Petaluma Wetlands


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Field Assignment
Geology 103
Professor Lawler

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Petaluma Wetlands

  1. 1. Petaluma Marsh/River Area
  2. 2. (www.,_California)This is an aerial view of the town of Petaluma, California. It is in Sonoma County, about 40 miles northof San Francisco. You can see the Petaluma River which runs through town. In the back ground are theSonoma Mountains, which are east of Petaluma. The wetlands area is at the top of the picture.The Petaluma River is not really a river. It is a tidal slough. The town was able to call it a river to getgovernment money for dredging ( so that the debris and silt that builds up from therains and run off can be removed. This prevents flooding and allows boats to travel without hitting thebottom. The Petaluma River is a tidal slough because it is affected by the oceans tides. I have seen thewater in the river so low all you could see was mud and so high I thought it would flood the downtown(Wetlands, 2009).On the website at I learned that the Sonoma Mountains,which are between Napa and Sonoma County, are three to five million years old. The biggest mountainwas a volcano.
  3. 3. The area that I observed is on the southern edge of Petaluma. It is a wetland area, a tributary, where theAdobe Creek runs into the Petaluma River. The River Heritage Center in Petaluma describes this area asthe Petaluma Marsh/River area. On their website at learned the Petaluma Marsh/River area “is the largest remaining intact tidal marsh within the SanFrancisco Bay Estuary”. Information on this website states the marsh/river area is composed of 5,000acres of wetlands ecosystem. 12 miles of the Petaluma River run through this area and empty into theSan Pablo Bay. Ducks, egrets, herons, bats, 25 species of fish, burrowing owl, ferruginous hawk,salmon, Dungeness crab and many other living things are found in this area. There are mudflats, ponds,and marshes. I saw grasses, reeds, flowers, lots of birds, very few rocks, mountains in the background,and butterflies.About 10 million years ago this area and valley was covered with ocean water that was not very deep.The California coast was and is an area with many tectonic faults. As the faults moved the earth thecontinent shifted. Mountains were pushed up and valleys were created. About three to five million yearsago, when the Sonoma Mountain range was formed, this area of marshes and wetland was 1,000 feetdeeper than it is now (Chavez, 2002).
  4. 4. This is a picture of Adobe Creek. The water is very muddy. There are no real banks. Along the banksis what looks like grasses to me. The water is not pretty. I remember, from high school, that studentshelped restore this creek and bring back the Steelhead Trout. In 1982 the creek was dried up, full oftrash and almost dead. It has been cleaned up and restored which helped save a species of steelheadtrout from becoming extinct (Petaluma Visitors Center, 2009). The creek starts from the SonomaMountains in the east and runs into the Petaluma River which opens up into San Pablo Bay. San PabloBay is really just the northern portion of the San Francisco Bay and opens out into the Pacific Ocean.The area I observed which includes Adobe Creek is a tributary. It is a stream that flows into a river andcarries the water from the Sonoma Mountains. Also the area is a tributary because the Petaluma Riverflows into a bay which takes the surface water out to the ocean. Adobe Creek would have evolved afterthe Sonoma Mountain range was created – 3-5 million years ago – as a way for the water from themountain to drain down and out into the ocean.
  5. 5. This is what I observed to be a pond south of Adobe Creek. There are lots of birds and grasses. Whenyou walk around the pond there is an area where you see a marsh and the Petaluma River. I thought thiswas a natural pond but at the Audubon Society website I learned this is where the dredged material fromthe Petaluma River is placed Before the dredged material was put here it was a wetland where the waterfrom the Petaluma River would go when it over flowed (Chavez, 2002; Madrone Audubon Society2004).
  6. 6. Common TuleScirpus acutus occidentale – Common Tule variety occidentalisSpecies Schoenoplectus (bulrush) Family – cyperaceae (sledges) Class Liliopdida Monocotyledonous(flowering plants) Superdivision Spermatophyta (seed production) SubKingdom Tracheobronta(vascular Plants) Kingdom PlantaeaA Perennial herb, native to California( is a picture of what I thought to be a kind of grass. It was growing in the pond, along side, intoAdobe Creek, and all over the wetlands area. In order to identify the plant I researched names of plantsfound in this area. I learned that tule plants need water year around, grow in wetlands areas and fit thedescription of the plants I observed ( I could see that the ends of these plants oncehad something that flowered. Now the ends had what was left of a dead flower. The photo of theCommon Tule (Scirpus acutus) best matches what I observed. The Common Tule is described as abulrush and “native to freshwater marshes, lakes and stream banks throughout lower elevations inCalifornia and much of North America” ( of the Common Tule: The plant kingdom evolved from algae’s. In the Paleozoic Era, around410 million years ago the first vascular plants appeared. The first seed plants appeared about 360million years ago, and flowering plants in the Cenozoic Era, about 130 million years ago. The CommonTule is a sedge or from the family of cyperacae which evolved from flowering plants. Sedge stems areusually solid and triangular in cross section. The stems are long and leaves are flat. They grow to fourfeet in shallow water and spread by tubers or rhizomes that grow underground (Cattails, 2010).
  7. 7. Coastal Tidy TipsKingdom Plantae Subkingdom Tracheobionta Subclass Asteridae Order Asterales Family AsteraceneSpecies Layia Platyglossa (Tidy Tips)( flower is growing all over the land surrounding the Adobe River and marshes. The petals areyellow in the middle and white around the edges. I identified the plant on the website are many kinds of Tidy Tips. This species is native to California. The Platyglossa is a coastalTidy Tip. They are from the Aster family. They evolved from vascular plants that produce seeds andflowers (Tidy Tips/
  8. 8. This is a Black-Necked Stilt. I saw several of these birds in the pond. They have white bellies and ablack back and head. Their legs are really long and pink. I watched them eat from the bottom of thepond. Their scientific name is himantopus. They are a shorebird. Their species is humantopushumantopus mexicanus. They come from the family called recurvirostridae which are all wading birdswith extremely long legs, small heads and long slender bills. Mostly this group is either stilts or avocets.They fall into the Order category as charadriiformes which are birds that fly, live in open country orwater, nest in the ground and feed on animal matter found in or near water. They are in the Class ofAves. Aves are warm-blooded, beaked vertebrates covered with feathers and who have wings( Evolution of the Black-Necked Stilt. The evolution of birds is thought to go back to the JurassicPeriod. There are different ideas about their evolution but the theories I read about link them to reptilelike prehistoric animals. A fossil was found in Germany which is called Archaeopteryx and is prehistoricdinosaur with wings. There are different theories about the exact evolution of birds. Dinosaurs, reptilesand fish fossils have been found with characteristics of birds, including the wings. Modern bird fossilsgo back to the early Tertiary period (Origins, 2007).
  9. 9. Mute SwanIt is not a native bird to the area. The swan’s tribe is Cygnini. The Mute Swan originated in northernand central Eurasia. They are all white, their bill orange, neck long, and feathers are white. Their chicksare gray and white ( They come from the family of Anatidae which are geese, ducksand swans. The class is Aves or modern birds ( They are found in most parts of the world.Most likely they were brought to North America by people. Their ancient evolution is the same as theBlack-necked Stilt.
  10. 10. RocksDuring the end of the Pliocene Epoch, about two million years ago, volcanoes erupted. The lava fromSonoma Mountain hardened into igneous rocks. Most of these are granite rocks. Basalt is found in theSonoma Mountains. Another common rock, formed from the erosion of older rocks and material thatwashed off the mountains, was sedimentary rocks. The erosion of gravel turns into conglomerate rocks,sand into sandstone rocks and clay into shale. When sedimentary or igneous rocks are buried deep inthe earth they become metamorphic rocks. Metamorphic rocks are not found in the area I amdescribing. Rocks in this area are also moved by tectonic movements (Ford, 1975).There were not many rocks to found in this wetland area. I found these on the shore off an inlet pool ofwater next to the Petaluma River. They are light grey with white lines and spots. The rock is very hardand mostly smooth. There are white grains. This rock has characteristics of granite: fine grained, neartectonic plate and area of mountain building. It has grains which are rocks from an earlier date (Monroe,2009).
  11. 11. There were many of these rocks in all sizes on the banks of the pond. The rocks are notas hard as the granite and look similar to the cracked mud bank. It looks like they areformed from the mud, gravel and the debris that flows into the pond. There is gravel inthis area as well. It looked like it would break if I touched it but it did not and it was ahard rock. It is very rough, has holes in it and I can see different kinds and sizes of rocksand small grains. This is a sedimentary rock. It fits the characteristics of a sedimentaryrock. It looks like it is composed of gravel, sand and silt. It is also a conglomerate. It is(Monroe, 2009)
  12. 12. ReferencesBlack-Necked Stilt and Mute Swan. Retrieved from on July 16,2011.Cattails. (2010). on July 17, 2011.Common Tule and Tidy Tips. Retrieved on July 16, 2011..Chavez, C. (2002). Self guided tour of shollenberger park. Retrieved on July 15, 2011..Ford, R. (1975). Geologic and hydrologic data. Retrieved from on July 20,1011Madrone Audubon Society. (2004). Retrieved from( on July 16, 2011.Monroe, J. and Wichander, R. (2009). The changing earth: exploring geology and evolution. Cengage pub.Mute Swan. Retrieved from on July 16, 2011.Origin and Early Evolution of Birds. (2007). Retrieved on July 16, 2011Petaluma. (2008) Photo retrieved from,_California on July16, 2011.Petaluma Visitors Center. (2009). Retrieved on July 14, 2011.Scollenberger Plants and Animals. (2009). Retrieved from www.petalumawetlands.orgon July 15, 2011.Tule and Tidy Tips. Retrieved on July 16, 2011Wetlands Campaign. (2009). Retrieved from July 14, 2011..