Fossil Plant Garden EarthCache
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Located outside the entrance of the Florida Museum of Natural History, the Fossil Plant Garden is landscaped with modern species whose ancestors lived millions of years ago.
Museum admission is NOT required for accessing this area, however parking in the area is limited to those with permits Monday through Friday during the day, a few 45-minute metered spaces or the paid museum parking area ($4/day) directly east of the Harn Museum. Parking is free after 3:30 PM and on weekends and state holidays.
One of the central species within the garden is a large piece of fossilized (or petrified) wood.
How Does Petrified Wood Form?
The process of petrification is not completely understood because researchers have not been able to duplicate the process in the laboratory, where it can be observed and measured. However, specific conditions that must have existed for petrification to occur are known. Oxygen would need to be kept away from the dead plant material to limit decay caused by the growth of bacteria and fungi. Most likely, the dead plant material was deprived of oxygen by being buried by sediments settling in water covering the plants as would happen in floods, mudslides or other natural occurrences that would cause rapid covering of the organic material. Much of the fossil wood found today is a product of ancient river and flood plain environments.
After rapid burial one of three things may happen to a log. It may disintegrate completely and not be fossilized, it may be reduced by compression to a thin layer of coal or it may become infiltrated with minerals and petrified. If petrification takes place, minerals carried by water percolating through the sediments are deposited in the empty spaces within and between cells of the wood. This process is called permineralization and preserves the tissues of the wood in pristine condition! In a process called replacement, minerals may also replace even the cell walls of a log’s woody tissues.
Similar to cave features formed by successive layers of mineral deposits, the process of permineralizaton might take hundreds or thousands of years. Once permineralized, the wood is relatively stable and can survive for millions of years. Such fossils are often discovered by accident when the encasing sediments are disturbed by modern construction, roadwork or mining activity, or by natural erosion.
What Minerals Are In Petrified Wood?
The mineral content of petrified wood is easily identified using a mass spectrometer or X-ray diffraction technology. Silica, in the form of silicon dioxide (SiO2), commonly known as quartz, is the most common replacement mineral. In other cases petrified trees are naturally preserved in calcite (calcium carbonate) or even fool’s gold (iron sulfide). Often traces of other minerals give petrified wood its unique color and characteristics. Iron oxide will cause reds, browns, yellows and earth tones. Copper and chrome oxide create greens, silicates of aluminum produce whites, and manganese dioxide makes black.
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, but abundant in some locations including Yellowstone National Park.
Other species found in the Fossil Plant Garden include plants that are native to present day Florida with histories extending millions of years. Some species are no longer living in Florida. Others survive in other regions and some are extinct. Because plants are sensitive to climate change, the discovery of some of these species at high latitudes indicates significant changes in climate in those regions over time. Each of the plants in this garden has a long fossil history in a wide geographic area.
To claim credit for this earthcache, please email the answers to the following questions to the cache owner through their profile. Please do not post pictures of the information or include any of the information in your log, even if encrypted. The information can all be found on the informational signs located in the garden.
1) What type of tree is the fossilized example here?
2) How old is it?
3) What replaced organic matter in this specimen to allow it to be preserved?
4) When did cycads first appear in the fossil record?
5) How far north were examples of Mexican Sago found?
6) Saw Palmetto fossils have been found in present day England. What do you think that says about the previous climate there compared to today?
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