An edge can be a linear boundary, but it is foremost an area of exceptions. At edges, there are events that are unlikely to happen in the center of systems. These exceptional events can sometimes tell us about the systems, about what they really are in relation to other systems. This is one reason why coastlines are interesting: they are where Earth’s largest systems—lithosphere, hydrosphere, and atmosphere—interface all together. Even an extraterritorial system intervenes into this confluence: “A wave is the interface of ocean, land, air and sunlight.”1

In 1960, Trieste, a U.S. Navy deep-diving research submersible, reached the ocean floor in the Challenger Deep, the deepest part of the Mariana Trench.2This was the first time a vessel had reached the deepest known point of the Earth’s oceans, measured to be between 10,911 meters (35,797 ft) and 10,994 meters (36,070 ft) deep.3

The ocean, which composes 97% of Earth’s hydrosphere, is the least explored area on the planet. Oceanographers state that only 5% of the ocean has been explored, and the history of deep sea exploration is charged with military motivation and economic whims. Though all living organisms have their origins in the ocean, the vast majority of its territory is a dangerous and foreign environment to the human anatomy.

Without technological aid, human beings mostly experience the ocean at beaches. They are the dominant impression of the ocean. What happens at the beach is, however, from the perspective of the ocean, very exceptional and rare. Deep water currents make up 90% of the ocean currents. These are governed by the interaction between water temperature and density; nearly pure hydrology. Surface currents make up the remaining 10%, and are governed by wind, sun and moon, which are part of the atmospheric and extraterrestrial systems. The surging, breaking and reflecting of waves and tides happen at the edges of the surface currents, where all three major earth systems and extraterritorial influences meet. The familiar upsurge and backsplash of waves are exceptions and externalities to the systems, involving never-ending collisions, conflicts, and resolutions between hydrosphere, lithosphere, atmosphere, and extraterritorial(-estrial) systems.

Coastlines are an intersphere of the Earth, a confluence of edges that at the intersection every major system. They are perhaps the most dynamic example of the exceptional nature of edges: permeable territories that elude any single territorial identification, serving as a passage to connected systems that may go unnoticed or seem unreachable.

  1. “Interfaces,” Scripps Institution of Oceanography, UC San Diego. Interfaces. 22 September 2019. https://scripps.ucsd.edu/research/themes/interfaces.
  2. “Trieste 1 (Bathyscaph),” Naval History and Heritage Command. 30 September 2015, https://www.history.navy.mil/content/history/nhhc/research/histories/ship-histories/danfs/t/trieste.html
  3. Amos, Jonathan. “Oceans’ deepest depth re-measured,” BBC News, 7 December 2011, https://www.bbc.com/news/science-environment-15845550.