Argentine Limestone
Whether you're a regular to the area or visiting just to grab this earthcache, something is immediately apparent as you walk the final steps up the sidewalks to the posted coordinates: a seemingly out of place chunk of exposed bedrock sits in the middle of this block, towering over the adjacnet businesses and street. This earthcache will examine the geological nature of the local bedrock as well as how the geological properties of it both helped Kansas City become the major metropolis it now is and how those geological properties almost stymied the city's expansion.
Please note that as this is an earthcache there is no container to be found at ground zero. In fact you never even have to leave the public sidewalk! Rather, you are required to make observations and read this description in order to answer several questions posed by the Cache Owner. Once you have successfully sent your answers into the CO via message center or email, you are able to log this Earthcache as found!
Kansas City Bedrock
To begin our examination of this outcrop, we’ll need to travel back in time – more than 300 million years.
Geologically, earth was in its Pennsylvanian Age, a prolonged period of rock and mineral formation. What’s now the Kansas City metropolitan area was landlocked within the supercontinent Pangea and covered by a shallow, inland ocean. For millions of years, aquatic organisms lived, died, and deposited their remains on the ocean floor. This organic matter combined with chemicals in the water to form very hard layers of stone – limestone. Occasionally the ocean would recede and leave behind massive deposits of mud and silt, which over time would harden into a less dense rock layer – shale.
As the ocean repeatedly returned and receded, the layers mounted. The rocky formation piquing our interest at GZ is a bit of exposed Argentine Limestone. To better understand it, we turn to Richard J. Gentile, a professor emeritus of geology at the University of Missouri-Kansas City. He explains that Argentine Limestone isn’t highly regarded as a source of building material. "The major use was as crushed rock for road surfacing," he says. "Consequently, it was called the 'crusher' ledge by early quarrymen."
How the Geology impacted Human Behaviors
Gentile noted that the Argentine layer, once the source of several springs, is still visible along Cliff Drive and in areas of Westport. "The springs at Westport are now piped under,” he said, "but they once were the source of fresh water for hundreds of people in covered wagons." These springs were essential to providing easy to access fresh and pure water to early travelers which, combined with the confluence of the major rivers nearby, made the Kansas City area a perfect spot to stop, rest, and trade.
In its earliest days, Kasnas City started off as a series of buildings and trading posts nestled on a small limestone ledge next to the Missouri River. This was incredibly important for trade purposes. However, as the city began to expand it was immediately faced with a huge issue - limestone cliffs. The same limestone which provided freshwater springs and made the area an important stopping point for those moving westward also stood in the way of city expansion.
Where the local geology once was advantageous, city leaders now faced the Herculean task of carving a city from the rocky bluffs. Nearly all businesses were situated along the riverfront and reachable only by a narrow road described as barely wide enough for a single cart to pass – the river on one side and towering bluffs on the other. A few paths leading south had been established, but challenges remained. As soon as a bluff yielded, a deep valley would stand in the way. Land would need to be leveled and streets graded if Kansas City wanted to break free from the riverfront.
The work of grading the streets continued for decades. Around 1870, excavation began in the Grand Boulevard area where we see our limestone projection. As development advanced southward, many of the downtown buildings that make up today’s Kansas City skyline were anchored to the underlying layer of Argentine Limestone. While it remains uncertain exactly why the exposed bedrock in question was not graded, several residences and other structures remained atop the escarpment through at least the 1950s and it’s likely that the owners were in no hurry to see their properties razed. While the buildings eventually were cleared, we are left with a bit of Argentine Limestone as a reminder of our geological past, of the natural advantages that helped give rise to a city, and of the hard work which was required to expand the city.
Pictured Above Left: Street grading in progress near Fourth Street and Grand in 1886.
Pictured Above Right: Grand Boulevard facing south, with Argentine Limestone and loess accumulation still visible in 1926.
Questions
- Describe the limestone that you see in front of you in terms of visible texture and colors.
- One of the main reasons the limestone was so advantageous to early settlers was that it produced filtered water springs. Which properties that you described in Question #1 do you see that would make limestone so effective at creating springs?
- The argentine layer of limestone is significantly younger than other sections of limestone bedrock in the city. Do you think this would make the limestone stronger or weaker than other limestone layers?
- Based on your answer to question #3 explain why the geology of the layer led early quarrymen referred to this rock as "crusher" rock.
- Take a photo of yourself or a piece of paper with your name on it near GZ and include it in your log!
Please remember in order to log this as a find you MUST send your answers to the aforementioned questions into the CO. Please do not post answers in your log (even encrypted).
References
- https://kclibrary.org/blog/why-there-large-piece-ungraded-bedrock-grand-between-seventh-and-eighth-streets
- https://www.kcur.org/arts-life/2021-10-27/kansas-city-rocks-take-a-geological-journey-across-the-region
- Rocks and Fossils of the Central United States, with Special Emphasis on the Greater Kansas City Area by Richard J. Gentile
- History of Kansas City Missouri by Theodore Case