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Geological Maps, Serpentine Rocks in the South Bay and Plants by Ronald Horii
I was looking for geological information about the SF Bay Area because I'm interested in how rocks relate to plants. There are lots of geological maps. Here are some: Geologic Map of the San Francisco Bay Region by USGS: https://pubs.usgs.gov/sim/2006/2918/. Geologic Map of California by the California Geological Survey: https://maps.conservation.ca.gov/cgs/gmc/. Geology of San Francisco, CA by the AEG: https://www.aegweb.org/assets/docs/updated_final_geology_of_san.pdf.
Interactive map of the geology of California by the AGI: https://www.americangeosciences.org/critical-issues/maps/california-geological-map.
There is an smartphone app called Rockd: https://rockd.org/.
It provides real-time information about the geology of the area that you are standing on.
What's interesting is where the serpentine areas are. What is serpentine? It's California's state rock: https://www.conservation.ca.gov/cgs/Pages/Publications/Note_14.aspx. Serpentine is the common name for serpentinite, which is a type of metamorphic rock that forms along subduction zones: https://en.wikipedia.org/wiki/Serpentinite. Serpentine rock is high in magnesium and iron, as well as other metals, such as chromium, cobalt, and nickel. It produces soil that is high in these elements and low in plant nutrients, like calcium, nitrogen, phosphorous, and potassium. Many native California species are adapted to grow in this soil, but many invasive non-native plants have a harder time growing in it. That means that areas with serpentine soil are some of the best places to see native plants, where they are less likely to get crowded out by non-native plants: https://openspacetrust.org/blog/wildflowers-and-serpentine-soil/. Some of the native plants only grow on serpentine soil. They are called serpentine endemics, and many are rare or even endangered. (https://cnps.org/wp-content/uploads/2018/03/FremontiaV38.4_39.1.pdf, p. 32) Serpentine only covers about 1.5% of the area of the state, but it supports 13% of the species that are only found in California. Knowing the geology of an area will help with understanding the plants and animals that live on it.
The USGS has geological overlays for Google Earth:
https://earthquake.usgs.gov/education/geologicmaps/
There are different options. This is where you can Browse by Quad: https://earthquake.usgs.gov/education/geologicmaps/quadrangles.php.
Download the KMZ file. Start Google Earth. Open that file. Click on the red square in the middle of the quad of interest. There are different overlay options. The Hillshades and Geology options are shown below.
Google Earth is free. Here are the different versions:
https://www.google.com/earth/versions/
I have the Google Earth Pro desktop version.
The advantage of using Google Earth is that it provides 3D satellite views. It's easier to picture how the terrain matches with the geology. Shown below are examples from Google Earth, using different overlay options. They focus on parks and preserves that have significant native wildflower displays and the rocks underlying them. Note the serpentine areas that are in blue. Knowing the kind of rocks that underlie an area can tell a lot about the plants that can live, but it's not everything. Plants live in soil that's on top of the rocks. That soil can vary. Even on serpentine, if there's enough fertile soil, then non-native plants can thrive. Here's information about that: https://creeksidescience.com/what-we-do/nitrogen/
I was looking for geological information about the SF Bay Area because I'm interested in how rocks relate to plants. There are lots of geological maps. Here are some: Geologic Map of the San Francisco Bay Region by USGS: https://pubs.usgs.gov/sim/2006/2918/. Geologic Map of California by the California Geological Survey: https://maps.conservation.ca.gov/cgs/gmc/. Geology of San Francisco, CA by the AEG: https://www.aegweb.org/assets/docs/updated_final_geology_of_san.pdf.
Interactive map of the geology of California by the AGI: https://www.americangeosciences.org/critical-issues/maps/california-geological-map.
There is an smartphone app called Rockd: https://rockd.org/.
It provides real-time information about the geology of the area that you are standing on.
What's interesting is where the serpentine areas are. What is serpentine? It's California's state rock: https://www.conservation.ca.gov/cgs/Pages/Publications/Note_14.aspx. Serpentine is the common name for serpentinite, which is a type of metamorphic rock that forms along subduction zones: https://en.wikipedia.org/wiki/Serpentinite. Serpentine rock is high in magnesium and iron, as well as other metals, such as chromium, cobalt, and nickel. It produces soil that is high in these elements and low in plant nutrients, like calcium, nitrogen, phosphorous, and potassium. Many native California species are adapted to grow in this soil, but many invasive non-native plants have a harder time growing in it. That means that areas with serpentine soil are some of the best places to see native plants, where they are less likely to get crowded out by non-native plants: https://openspacetrust.org/blog/wildflowers-and-serpentine-soil/. Some of the native plants only grow on serpentine soil. They are called serpentine endemics, and many are rare or even endangered. (https://cnps.org/wp-content/uploads/2018/03/FremontiaV38.4_39.1.pdf, p. 32) Serpentine only covers about 1.5% of the area of the state, but it supports 13% of the species that are only found in California. Knowing the geology of an area will help with understanding the plants and animals that live on it.
The USGS has geological overlays for Google Earth:
https://earthquake.usgs.gov/education/geologicmaps/
There are different options. This is where you can Browse by Quad: https://earthquake.usgs.gov/education/geologicmaps/quadrangles.php.
Download the KMZ file. Start Google Earth. Open that file. Click on the red square in the middle of the quad of interest. There are different overlay options. The Hillshades and Geology options are shown below.
Google Earth is free. Here are the different versions:
https://www.google.com/earth/versions/
I have the Google Earth Pro desktop version.
The advantage of using Google Earth is that it provides 3D satellite views. It's easier to picture how the terrain matches with the geology. Shown below are examples from Google Earth, using different overlay options. They focus on parks and preserves that have significant native wildflower displays and the rocks underlying them. Note the serpentine areas that are in blue. Knowing the kind of rocks that underlie an area can tell a lot about the plants that can live, but it's not everything. Plants live in soil that's on top of the rocks. That soil can vary. Even on serpentine, if there's enough fertile soil, then non-native plants can thrive. Here's information about that: https://creeksidescience.com/what-we-do/nitrogen/
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