Experience this EarthCache
This Earthcache will bring you to Sawyer Point, a Great Park of Cincinnati along the Ohio River. Here you will follow a geologic time scale set into the walkway, and learn about the generally accepted major events of the last 450 million years.
A Crash Course in Geologic Time
So what makes geologic time different from regular time? Well it goes all the way back to the beginning of earth’s formation 4.6 billion years ago. It is divided into many different segments (called periods) that are marked by major events in earth’s history. Because the earth is so old, geologists think in thousands to billions of years, not seconds minutes or days.
How did this come to be?
The geologic time scale originated from the law of superposition. This word basically means (in terms of rock layers) that in an undisturbed sequence of rocks or sediments, the top layer is younger, and the bottom layer is older. This seems like a pretty basic concept, but once scientists started to notice that fossils changed from layer to layer, they started to figure out that perhaps the rock layers track changes in the earth’s biota over time.
Below is a cartoon showing the different “layers” of time, starting from the formation of earth 4.6 billion years ago. Note: this is not to scale! This is simply a cartoon illustrating the changes in critter assemblages over time. On the right is the name of each time period with its age (in millions of years). On the left is a sketch of what type of life may have been around during that time.
How do geologists assign an “age” to an event?
Since radioactivity was discovered over 100 years ago, geologists have found ways of measuring radioactive decay of elements in certain rocks to determine when they formed. Just knowing a few ages can help because we use the order of the rocks (remember superposition?). If we know the age of the bottommost rock if 1000 years old, the ones above it must be younger, right?
Now, back to your walk through time.
Each block represents ONE MILLION YEARS. How amazing! Each block also has information about the time period represented. The trail is just over 0.25 mile long, and you will start in deep time (450 million years ago). Your walk will help you understand Earth’s geologic history over this time period, and how it relates to Ohio, and all of those fossil-rich rocks you see all around you.
* Source research and text by LtStabos.
Once you log this Earthcache as "FOUND" please message us the answer to the following question within 1 hour.
- Find the Quaternary (Hint: It’s at the very end of the trail). How big is this section?
- Look at the time scale cartoon above. In what ways has life changed from the Cambrian until now? Be very brief, just look at the little critters on the left side. What do you notice about them?
For your GeoTrail Passport you will need to collect the following answer.
- Look at the very first stone of the walkway (450 million years ago). Who is this walk dedicated to?
To access the Earthcaching 101 GeoTour Digitial Passport: CLICK HERE.
EarthCaching 101 GeoTour Locations:
- ECGT A Walk Through Time (GC7P5RE)
- ECGT Rocks of Fountain Square (GC7P5RG)
- ECGT Ohio River Flood Gauge (GC7P5RJ)
- ECGT Very Old Logs (GC7P5RM)
- ECGT Mount Adams Landslide Hazard (GC7P5RN)
- ECGT Cincinnati River Valleys (GC7P5RQ)
- ECGT "Glacial Erratic" (GC7P5RT)
- ECGT Pervious Pavement (GC7P5RW)
- ECGT Forest Avenue Wetland (GC7P5RZ)
- ECGT Cincinnati Fossils and Stratigraphy (GC7P5T1)
DISCLAIMER: With the exception of paid-entry private/large events, this area is open to the public. Access may also be restricted during events. To find out if there is such an event planned at Sawyer Point, visit cincinnati.com or call 513-357-2604.