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A fine example of a Petrified Tree in the Mammoth Hot Springs area of Yellowstone National Park.
Information verified and approval for earthcache received via park administrators prior to “placement.” Answers will NOT be found within visitor center. Please keep in mind that the majority of park staff within visitor center may be seasonal and thus not aware of this earthcache.
Several large volcanoes erupted in and near Yellowstone (Absaroka Volcanics). The eruptions were periodic and primarily spewed molten rock. Rain followed and caused mud and broken rock to stream down the mountainsides. At times the volcanoes were violent and covered the countryside with rocks, cinders, and ash. Sometimes the entire Yellowstone region was covered with volcanic debris. Between eruptions, there were often long periods of quiet, long enough for forests to grow. These forests were later covered by volcanic eruptions, causing the petrified forests seen on and near Specimen Ridge, Mt. Washburn, and Bunsen Peak are examples of Absaroka Volcanics. At the end of this volcanic activity, all of Yellowstone lay buried under several thousand feet of volcanic material. The land must have appeared as a rolling plateau with some streams and some volcanoes appearing above ground. Although the process of petrification is not completely understood, we do know that certain elements are required. First, the tree must be rapidly buried in order to minimize decay of the organic (woody) material. The petrified trees of Yellowstone were buried by volcanic deposits and mudflows associated with volcanic eruptions 45-50 million years ago. Second, there needs to be a concentration of silica in the groundwater surrounding the buried tree. In Yellowstone, silica-rich groundwater soaked into the trees, filling in the spaces between wood cells, and eventually hardening. The actual woody material is still there. Paleodendrochronologists (scientists who study ancient trees) can determine the species of tree by applying an acid solution to thin slices of the petrified material. The acid eats away the silica, leaving the woody material relatively intact. By studying this remaining cellular material, scientists can tell us, for instance, that a particular tree was a redwood. Lastly, erosion must uncover the tree so we can see it! In Yellowstone, glacial ice and the eroding power of running water and wind have uncovered the vast areas of fossil forests. There are undoubtedly many fossilized trees still underground that have not been exposed by erosion.
Despite much study of the Yellowstone Petrified Forests, no animal fossils have been found. Why are animal remains absent from the plant fossil-bearing levels of Yellowstone? Because forests would be expected to harbor a wide variety of animals, some of which would be buried by the successive mud slides, the absence of animal fossils has been a mystery. Volcanic activity could have caused larger forest animals to flee elsewhere, but flight cannot be used as an explanation for the absence of all animal remains because many animals could not or would not leave their forest habitats. Land snails, some amphibians and reptiles, many insects, arachnids, and worms would not escape burial. Immature members of many types would be unable to flee. In addition, bones, eggs, teeth, scales, molted skins, castings, droppings, burrows, etc., would qualify as evidence of animal life. None of these have been found in the fossil forest organic levels during a century of research. Considering that delicate plant parts are excellently preserved, animal remains should also have been preserved if they were present. Only one exception is known. Remains of termites have been found in chambers within the petrified wood. If the petrified trees are standing where they originally grew and if the organic levels are the growing surfaces still intact and undisturbed, the absence of animal fossils is difficult to explain. If, however, the trees and the organic debris making up the soil levels were transported by water, the separation of animals from the plants before burial is much easier to explain.
LOGGING REQUIREMENTS
BEFORE you may log and claim this earthcache as a find, you must first email us your answers to the following questions. Do NOT put your answers in your log posting!
1. How many elements are required for a tree to be petrified?
2. Who studies ancient trees?
3. What is the only “animal” fossil to be found in the Yellowstone Petrified forests?
4. What is the diameter of this sample of Petrified tree?
5. How tall is this sample of Petrified Tree?
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