Erratic Behavior

When I moved east to Boston many years ago, Plymouth Rock was about the sum total of my knowledge of New England geology. Basically, I knew nothing but a name. It turns out though that the Pilgrim’s infamous landing point was one of my favorite geologic features, a glacial erratic. If you are not familiar with this flotsam of the Ice Age, you are missing out. Erratics are rocks—technically, any size but often noticed because they can be as big as the proverbial school bus—carried by glaciers and abandoned when the ice melted and retreated. Left behind by the ice, Plymouth Rock was in the perfect position to provide a stepping stone for the new arrivals, assuming you buy that story of the Mayflower migrants, which many do not.

Although New England geology is relatively dull compared to Seattle’s active tectonics (i.e. earthquakes and volcanoes), it shares a common feature with my fair city. Erratics—a dozen plus—dot our landscape.

My map of some of Seattle’s Erratics. Here’s a link to it.

Our most famous is the Wedgwood Erratic, aka the Wedgwood Rock, Lone Rock, or Big Rock. According to the wonderful local historian Valarie Bunn, it was famous as early as July 4, 1881, when 16-year-old Martin Weedin scrambled to the top of the 19 foot tall rock and “read the Declaration of Independence in a very creditable manner.” (Seattle P-I, July 6, 1881) The Big Rock continued to attract peak baggers and eventually became a mecca for The Mountaineers, which used it as a classroom. Geologists have determined that the rock rode the ice highway from Fidalgo Island near Anacortes, about 75 miles north.

Erratic Mountaineers climbing, Lloyd Anderson Collection in The Mountaineers, courtesy of Lowell Skoog, Archivist. The rock is 75 feet long.

Another outstanding erratic, that is outstanding in a field, is one “recently” discovered in Leschi Park (early 2000s). What makes this one special is that it is chock full of fossils, in particular, clams in the genus Buchia. Since its unveiling (it was found by people clearing the vegetation around it), geologists have debated whether the rock came from near Mt. Baker or southern BC. They tend to agree that the clams lived about 150 million years old and are from what is known as the Nooksack Group of rocks.

Intriguingly, those clams have traveled before; the Nooksack Group is part of an accreted terrane, or rocks sutured on to North America by plate tectonic movement. What geologists can’t agree on is where the Nooksack rocks originated. Did the tectonic highway carry them from Baja California or someplace else to the west? Either way the erratic’s travels are minimal in comparison to the travels of its parent material.

Not that everyone cottoned on to our erratics. At least two, long known and seemingly valued as landmarks, no longer exist: at 48th Ave. S. and S. Ferdinand St. and Broadway Ave. and Madison Street. Both were locally called Big Rock (seems to me that people could have been more creative with their names, such as The Madison Marvel, The Whopping Boulder of Ginormity, or Ferdinand’s Glory Stone, and served as meeting places, and apparently, a bit more. In an 1892 article in the Seattle P-I, an unnamed reporter wrote that the Big Rock on Madison was scheduled to be blown up, noting that in the past “when habitations in that part of the city were few and scattered lovers made it their trysting place…fortunately for the lovers who have whispered their confidence under its shadow, the big rock tells no tales.” I haven’t been able to figure out when either was destroyed.

Although we Seattleites ultimately saw our erratics as impediments, not everyone was so dismissive. Germany’s greatest writer and philosopher, Johann Wolfgang von Goethe, was a passionate geo-geek, particularly regarding what he called Granitgeschiebe, or granite that is shoved. His interest in die Wanderung der Granitblöcke (the wandering of granite blocks) began in the 1780s, when he encountered them in Germany, and blossomed in the 1820s, when he wrote about them in Wilhelm Meister’s Years of Wandering.

Goethe initially thought that giant floating rafts of ice had carried the erratics, or foundlings (Fündling) as some called them, but later concluded that sheets of ice were the primary mover. Based on this idea of an icy conveyor belt, Goethe proposed an even more radical notion, that Europe had experienced an “epoch of great cold,” or what was soon called the Ice Age. As I noted two newsletters ago, Louis Agassiz is generally credited with popularizing the idea of the Ice Age but he acknowledged that Goethe “alone unified all the indications into a definite theory."

The 700 tons foundling known as Markgrafenstein that inspired Goethe - From Wikipedia

Goethe is famous for his many life maxims. One of my favorite is: “In nature we never see anything isolated, but everything in connection with something else which is before it, beside it, under it, and over it.” Certainly sounds to me like he describing erratics. Rock on Goethe!