On display on the North side of the Pettigrew Museum (1889 Queen Anne home of the state’s first U.S. Senator) is a large specimen of petrified wood. As an Earthcache there is not a container to find, instead we have the opportunity to learn about petrified wood. You are not required to enter the museum to find this cache as everything you need is on the outside of the building. But if time allows, you should check out the museum. They are currently open Monday - Saturday 9am to 5pm, Sunday Noon to 5pm.
After completing this Earthcache you will have a better understanding of:
· How wood is turned into a stone fossil
· How certain elements affect the fossil
· How much does petrified wood weigh
The petrified wood you see on this building originated in what is now the Petrified Forest National Park in Arizona.
There used to be a rock polishing business in Sioux Falls in the late 1880’s. They brought 35 trainloads of petrified wood to Sioux Falls to be cut and polished. This business was the only facility in the nation equipped to handle cutting and polishing petrified wood. This wood was harder than local jasper. It was so hard that 200 pieces of Sioux quartzite could be cut in the same amount of time as a single piece of petrified wood of the same size. There is a link at the bottom of this page to learn more about this local historical business.
The Arizona Petrified Forest was originally established as a national monument on December 8th, 1906 by President Theodore Roosevelt. President Roosevelt stated that, “…the mineralized remains of Mesozoic forests…are of the greatest scientific interest and value and it appears that the public good would be promoted by preserving these deposits of fossilized wood as a National Monument with as much land as may be necessary for the proper protection thereof.” Petrified Forest then became a national park on December 9th, 1962. President Dwight D. Eisenhower first approved the legislation in 1958, but President John F. Kennedy saw it completed in 1962. First protected as one of the world’s most colorful and largest deposits of petrified wood, the park now protects far more including archeology that represents more than 13,000 years of human history.
The end of the supply of the beautiful stone forced the stone works business to close its doors. RF Pettigrew purchased the remaining stock of petrified wood. He used the wood on this house and on the sign at the entrance to the Woodlawn cemetery. (See the additional waypoint)
The petrified wood that is seen here are fossilized tropical conifer trees from the Late Triassic epoch. They are over 200 million years old. They formed when dead trees accumulating in river channels were buried by river sediments. The wood is initially preserved due to the lack of oxygen which inhibits decomposition. Mineral-laden water flowing through the covered material deposits in the plant’s cells. Through a complex chemical process involving heat and pH balance, the minerals (typically Silica/silicon dioxide) from volcanic ash mixed in with the sediments which recrystallized into quartz and replaced the organic material. Traces of iron oxide and other substances combined with the silica to create varied colors in the petrified wood. The result is a fossil of the original woody material that often exhibits preserved details of the bark, wood, rings, and cellular structures. This process can take millions of years.
Most organic matter decays rapidly or is eaten by other organisms; some is buried so quickly that it remains intact and may become fossilized, like what you see here.
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.
Petrified wood is not rare. It is found in volcanic deposits and sedimentary rocks at many locations worldwide. It is especially abundant around coal seams, although many of the wood specimens in these locations are casts and molds rather than petrifications.
The brilliant colors in the petrified logs come mainly from three minerals; pure quartz (silicone dioxide) which is white or clear, manganese oxides form blue, purple, black, and brown, and iron oxides provide yellow, red, orange, and brown coloring.
Following is a list of contaminating elements and related color hues:
· Carbon – black
· Cobalt – green/blue
· Chromium – green/blue
· Copper – green/blue
· Iron Oxides – red, brown, & yellow
· Manganese – pink/orange
· Manganese oxides – black/yellow
Petrified wood can be very brittle and shatter like glass. However, it is as strong as steel. Petrified wood rates between 7 and 8 on Mohs Hardness Scale, with talc at 1 and diamonds at 10. It is also very heavy and weighs between 160-200 pounds per cubic foot.
To qualify for this earthcache, send a message or email via my geocaching profile with the answer to the following questions. Do NOT post the answers in your log. Photos are encouraged but not required! If you’d like to see more of this petrified wood on display, please head on over to the additional waypoint at the Woodlawn cemetery.
1. In your own words, define petrified wood.
2. What color is the petrified wood and which contaminating elements may have caused it?
3. How many logs are standing vertically on the NW corner of the museum?
4. What are the dimensions of the log at the very bottom on the NW corner? (Diameter & Height)
5. How much does the log at the bottom weigh? (Volume x Density ---- Volume= Radius2 x π x Height -- Density can be found in the text above.)
6. How many pieces of local Sioux quartzite could be cut in the same amount of time as a single piece of petrified wood of the same size?
You may go ahead and claim “found it” once you have come to ground zero and gathered all the required info. Please try to submit your answers to me as soon as you can so I can verify your FOUND IT log.
For more information on the history of the Drake Stone Works, click the following link. Click here to read more about the Drake Stone Works