La Fontana Del Nettuno is a prominent fountain near the northwest entrance to Palos Verdes Estates. I was geocaching in the area with mojostones and The Druids who jokingly said I should place an earthcache here. Well, here you go! You can blame them for this cache LOL! Be sure to do part of the virtual cache which is also here. And not too far away is a traditional. In addition, there's a benchmark at the base of the fountain (so watch your step).
What is the La Fontana Del Nettuno? It's a 1950s replica of a fountain of the same name that was created in 1563 in Bologna, Italy (photo above of the original). The fountain that is present in Palos Verdes Estates looks to be hundred of years old. In reality, it's hasn't passed the century mark in age. This fountain is made out of marble. But not just any kind of marble. Both the base and the sculptures are made out of Carrara marble which is only mined in Italy. The ancient Romans minned this exact marble and thousands of years later it is still being mined in the region. Each of these marble chunks were transported here from Italy to construct this replica fountain. Below is a map of where the marble can be found in Italy.
Marble is a metamorphic rock. It was formed from a protolith rock which (due to a combination of heat, pressure, and time) changed chemically to form marble. A protolith is a rock that had existed before it was metamorphosed into an entirely new rock. The protolith rock to marble is limestone. Limestone forms in warm shallow marine environments and forms when calcium rich organisms (such as those with calcium-carbonate shells) die and fall to the sea floor. As more and more shells fall to the ocean floor, the weight of the ones above compress it into hard sedimentary rock called limestone. Over millions of years, due to tectonic forces, the limestone is pushed deep in the earth (but not too deep where the rock is completely melted and lost).
With time, heat, and pressure the rock begins to changes chemically. On the molecular level, mineral structure and composition reorganizes. While the overall elements on the periodic table that were present in the protolith rock rarely change, they do become rearranged and form new minerals (even if the composition remains roughly the same). Note this only happens if the rock is remains solid during the entire process. If the rock becomes a liquid, the original mineral structures of the limestone is lost and it would then be classified as an igneous rock once that liquid hardens. Note that liquid rock is technically not a rock because it is not solid. If a rock is melted, cooled, and then hardened, it would be classified as an igneous rock.
Below is a chart of common minerals
Below is a chart of common metamorphic minerals
That said, any fossils or sedimentary structures that existed in the protolith rock are then lost during the metamorphic process. The most common mineral in limestone is by far calcite which is from the calcium-carbonate shells of marine sea life. If this is buried and heated to eventually form marble, the calcite reorganizes from being mostly fossils (shell fragments) to nearly pure calcite. Pure marble rarely exists in nature. Instead, like most rocks, there are impurities. Sand particles, which are mostly quartz, can be metamorphosed into quartzite. Some other common minerals are graphite, which appear grey. Graphite forms when there is carbon present in the limestone. Carbon can come from a variety of sources including remnants of organic life, but it's presence does not necessarily indicate it had to had come from life.
Unpolished marble banding looks like this:
Depending factors of heat, pressure, and time, marble can be of a variety of different grades. The grade of a metamorphic rock is dependent on the lineations of crystal sizes. The more elongated grains are, the higher grade a metamorphic rock is. This is because the longer a rock has spent reorganizing its mineral structure, the more time there is for minerals to develop and grow. Why are they elongated? That's due to the pressure the rock is subjected to due to the depth the rock formed at. Therefore all these factors (time, depth, and heat) matter in the grade of a metamorphic rock.
The orientation(s) of these lineations or bands within the rock can tell us a lot about the principle stresses. For example, the maximum principle stress (called sigma-1 [or σ1]) is typically orientated in the north-south direction. In other words, it is orientated vertically in the same direction as the force of gravity. This makes sense as the weight of the rock above squeezes the rock below. However, if there are tectonic forces involved, it could complicate the orientation of sigma-1. There are other sigmas and orientations of stress, however, sigma-1 is always the orientation of where stress is greatest and therefore has the greatest effect on the orientation of banding, which is usually perpendicular (90 degrees) to this orientation (typically in the directions of sigma-2 and sigma-3).
Works Cited
https://www.sciencedirect.com/science/article/abs/pii/S1296207403001183
https://www.viator.com/Versilia-attractions/Carrara-Marble-Quarry/d26227-a23267
http://geologycafe.com/gems/chapter9.html
https://miningeology.blogspot.com/2015/05/metamorphic-ore-deposits.html
https://sites.google.com/site/gvssixthgradescience/home/rocks-yellow-1/metamorphic-rocks-1
https://sites.pitt.edu/~cejones/GeoImages/6MetamorphicRocks/Marble.html
http://rogermarjoribanks.info/sense-movement-structures-part-1-theory/
TO LOG A FIND ON THIS CACHE YOU MUST ANSWER ALL THE QUESTIONS BELOW. YOU CAN CONTACT ME THROUGH MY EMAIL OR THE GEOCACHING MESSAGE CENTER TO SEND YOUR ANSWERS. ANY INCORRECT ANSWERS MAY RESULT IN A CLARIFICATION RESPONSE FROM ME.
1. "La Fontana Del Nettuno" on the first line of your email AND list all geocaching names of your party so I can match your answers to them. If you all want to learn something, I would prefer each cacher send me individual emails in the spirt of earthcaching.
2. Take a close up photo of the banding of the rock using some sort of scale. Geologists often use coins, GPS', pens, shoes, notebooks, ect. You might want to be creative in what you use for your scale, however, the scale that you choose is entirely up to you. Make sure your photo is close enough to capture bands that can be clearly seen. Upload this photo to your log. Do NOT send me your photos with your answers.
3. Describe the (a) texture(s) and (b) color(s) of the marble.
4. Using the mineral identification charts, name at least one mineral that is present within the bands AND one that is in the matrix of the marble.
5. Describe any weathering, rusting, or corrosion that may be occurring. If nothing is occurring, explain why this may be the case. If there is, explain why you think this is occurring.
6. What do you think causes the difference in color from the sculpture part of the fountain (the center below the statue of David) to the walls and steps around the perimeter? p.s., you can thank mojostones for developing this interesting question :)
7. As the marble is displayed on the steps now (not when it was forming), and based on the average orientation of the banding, is sigma-1 orientated vertically or horizontally? How can you tell? Explain.