Geology of Sailing

To the sailor, rock science may seem arbitrary.  On the water, a view of the geologic horizon is nothing more than that, a view – at least seemingly so.  So then, what is this article all about?  I could argue on many fronts: for example; a) that a better understanding of the Earth’s crust would have prevented some of the near-death experiences Captain Cook lead his crew on while exploring Terra Australis Incognita.  B) Viewing towering mountains from sea could predict fish populations. Or, c) as your fiberglass recreational vessel drifts closer and closer to the sound of breakers and you stare at greywacke cliffs, you may appreciate having learned a bit about the study of the Earth’s physical structure. And though I would argue these things, I will not here.  Here I will lay out the facts: 1) geology directly influences climate; 2) exposed geology predicts submerged geology; 3) coastlines are fucking beautiful.  And with that, please read on my furry mariner friends.

We are in an ice age.  Before you get your panties in a bundle let’s define the terms – an ice age is defined as any period on the Earth that continental size glaciation is present.  Think for a second…. Yes, there are two continental size glaciers on our planet: Antarctica and Greenland. What you may have been thinking of, with the word “ice-age” is glacial period. A “glacial-period” is any point when the Earth’s surface is mostly covered in ice – that is more than 50%.  Glacial periods can be predicted and happen roughly every 10,000 years. The Earth has only seen a few ice ages since its creation 4.6 billion years ago. We can all imagine why an ice age alters climate.  With average temperatures at about roughly what we experience today – oceans, continents, poles and alpine regions all have their own unique climates – including temperatures and weather patterns. During Green Ages, that period opposite of an ice age, temperatures are warmer, the poles are melted and glaciers, both alpine and continental are gone. Glacial Periods, during ice ages, are fucking cold. Things are frozen. No one is navigating across any ocean. How are ice ages and green ages influenced by geology?  Tectonic drift, is the answer.  We know that continents drift. They also are formed, created, and subducted back into the Earth’s mantle.   As a continent drifts past a pole, ice begins building on the land mass, forming giant continental size glaciers.  We know that at least 5 continents have drifted over the poles, and thus we have had roughly five ice ages. Glacial periods are a little harder to write about, as there are more arguments over the matter. Though we know that they occur at the same time a known wobble in the Earth’s orbit exist.  The wobble and the glacial period happen roughly for 10,000 years every 10,000 years. To dig into things a bit deeper (there was a pun there), rocks hold temperatures longer than water.  This is why Antarctica is always frozen and the artic melts during the summer. As more land is exposed to the sun’s rays, the temperature of the Earth will rise. The feature of physics happens regardless of the movement of continents – it is a feature of rock.  Remove the ice and the rock beneath heats.  Hotter crust means hotter atmosphere.  Hotter atmosphere means warmer oceans.  Warmer oceans lead to bigger storms – think Caribbean during late summer! Sailor be warned – learn your geology, if not for yourself, for your messmates!

The Peruvian Coast has some of the mightiest mountains on the globe. Rising over 20,000 feet from sea level! Likewise, the Peruvian Trench, which stretches the exact distance of the Andes, has depths up to 26,000 feet – that’s over 4 thousand fathoms – unfathomable! This means you can float on your little dingy in one of the world’s deepest ocean trenches and look up at some of the world’s highest mountains!  This is not by accident. It is not by some bold blow from Zeus.  It is a feature of geology!  As two plates collide, in this case the Nazca Plate (the Pacific Side) and the South American Plate, one of them is forced down and is subducted under the other.  Peru is the country which is riding on the Western edge of the South American Plate.  It is riding over the Nazca Plate.  This forces the South American plate up – The Andes, and the Nazca Plate down – The Peruvian Trench.  This geological event is duplicated all over the globe.  This process of subduction is building trenches and mountains on most coastlines.  This same process creates volcanic activity, and often if there is a line of volcanoes (exceptions exist because of “hot spots”) there is an underwater trench (Japan, Aleutians, Cascades).  Volcanoes exist because of the pressure created during the subduction process. The subducted crust becomes so pressurized in boils and sends its contents bubbling up through the surface in the shape of volcanoes. Trenches also exist in open water – such as the mid-Atlantic ridge.  This ridge line has a feature in the middle which is a trench.  At a depth of 25,000 feet this ridgeline is the result of two tectonic plates moving away from each other.  As the plates creep away, a decrease in pressure leads to the production of magma and eventual the spewing of lava at the ocean’s depth. This divergent process at the Mid-Atlantic ridge has been happening for 2 million years and is responsible for the separation of the Americas from Africa – Pangaea. The plates under the ocean have been formed through this divergent process, and they are mostly basalt.  The counterpart to basalt in granodiorite – which composes most of the Earth’s continental plates. Most people buy granodiorite countertops – not the more expensive granite countertops – which is only a difference in K – potassium – which is slightly pink. Basalt is denser than granodiorite, though this feature is hard to wrap the mind around because granodiorite is much harder.  Granodiorite is formed by hardening magma, and thus is formed over a very long amount of time, which allows individual crystals to fully develop. Basalt, in contrast, is formed by lava, and hardens very quickly, leaving air pockets (vesicles) and no visible crystallization.  Because basalt is denser, it always sinks beneath the less dense granodiorite – which is why continents “float” on the surface – which is why we have very dynamic terrain which allows for pooling water – we call oceans! The oceanic crust (basalt) sits lower than the continental crust – this would be true even without water on our surface.

My mother was into lighthouses.  As a child I climbed the stairs of many lighthouses on the East Coast – or at least I sat in the parking lot whining about not wanting to climb the lighthouse stairs.  On the East Coast lighthouses are extremely tall. Cape Hatteras Light is 207’ tall. In fact, the tallest 30 of all the light houses in the United States are on the East Coast – with the exception of a 138’ lighthouse in Hawaii. This feature of coastlines is geologic.  The coastline on the West Coast is higher due to cliffs, yes, which means the light can be closer to the ground, though also the water is shallower on the East Coast, which means the light needs to be higher, to warn ships sooner!  The geology of the East Coast is gentle sloping sand.  The gentle slope creates shoals and bars well out into the ocean.  Lighthouses on shore must be way up to send their light as far as possible out over the horizon.  On the West Coast, due to the trenches which mirror the steep cliff coasts, vessels can sail much closer to the shore, which means lights need not be so high. These differing coastlines also allow a traveler to determine where he’s at. A 16^th century ship could tell the inlet to the Chesapeake by the dunes and trees.  Whaling ships in the 19^th century could determine whale depots and outpost based on distant cliffs. As we navigate the ocean seas for weeks and months on end, it is the sight of land, brought on by rock and botany, that excites us most. City lights, dwellings and man-made towers are convenient, but not nostalgic to the seaman. Rip up the loran stations as they block the clean view of the mountains!

It is not solely in these three illustrative points that land and geology are relevant to the sailor. Understanding river flow and sand movement can lead to a great deal of practical utility. The meteorologist may use mountain and hills as barriers to wind flow.  Great ocean currents swelling up trenches and turning up beach wrack and wind can summon fog.  Coral needs rock and trench. Fish need sediment. Voyagers need flowing streams. ATON units need pleasant back drops to install their equipment.  It is rock that contrasts water!  The sailor needs rock, to have his water so alive!   And with this rant and science, I bid you farewell. The conclusion I’ll leave you with is back to my original argument.  That without science – any science is all science – we will continue to deny safety and dogma-free poetry to the mariner! The sailor is doomed to be a philosopher, has he any time on his watch to star gaze, and that philosopher needs science to be sound, to be fathomable.   To leave you with a note of my citations: I have none.  I studied geology under a man named David – Professor David M______.  David’s claim to fame was the discovery of a fifth rock-family the granite-pipe. I remember this man getting naked after class field trips to local beaches, where we studied geological horizons.  While I don’t remember his cock specifically, I remember the terrified faces of my peers – which was enough for me to like this professor.  I digress…. David was one of my favorite teachers. His love of rocks couldn’t have outweighed his passion for science, as it was to present in his every demeaner.  He slammed modern culture, and he dissed laziness, conformity, and the safe-place movement, all in the name of method, evidence, theory, and trial.  David’s joke, which is going to become a sailor joke if I have anything to say about it is: that the Greek word for rock is “petra.” The Greek word for child is “paedo.”  Seeing as how we English speakers love to corrupt language, we insisted to change paedo, to peda, because it is phonetically easier to pronounce.  And then naturally pedaphile became the lover of children – or a child molester.  The joke was that David’s geology team (think debate team for rock lovers) decided to use the proper Greek term for rock and the Greek term of love, in an all out bash of 21^st century English etymology.  They call their rock team the San Francisco Petraphiles.  Yes David, I am a petraphile too, even more so after taking your class.