossilized wood are taken there annually.