Teacher's Guide
The San Francisco Bay


This lesson focuses on San Francisco Bay Estuary. Students will learn the importance of the bay.

Background Information:

The waters of the San Francisco Bay are a mixture of the salt water flowing in from the Pacific Ocean, and the fresh water rivers that feed into the bay. The water in the bay is neither salty or fresh, but brackish. This entire system is known as an estuary. The San Francisco estuarine system is made up of three bays: San Francisco Bay in the south and San Pablo and Suisun Bay in the north.

The San Francisco Estuary is a very dynamic system that constantly changes. The geology of the bay gives us clues that the system has changed through time. Mountain ranges surround the bay. The movement of the plates under California caused this series of hills and valleys. The bay, located in one of these valleys, was created about 2 million years ago. After the Pleistocene glaciers melted (15,000 to 18,000 years ago), this valley flooded. During this time, the Sacramento and San Joaquin Rivers must have flowed through the Golden Gate, eroding a very deep channel. The San Francisco to Oakland area was probable a flood plain with broad river beaches. In the stream valleys roamed now extinct species of camel, horse, bison, ground sloths, and saber tooth tigers. Fossils now found on Mt. Diablo, San Ramon area and Irvington, Fremont area are proof that these animals once lived in this area.

Salt Marshes

Salt marshes of the San Francisco Bay area are highly productive and extremely valuable to the bay's ecology. Salt marshes contain a variety of plants, but there are only a few common to all California salt marshes. Some of the most common plants found in the salt marshes include:
  • Salt bush - a low-lying shrub that can tolerate salty soils
  • Salt grass - long and narrow grass leaves, about a foot in height
  • Cordgrass - dies in the fall, but can tolerate many hours of submergence in the marsh water, filters salt out of its leaves where the salt crystals can be seen on its leaves
  • Pickleweed - stems that are pickle-like in appearance, absorb salt into their stems giving them a 'puffed-up' appearance, eventually these 'pickles' dry up and fall off

Animals of the Bay

A large variety of animals live in the San Francisco estuarine system. Mammals, birds, reptiles, amphibians, invertebrates, protozoa, and fish all occupy a place in this system. The system has many parts because of the need for larger animals to feed on the smaller animals. This food chain gives us clues of why animals eat and live where they do. Many organisms depend on the bay for food, safety, and shelter.

Student Activity:

  1. Print out a copy of the San Francisco Estuary map choose either html version or pdf version for each student.
  2. You may also wish to make an overhead copy of this map, or bring the map up for the students to see using a computer presentation system.
  3. Introduce the students to the San Francisco Estuary system using the background information provided.
  4. Point out the three different bays within the system.
  5. Locate the main bridges of the bay. (Oakland-San Francisco Bay Bridge, Golden Gate Bridge, San Rafael-Richmond Bridge, San Mateo Bridge, Dumbarton Bridge, Carquinez Bridge, Benicia Bridge)
  6. Find the city of Fremont on the map. Ask the students to color Fremont.
  7. Identify which bay Fremont's waters flow into. (San Francisco Bay) and which bridge is nearest Fremont.
  8. Inform the students that the salt marshes are located in the lower end of the San Francisco Bay, all along the inside of the bay where Fremont is located. Coyote Hills is one such protected area of salt marshes. Ask students if they have ever been to Coyote Hills and seen the salt marches.
  9. Save this map for future reference.
4-6 Watershed Curriculum Next Lesson