A few years back, my family and I traveled to San Jose for a wedding of a close relative of ours. The venue of the reception took place in a beautiful court side of a country golf club villa. A beauty so exquisite that I figured that this would be a good time to kill 2 birds with 1 stone by using this chance to research on a city that held a lot of meaning for me for an assignment.
To try and understand San Jose and its geological history and the sequence of events, I began observing the area in which San Jose is surrounded in.
As you can see below, this is a map from the site of California Department of Conservation which represents the topography of San Jose. From here, it is easy to see which areas are mountainous (represented by green) and which are of lower elevation (represented by white). When using the site provided by the California Department of Conservation, I noticed that it said that the rocks found in the mountainous areas are from the Cretaceous-Jurassic era. Whereas the area in white, in lower elevation, is from the Pleistocene-Holocene era. At first, I was confused as to how that would even make any sense because according to the Principle of Superposition, that layers of sediment are always older than the one above itself. So how is it possible that older rock from the Cretaceous-Jurassic era is higher in elevation than rock Pleistocene-Holocene era in a lower elevation? Then I realized that it all could be due to erosion. Starting with the movement of plate tectonics, mountains can be formed, in this case it did, causing layers of sediments of rock to be pushed upwards. Then due to erosion by air or water or other natural agents, layers of sediment form the Pleistocene-Holocene era have had plenty of time to erode away, along with many, many other layers, it left to reveal that the current sediment of layer that is from none other than the Cretaceous-Jurassic era.
Another geological event that I would like to map out is a fault line that has displaced a large mass of rock. This can be seen in the images below.
The Hayward Fault line is roughly in the area in which San Jose lies. Using the reference of the location of the fault line on the left, in comparison to what I believe are the displaced rock masses (circled in red), which are form the same time (Pleistocene) and both have similar geographical traits (Older alluvium, lake, playa, and terrace deposits), this proves that the two rock masses were originally one piece.
https://pubs.usgs.gov/gip/dynamic/tectonics.html (Image to the left)
In conclusion, of this small geographical timeline of this little intrinsic part of California, this makes sense of this geological timeline of San Jose. I think that for me, if I wanted to uncover more of the timeline of San Jose, I would have to start from the beginning – Pangea! At this point, everything would be theoretical because no human was alive then, much less have the ability to document this from its millions and millions of years of progress. As the plates move or converge or break apart, it would be possible to see what happens to the part of America that is California. Then once all the plates, especially the North American plate, have shifted to their current position today, it will provide some insight as to how the land of America looked. Then from whatever we have recorded on file, data on the land, the geography of San Jose, California, then it will become much easier to figure out the geological timeline of San Jose. So, to boil it down, if I could, I would request to have more information on what the land of pre-America looked like once it surfaced the water, what the San Jose looked like before fault lines/mountains, and also weather conditions of every day since the land came into existence, to see how natural weather eroded at the land.
I guess that my little quest to understand a beautiful little city has come to a standstill as I wait for a moment for more information . . .
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