The posted coordinates take you to an exhibit housed at the Sampson Hoffland Laboratories on the Luther College Campus in Decorah. Parking coordinates have been provided. To get the coordinates for the final cache location, you will need to gather some information at the exhibit and answer some questions.
Note: The building is open every day at 7 am. The lights in the display are turned off at 6 pm on weekdays and 8 pm on weekends. To get to the exhibit, you will need to enter the building and go to the hall on the right. The exhibit is housed in a large case on a corner in the hallway.
A local resident geologist, Jean Young, was working for the Iowa Geological Society. As she was mapping the St. Peter Sandstone in the area, she studied the local well-drillings. In those drilling samples, she noticed a layer of shale, which is unusual for this area. Jean wondered if this layer of shale might be from an impact event. Following further testing, a layer of shocked quartz (shattered crystals) was found under the shale, confirming her suspicions. This area was hit by a meteroite causing a crater about 4 miles wide!
The impact event happened during the Ordovician Period, about 465 million years ago. North America was mostly covered by an ancient sea at that time. Geologists think that when the meteorite slammed into earth, seawater rushed into the newly formed crater pulling with it the blasted material and sea creatures. The low-oxygen atmosphere in the water found deep in the crater helped preserve the creatures’ remains. Over millions of years a mixture of mud, sand and sediments deposited on top increasing the pressure and temperature, compacting the sediment, to form shale containing these preserved fossils. Through thousands of years the Upper Iowa River has eroded away sediment above the outer rim of this shale layer.
The Upper Iowa River near the town of Freeport, on the eastern edge of Decorah, contained the only exposed shale in the area. In 2010, after temporarily diverting the river, geologists dug down about 12 feet and hit the outside rim wall of that crater. There they discovered over 5,000 plant and sea creature fossils, including the oldest known fossils of jawless fish. These fossil discoveries have given geologists new insight into what life was like during the Ordovician period.
One of the most impressive fossils found was a giant sea scorpion. This newly discovered species was later named "Pentecopterus decorahnesis" in honor of Decorah. The 6-foot scorpion with tentacle-like appendages, predated the earliest known scorpion by 10,000 years.
On display here is a 3-D model of what Pentecopterus decorahnesis, the Giant Sea Scorpion, might look like based on the fossil discovery. The actual fossil is being housed and studied at the University of Iowa.
To get the coordinates to the final cache location, gather some information from the Exhibit and the Crater Creation sign in the window:
N 43 19.ABC W 91 48.DEF
A. The number of samples of Winneshiek Shale found in the display
B. What was the diameter of the meteor? Use the first digit
C. The number of short conical brown things hanging down from the ceiling in the display.
D. About how many feet below ground does the deepest point of the crater lie? Use the first digit
E. Middle digit: P. decorahensis lived about 465 million years ago - that's "2 __ 9" million years before the first dinosaur (round black sign)
F. The number of miles per second the meteor was traveling.
You can validate your puzzle solution with
certitude.
Permission to place this cache was granted by Laura Peterson, Head of the Geology Department at Luther College.