LANDFORMS

A Geomorphologist's Dream

The wind, ocean and tectonics have greatly contributed to the numerous landforms found on the Peninsula. The list below includes some of the more classic landform examples (Evens, 1993), and emphasizes the uniqueness of the Point Reyes Peninsula. Can you find these landforms on the map above?

1. Bolinas Lagoon is a classic example of a bay mouth bar landform that acts as a barrier between the lagoon and the Pacific Ocean.

2. The process of concretion is illustrated by the Bolinas cliffs and Drake's Beach.

3. Drake's Estero and Bolinas Lagoon are examples of a drowned river valley and were created by the rising ocean levels inundating the valleys with sea water.

4. The effects created by geologic faults are visible at the north end of Kehoe Beach, Drake's Beach and Point Reyes Headlands.

5. Tomales Bay and Olema Valley are examples of fault-controlled valleys.

5. The San Andreas fault line cuts through and has greatly contributed to the formation of Tomales Bay, Olema Valley and Bolinas Bay.

6. Examples of saltwater and brackish lagoons and estuaries are visible at Abbott's Lagoon, Bolinas Lagoon, Drake's Lagoon and Limantour Estero.

7. Landslides are apparent through-out the Peninsula, in particular, along the coastline between Wildcat Beach and Palomarin, Seven Lakes at Lake Ranch, and the southwest end of Drake's Beach.

8. A marine-built terrace can be observed extending from Bolinas Mesa to Limantour Estero.

9. Marshlands on the Peninsula are not widespread but do support a diversity of plant and animal life. Freshwater marshes found on the Peninsula include Ledum Swamp, upper Olema Marsh, Laguna Ranch Marsh, Kehoe Marsh and upper Abbott's Lagoon; brackish marshes consist of lower Olema Marsh and Pine Gulch Creek; and salt marshes on the Peninsula are found at the south end of Tomales Bay, along the edges of Bolinas Lagoon, and at Drake's and Limantour Estero.

10. Olema Creek is the only example of an offset stream found on the Peninsula.

11. An example of a sag pond is well represented by Olema Valley on the eastern side of highway 1.

12. Sandspits on the Peninsula include Stinson Beach and Limantour Spit.

13. Arch Rock, between Sculptured Beach and Wildcat Beach, is the only sea arch found along the Point Reyes seashore.

14. There are numerous inaccessible sea caves below the Point Reyes Headlands near the tide line.

15. At Tomales Point, Point Reyes Headlands, and Double Point you will find perfect examples of a sea cliff.

16. There are several examples of sea stacks at Double Point, Miller's Point, Chimney Rock, Elephant Rocks and Bird Rock.

17. At Dillon Beach, Elephant Rock is an excellent example of a tafone (a honeycombed weathering pattern caused by wind or rain).

18. Duxbury Reef is "the largest shale reef in North America" (Evens 1993, pg. 40) and representative of an underwater reef.

19. A waterfall beach can be seen at Alamere Falls near Double Point at the southern end of the Peninsula.