Alamere Falls, Point Reyes National Seashore

Alamere Falls, Point Reyes National Seashore

by | Jun 22, 2022

Alamere Falls is located about 0.4 miles (0.6 km) north of Double Point where Alamere Creek cascades 40 feet (12 m) over a sea cliff, directly into the ocean at high tides and otherwise onto Wildcat Beach in the Phillip Burton Wilderness of Point Reyes National Seashore, about 6 miles (10 km) south of Olema and 6.4 miles (10.3 km) northwest of Bolinas, California. Upstream of the main Alamere Falls is upper Alamere Falls, consisting of three separate cascades all fed by Alamere Creek, that in combination drop approximately 20 to 30 feet (6–9 m). Alamere Creek starts at an elevation of about 1,200 feet (365 m) on the south flank of Firtop Hill and flows generally southwest for about 3 miles (5 km) draining a watershed of about 1,730 acres (700 ha). Alamere Falls is a rare example of a suspended creek channel that occurs where waves erode the seacliff at a faster rate than the creek erodes the channel bed. Other examples include McWay Falls on the Big Sur coast, in Oregon at Hug Point Falls near Arch Cape, and Blumenthal Falls at Cape Falcon. The Point Reyes area consists of two contrasting geologic provinces separated by the San Andreas fault that is roughly aligned with the Olema Valley. East of the San Andreas fault, the Coast Ranges consist mainly of rocks in the Franciscan Complex, which is a belt of highly deformed and variably metamorphosed greywacke, mudstone, volcanics, limestone, and chert. The Franciscan Complex is generally accepted to be an accretionary wedge formed above a subduction zone when the western edge of the North American plate was mainly a convergent boundary from the Late Jurassic to the Miocene. In contrast, the area west of the San Andreas, has a Cretaceous granitic basement similar to the Sierra Nevada Mountains. The granitic rocks are overlain by a thin layer of early Eocene strata followed by a thick sequence of Miocene sedimentary rocks. These rocks are exposed at the Alamere sea cliffs as a formation called Santa Cruz mudstone with a high silica content resulting from the deposition of a diatom called Nitzchia reinholdii in the late Miocene age.

The historical inhabitants of the Point Reyes area at the time of European arrival were the Tamal Coast Miwok who had lived in the area for thousands of years. The Coast Miwok subsisted as seasonal hunters with a diet consisting of fish, clams, mussels, and crab, in addition to the deer, elk, bear, mud hen, geese, and small game they hunted with spears and bows. They also gathered a variety of plants for both immediate consumption and for storage in granaries. The land of the Coast Miwok remained undiscovered by European explorers until Captain Francis Drake first sighted and mapped the fog-shrouded headlands in 1579 from the Golden Hind, which was ladened with gold and treasurers such as porcelain taken from Spanish galleons traveling between Manila in the Philippines to Acapulco in New Spain. Drake claimed the land for Queen Elizabeth I and named it New Albion before setting sail southwest to complete his circumnavigation of the globe before returning to England in 1580. Point Reyes was officially documented on Spanish maps in 1603 when Sebastián Vizcaíno sighted the headlands on the Roman Catholic feast day of the three wise men and named the point ‘la Punta de Los Reyes’ or the ‘Point of the Kings’. The Coast Miwok continued their habitation of the area until late in the 18th century when the Spanish built Mission San Rafael and Franciscan padres journeyed to Point Reyes to convince them to move to the mission where they were converted and forced into labor. In 1821, the Mexican War of Independence ended and the Spanish mission lands were broken up into private land grants after the Mexican secularization act of 1833Rancho Las Baulines was a Mexican land grant of 8,911 acres (3,606 ha) given in 1846 by Governor Pío Pico to Gregorio Briones. The grant extended from Bolinas Lagoon north to the southern end of Drakes Bay and Wildcat Beach and inland to the Olema Valley.

Point Reyes National Seashore is 71,028 acres (28,744 ha) of parklands established in 1962 that allow historical agricultural uses to continue and is maintained by the U.S. National Park Service as a nature preserve. Nearly half of the National Seashore is within the Phillip Burton Wilderness which established 33,373 acres (13,505 ha) of forested ridges, coastal grasslands, sand dunes, and rugged shoreline to protect one of the most diverse landscapes on the California coast. The wilderness area is named after Congressman Phillip Burton who served in the U.S. House of Representatives from 1964 until his death on April 10, 1983. The dramatic rocky shores of the National Seashore result from the dynamic marine and terrestrial processes that shape the landscape, resulting in a geomorphic setting where steep sea cliffs are punctuated by coastal draining rivers and streams. River channel incision erodes the landscape vertically, and waves erode the landscape horizontally, a process that can form cliffs especially when the adjacent landscape is steep. When river channel erosion outpaces sea cliff formation, the river channel will be incised to sea level through an otherwise raised sea cliff edge. Incision-dominated channels might occur when drainage basin areas are large and river discharge is perennial, or when sea cliff retreat is slowed due to low wave energy or the geology is particularly resistant to wave erosion. When sea cliff formation outpaces channel incision, the cliff is maintained and channels do not cut through the cliff edge to sea level. These channels end abruptly as suspended or hanging valleys called coastal knickpoints. These occur when cliff retreat is rapid due to the duration of wave attack on the toe of the sea cliff in combination with low available stream discharge. Ephemeral streams where water flows to the beach only during rainy periods are common in California and a good example is Alamere Falls where the creek often has very low flow presumably because the drainage basin area is small and precipitation is seasonal, and the toe of the mudstone sea cliff is easily eroded by ocean waves at every high tide. Read more here and here. Explore more of Alamere Falls and Point Reyes National Seashore here:

About the background graphic

This ‘warming stripe’ graphic is a visual representation of the change in global temperature from 1850 (top) to 2022 (bottom). Each stripe represents the average global temperature for one year. The average temperature from 1971-2000 is set as the boundary between blue and red. The color scale goes from -0.7°C to +0.7°C. The data are from the UK Met Office HadCRUT4.6 dataset. 

Credit: Professor Ed Hawkins (University of Reading). Click here for more information about the #warmingstripes.

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