Curb Appeal

A wee bit of total dorkdom!

Time to dork out. As many of you know, I am rather partial to geology and am regularly noticing rock, or stone, in strange places: backdrops in movies, countertops at restaurants, walls in bathrooms, or roofs on old churches. But an even more mundane, and everyday, encounter with the geological world is through curbs. It’s a darned nifty easy thing to do; plus if you pay attention you can add a little history.

Here in Seattle there are generally three types of curb. Oldest are those made from granite quarried from Index. You see these 32 million-year-old, salt-and-pepper colored, igneous blocks, which extend down about eight inches below the ground, in areas such as Pioneer Square, Capitol Hill, Queen Anne, and First Hill. After the city stopped using these (I have no idea when), they turned to concrete with steel rails that protected the edge/corner of the curb. Finally, they abandoned the steel, I assume when stronger concrete was used. Ergo, you can impress your friends by pointing this out. I am sure their eyes will glaze over with delight.

Granite on the left, steel rail in the middle, modern concrete with ADA curb ramp

Impressed and excited by Seattle’s 32 million-year-old granite curbs but what about curbs made of stone from the same quarries used by Michelangelo? That’s what you can find in Carrara, Italy, the town below the area where the great sculptor obtained his lovely rock. The sidewalks are also marble. It began as a limestone formed in a quiet sea 200 million years, then about 27 million years ago a small tectonic plate rammed into, piled atop, and squeezed and baked the limestone, metamorphosing it into marble. As they say, Italians have way more style and class than many.

Gray Carrara marble curb and white Carrara marble sidewalk

But Michelangelo’s marble is still just a babe from a geological point of view. If you want to see really, really, really old curbs, and who doesn’t, then you have to go to Morton, Minnesota, home of another metamorphic rock. The Morton Gneiss (basically cooked and squished granite) is a 3.5 billion-year-old rock that looks a bit like a mixture of swirled bubble gum and licorice. For awhile it was the oldest known rock on Earth; geologists later found rock pushing 4 billion years old but it hasn’t been lucky enough to be turned to curbs so I won’t dwell on it. When the Morton formed Earth was so young that it didn’t even look like Earth: life consisted only of single-celled critters just emerging from the primordial ooze, so the planet lacked the lovely colors and plants and beasts that help give it its beauty.

Morton Gneiss curb in Morton, Minnesota

As you can imagine, I could go on far longer about curbs but will refrain. Wishing all of you a wonderful weekend. Be well. Be safe. Look down and admire the curbs.