Fallen coniferous trees from million years ago can be found scattered across the desert of eastern Arizona in the form of petrified wood. Made primarily from quartz, these geological wonders are actually fossils, and are often colored by additional minerals during the petrification process: Cobalt can create greens and blues, iron oxides create reds, browns, and yellows, and manganese can create pinks and oranges, just to name a few.
From Wikipedia :. It is the result of a tree or tree-like plants having completely transitioned to stone by the process of permineralization.
All the organic materials have been replaced with minerals mostly a silicate, such as quartz , while retaining the original structure of the stem tissue. Home » Fossils » Petrified Wood.
Image by the National Park Service. Polished slice of petrified wood: Photograph of a polished cross-section of a petrified log from Arizona. Enlarge the image to see the structure of the wood and even insect borings.
Petrified wood is a fossil. It forms when plant material is buried by sediment and protected from decay due to oxygen and organisms. Then, groundwater rich in dissolved solids flows through the sediment, replacing the original plant material with silica , calcite , pyrite , or another inorganic material such as opal.
The result is a fossil of the original woody material that often exhibits preserved details of the bark, wood, and cellular structures.
Some specimens of petrified wood are such accurate preservations that people do not realize they are fossils until they pick them up and are shocked by their weight. These specimens with near-perfect preservation are unusual; however, specimens that exhibit clearly recognizable bark and woody structures are very common. At the top of the gulley, a "pedestal log" is suspended on a column of Chinle Formation.
When the Chinle weathers away, the log will be lowered to the ground surface. Image by Petrified Forest National Park. Petrified wood: A nice piece of petrified wood representing a limb cross section. This specimen shows the growth rings, cellular structure, and external bark. Specimen is about six inches across. The most famous locality for observing petrified wood is Petrified Forest National Park near the community of Holbrook in northeastern Arizona.
About million years ago, this area was a lowland with a tropical climate and covered by a dense forest. Rivers flooded by tropical rain storms washed mud and other sediments into the lowlands. Enormous coniferous trees up to 9 feet in diameter and feet tall lived and died in these lowlands. Fallen trees and broken branches were often buried by the river sediments. Nearby volcanoes erupted numerous times. These eruptions blanketed the area in volcanic ash with a high silica content.
Rapid burial allowed the plant debris to escape destruction by oxygen and insects. The soluble ash was dissolved by groundwater flowing through the sediments. Stone Story. Take a Hike. Nature Boom Time Videos. Now Playing. Petrified Forest National Park. Up Next. Kelp Forest. Sequoia National Park. Twisting Trees. When this occurs in highly wooded area, such as forests, its called……you guessed it, a petrified forest. There are many petrified forest areas all around the world.
There are about a dozen in the US alone. It is probably the largest area with petrified wood specimens. Specimens of petrified wood from this area are highly prized for their color and because the fine grain of the fossilized rock takes a high polish. Collecting specimens in the park is illegal of course but the area with petrified wood is much bigger than the park.
About million years ago, this area was a covered by a dense forest, with enormous coniferous trees up to 9 feet in diameter and feet tall. Many natural occurrences, such as floods, storms, volcanic eruption occurred.
When the trees fell, they were often buried by the river sediments, and petrification would occur. The ash from the various volcanic eruptions were high in silicate and other minerals, creating petrified wood. Petrified wood can also be enjoyed at home. It can be cut into shapes for making jewelry or polished, as part of a fossil collection. The quality and color of the petrified wood depends on the type of mineral, or minerals, that petrify it. For example, pure forms of silicate minerals, which are the most common minerals in this process, are colorless.
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