An excerpt:

January 5, 2015

The tideline is one of the richest biological regions on earth. It is also a fluctuating, fractal line that rises and falls each day and over thousands of years. Today, as the sea is receding, we will walk along the tideline to the westernmost point, a series of rocks called the Boneyard. Along the way we will stop at 7 stations to consider the intersection of tideline and timeline and forms of sense, presence, and absence in this particular landscape.

A 1972 photograph of this shoreline shows only this building, the Ocean Shore Canning Company, and 7 houses occupying this area, the rest being open meadow. Before that, this site was a farm owned by a Japanese family until World War II, one of many Coastside families who lost their homes to the internment laws. For several thousand years before that, until the Spanish missionaries arrived in 1769, around 50 Chiguan Ohlone people lived here in a settlement called Ssatumnumo. They were nomadic people, going up to the hills for the acorn harvest and coming down the sea for the salmon run, but this salt marsh and the shelter of this headland, was home base, and one of the richest, unexcavated archaeological sites in California lies with a few hundred yards of here.

Today’s low tide, which is at 4:19, is one of the lowest of 2015, and the lowest this year that coincides with a full moon. These spring tides – so called because they spring up – nearly all take place in the winter months, due to the alignment of sun and moon and earth, a celestial pattern called a syzygy. In turn the lowest ebb generates the highest flow, and in 6 ½ hours the tideline will be about 6 ½ feet higher than it is right now.

A chart of sea levels over the past million years looks like a graph of breathing, a predictable rise and fall during which the water withdraws 400 feet below its present level as the climate cools and ice builds at the poles, and then rises to our current level as the ice melts. This has taken place every 100,000 years, an EKG of the planet. However, the rise happens quickly, over just 20,000 years, while the cooling period is much slower, because ice melts more easily than it forms. On the timeline of ice ages, we are living in the pause that occurs between the last rapid melting and the next slow cooling phase. We call this the Holocene Epoch, and it has coincided with the emergence of all human societies, though whether this is coincidental is a matter of debate.