Petrification EarthCache
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An earthcache inside the Natural Resources Building. Hours are 8-5 Monday-Friday. Parking can be a bit tricky- standard metered parking can be found on Pennsylvania Ave. to the south. Placed with permission of the NRB staff.
The posted coordinates will bring you to the east entrance to the Natural Resources Building. All the information you need can be found inside the entry hall exhibit, and the exhibit just right after going up the small set of stairs.
Petrification is the process by which organic material is converted into a fossil, by way of a gradual replacement of the organic material with minerals. The process take a minimum of 10,000 years to complete. Generally, more durable materials (like bone) are more like to make it through petrification, and opposed to less durable materials like feathers or fur. Petrification is actually made up of two smaller processes, permineralzation and replacement.
Permineralization begins when the would-be fossil enters groundwater with dissolved minerals (such as quartz, pyrite, and numerous others). These minerals fill the pores and cavities of a specimen. One type of permineralization is silicification- where silica (found in volanic ash and floodplains) is aided by water in preserving the specimen. The water removes oxygen, slowing the deterioration of the specimen. The silica fills the pores, gradually replacing the specimen. Pyritization follows a similar process, but uses iron and sulfur rather than silica.
Replacement is when water dissolves the original specimen, which is replaced by the aforementioned minerals. The replacement is complete, down to the microscopic level. Generally speaking, the longer replacement takes, the more accurate of details the fossil will take. This process can use some of the same minerals as permineralization. Many fossils use a combination of both permineralization and replacement, although in rare cases some exist after undergoing only one of the processes.
As wood is a relatively durable substance, is is one of the more common materials to be petrified. It exists as the result of permineralization specifically. However, there is a unique distinction between petrified wood and other petrified specimens. Most other specimens are impressions, resulting in a two-dimensional fossil. Petrified wood, however, results in a three-dimensional fossil. This is the result of when the wood becomes buried, resulting in a full fossil rather than just an imprint.
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To complete this earthcache, please email me the answers to the following questions. Questions 1 and 2 are found in the entry hall, while question 3 is found in the hall to the right:
1) How did the lycopod play a part in the creation of coal beds?
2) How old is the Cretaceous Tree Trunk?
3) According to the "Lycopod Stump" plaque, why are lycopods commonly preserved (relative to other plants)?
4) The Cretaceous Tree Trunk and Lycopod Stump are from Alexander and Franklin counties, respectively- both in southern Illinois. Why would this area have more discoveries of fossils than northern or central Illinois?
(Information source: UIUC ISGS website and Wikipedia)
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