Book Readings: Week 4

For my Marine Resources class (GEOG 646) at SF State this semester I am reading The Sea Around Us, by Rachel Carson (1951), and The Tide: The Science and Stories Behind the Greatest Force on Earth, by Hugh Aldersey-Williams (2016). Please check out my first Book Reading blog post to read about why I chose these two books and why I chose to blog about them concurrently.

This week in The Tides, Aldersey-Williams recounts the history of Scandinavian invasions of the English coast, such as the Battle of Maldon and the Battle of Fulford. I found it interesting how much the tide influenced the success of these invasions, and how even though the English coast was subjected to a much greater tidal range than the coastlines of Norway and Denmark, the greater seamanship of the Vikings helped them overcome any advantage that local knowledge of the tides might have conferred on the English.

The author then talks about Bede, an incredibly intelligent 9th-century Benedictine monk who investigated many natural phenomena with a scientific approach, including the concept of time. It's through his investigations into time and his attempts to find a consistent method for determining the date of Easter celebrations that he came to study the tides. He noted that the lunar Jewish calendar and solar Roman calendar would sync up every nineteen years, in accordance with one of the slowest measurable tidal rhythms. A century later, Abu Ma'shar al-Balkhi recognized the association of the angle of the moon above the horizon with the tides.

I was particularly interested to hear Aldersey-Williams return to the present day and talk about an art installation at a beach in Liverpool, England. This installation consists of bronze statues of men on the beach that get submerged to varying degrees with each high tide. What interested me about this art installation was that such an art piece would never fly in most of California. Perhaps it would be more likely for such an art piece to exist in Venice Beach or Redondo Beach, where the coast is more urbanized and highly trafficked, but for most of the California coast the idea of installing something man-made in the intertidal zone of a beach, especially something that alters the view of the coast in such a significant way seems unlikely and not in keeping with the culture of coastal preservation that we tend to have here in the Bay Area. In fact, local Liverpudlians pushed to have the art installation stay in place when attempts were made by the local council to remove it due to safety concerns, and I'm pretty confident that wouldn't have happened here in California!

Aldersey-Williams then gets into the concept of fractal geometry, and how the more closely you observe something the more complex it seems. He brings this up in relation to the fact that how long a coastline is depends on how closely you observe it: Do you follow every minute nook and cranny and curve and kink in the coastline, or do you draw a more generalized boundary? And how do you define the coast? Do you use the low tide line? Or mean high water? Are you keeping in mind that the coastline at a low tide is not necessarily longer than a coastline at high tide if the coastline at low tide is less "kinked"? (Similar concerns around definition affect how we quantify the size of the intertidal zone due to tidal range, slope, etc.)

I appreciated this discussion in the book because we have had similar discussions in my Marine Resources class on how one defines a coast. I also was tickled by how this discussion highlighted how interdisciplinary the study of the tides can be, encompassing history and geometry as well as physics, geology, and other "hard" sciences.

Aldersey-Williams then moves on to Morecambe Bay, the largest intertidal area in Britain. Five rivers flow into it, and there are lots of exposed mudflats, seaweed, eelgrass, birds, and more. Even though it's not feasible at all, it is technically legal to drive across the exposed sands at low tide. Again, I thought about how this would never happen in California. Besides the huge safety risk this would pose, driving through sensitive intertidal areas seems against everything we are taught about the ocean and the coast.

In reality, a huge amount of water flows in and out of the flats of Morecambe Bay. These flows are so powerful that they alter the sands drastically, so much so that a survey map of the flats that is only a few years old will be outdated due to major channels being altered. This means the flats are also dangerous to traverse, but because the flats are home to a vast expanse of lucrative and tasty cockles that are harvestable at low tide, many people venture out onto the flats recklessly. Aldersey-Williams recounts multiple tragic tales of people caught out on the flats who died when they got lost or stuck in the sands and drowned the tides came in. The author makes the point that greater literacy and respect for the tides would be beneficial to public safety.

Aldersey-Williams repeatedly talks about how tides inspired religious scholars, from Bede to Robert Grosseteste. inspired by the religious significance of light, these scholars made the connection between the light of the moon and the tides. Thomas Aquinas was the first scholar to conceptualize the tides as a force, although he did so in order to prop up the idea of the existence of a god (who created the force of the tides) and to discourage the notion of the tides as a knowable, natural phenomenon which didn't need a divine explanation. Finally, the author talks about how the tides could have even played a role in Christian mythology. He says that the most plausible modern explanation for the story of Moses parting the Red Sea is that Moses was likely a person with a good understanding of local tides. Although tides in the Red Sea are generally semidiurnal, local wave effects in the Red Sea basin make for diurnal tides at certain parts of the Red Sea coastline. Aldersey-Williams argues that a wind-influenced, extremely low tide would have exposed quite a bit of land to allow for passage at the north end of the Red Sea, and that a diurnal tidal cycle would have allowed for that low tide to last throughout the whole of an entire night. The author admits that this is all speculation, but it's interesting to think about what role natural phenomena like tides could have played in various legends and myths.

In The Sea Around Us this week, Carson talks about the accumulation of sediment in the ocean, from inorganic sources such as erosion of coastal rock, but also from the descent through the water column of the siliceous and calcareous shells of dead phytoplankton. I like that Carson makes the connection between this accumulation of sediment with the vast layers of sedimentary rock we often see on land, indicating that an ocean used to exist where those rock layers are present. It's interesting to note how new the technology used to obtain sediment cores was when the book was published. The ability to take core samples 70 feet in length only became possible a few years before the original publication of Carson's book.

Carson then moves on to the formation of islands. She moves from one less-traveled island to the next in the oceans and in the Mediterranean (such as Ascension Island in the Atlantic, and Bogoslof Island near Alaska), discussing their formation and sometimes disintegration. I've always had an attraction to islands and island ecosystems and reading Carson's descriptions of these places made me want to travel and see them for myself.

Carson also discusses how these remote islands, products of volcanic activity, were colonized by fauna and flora. I was impressed to learn that living insects and spiders had been captured nearly three miles above the earth's surface, and that scientists were able to obtain such small creatures at such heights before Carson first published her book. Before such discoveries, Charles Darwin showed that he was able to raise various species of plants from a ball of mud lodged in the feathers of a seabird that was able to traverse large distances across the ocean. This ball of mud must have contained the seeds of plants Darwin ended up being able to grow.

I've been saying this every week, but as usual I was entranced by Carson's descriptive writing. I loved her comparison of falling sediment in the oceans to snowstorms and blizzards in the sky, and of accumulated sediment layers to snowdrifts. I also loved reading about what the ocean is like at the surface when there is an underwater volcanic eruption, and Carson's description of the explosion that destroyed Krakatoa in 1883 was captivating. I was shocked to learn that the explosion was heard thousands of miles away in Madagascar, and that the volcanic ash hung in the skies around the globe for at least a year after the explosion, making sunsets around the world a vibrant pinkish-red during that entire time.

Carson's descriptions of island ecosystems and of island flora and fauna are also enthralling. When she discusses the delicacy and uniqueness of such ecosystems and how humans have repeatedly ruined island after island and caused mass extinctions by either resource extraction or the importation of non-native flora and fauna, the anger and passion in her writing is almost palpable, despite her restrained and professional tone. It is easy to see how she came to write Silent Spring a little over a decade after first publishing The Sea Around Us, and as an aspiring environmentalist I find it gratifying to read the words of someone writing in 1951 and see phrases like "nature's balance" and "pattern of life" because it drives home the fact that these are not new concepts in biology and ecology, but foundational and well-established ones.

Carson then moves on to talk about ancient seas, and how over the course of geologic time the sea has risen to cover much of all the continents, then retreated hundreds of feet as water became captured in glaciers during ice ages, and then risen again as glaciers melted. It was good to be reminded of the sea's dynamic nature and how humankind in ancient times experienced very different oceans and coastlines than we do. I also appreciated the point that it would be good to use technology to explore under coastal waters to look for former human coastal settlements that would have been active and thriving when sea levels were much lower. I also liked reading about the fact that even in the most inland places, like at the top of a mountain range, evidence of former oceans can be found as sedimentary layers of rock. It drove home the point that no matter where one is on Earth, one can always find the presence of a sea, although it may be an ancient one.

I'll be blogging again about both books at the same time next week. Stay tuned!

References:

• Aldersey-Williams, H. (2016). The tide: The science and stories behind the greatest force on Earth. New York, NY: W. W. Norton & Company, Inc.
• Carson, R. L. (1951). The sea around us (1989 ed.). New York, NY: Oxford University Press, Inc.