Yellowstone Park, Wyoming - Petrified Tree - postcard by Haynes c.1950s

^{Petrified wood can preserve the original structure of the stem in all its detail, down to the microscopic level. Structures such as tree rings and the various tissues are often observed features.}

^{Petrified wood is a fossil in which the organic remains have been replaced by minerals in the slow process of being replaced with stone. This petrification process generally results in a quartz chalcedony mineralization. Special rare conditions must be met in order for the fallen stem to be transformed into fossil wood or petrified wood. In general, the fallen plants get buried in an environment free of oxygen (anaerobic environment), which preserves the original plant structure and general appearance. The other conditions include a regular access to mineral rich water in contact with the tissues, replacing the organic plant structure with inorganic minerals. The end result is petrified wood, a plant, with its original basic structure in place, replaced by stone. Exotic minerals allow the red and green hues that can be seen in rarer specimens.}

^{Yellowstone National Park (Arapaho: Henihco'oo or Héetíhco'oo)[4] is a national park located primarily in the U.S. state of Wyoming, although it also extends into Montana and Idaho. It was established by the U.S. Congress and signed into law by President Ulysses S. Grant on March 1, 1872.[5][6] Yellowstone, the first National Park in the U.S. and widely held to be the first national park in the world,[7] is known for its wildlife and its many geothermal features, especially Old Faithful Geyser, one of the most popular features in the park.[8] It has many types of ecosystems, but the subalpine forest is the most abundant. It is part of the South Central Rockies forests ecoregion.}

^{Native Americans have lived in the Yellowstone region for at least 11,000 years.[9] Aside from visits by mountain men during the early-to-mid-19th century, organized exploration did not begin until the late 1860s. Management of the park originally fell under the jurisdiction of the Secretary of the Interior. However, the U.S. Army was subsequently commissioned to oversee management of Yellowstone for a 30-year period between 1886 and 1916.[10] In 1917, administration of the park was transferred to the National Park Service, which had been created the previous year. Hundreds of structures have been built and are protected for their architectural and historical significance, and researchers have examined more than 1,000 archaeological sites.}

^{Yellowstone National Park spans an area of 3,468.4 square miles (8,983 km2),[1] comprising lakes, canyons, rivers and mountain ranges.[8] Yellowstone Lake is one of the largest high-elevation lakes in North America and is centered over the Yellowstone Caldera, the largest supervolcano on the continent. The caldera is considered an active volcano. It has erupted with tremendous force several times in the last two million years.[11] Half of the world's geothermal features are in Yellowstone, fueled by this ongoing volcanism.[12] Lava flows and rocks from volcanic eruptions cover most of the land area of Yellowstone. The park is the centerpiece of the Greater Yellowstone Ecosystem, the largest remaining nearly-intact ecosystem in the Earth's northern temperate zone.[13]}

^{Hundreds of species of mammals, birds, fish and reptiles have been documented, including several that are either endangered or threatened.[8] The vast forests and grasslands also include unique species of plants. Yellowstone Park is the largest and most famous megafauna location in the Continental United States. Grizzly bears, wolves, and free-ranging herds of bison and elk live in the park. The Yellowstone Park bison herd is the oldest and largest public bison herd in the United States. Forest fires occur in the park each year; in the large forest fires of 1988, nearly one third of the park was burnt. Yellowstone has numerous recreational opportunities, including hiking, camping, boating, fishing and sightseeing. Paved roads provide close access to the major geothermal areas as well as some of the lakes and waterfalls. During the winter, visitors often access the park by way of guided tours that use either snow coaches or snowmobiles.}

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^{Text from the free encyclopedia WIKIPEDIA may appear below to give a little background information (internal links may not  work) :}

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^{Petrified wood (from the Greek root petro meaning "rock" or "stone"; literally "wood turned into stone") is the name given to a special type of fossilized remains of terrestrial vegetation. 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. Unlike other types of fossils which are typically impressions or compressions, petrified wood is a three-dimensional representation of the original organic material. The petrifaction process occurs underground, when wood becomes buried under sediment or volcanic ash and is initially preserved due to a lack of oxygen which inhibits aerobic decomposition. Mineral-laden water flowing through the covering material deposits minerals in the plant's cells; as the plant's lignin and cellulose decay, a stone mold forms in its place. The organic matter needs to become petrified before it decomposes completely.[1] A forest where such material has petrified becomes known as a petrified forest.}

^{Elements such as manganese, iron, and copper in the water/mud during the petrification process give petrified wood a variety of color ranges. Pure quartz crystals are colorless, but when contaminants are added to the process the crystals take on a yellow, red, or other tint.}

^{Following is a list of contaminating elements and related color hues:}