587. The Alpine Zone & The Idaho Batholith

The Alpine Zone

If you haven’t been to the Alpine Zone yourself, you’ve seen pictures, you’ve been to movies… you know what it’s like. Roughly defined the Alpine Zone is anything above tree line where conifers and deciduous trees can’t survive. Rock, dirt, earth is exposed at higher elevation but it doesn’t mean that there isn’t a thriving environment. Plants grow there, in the form of algae, lichen, flowers. Animals live there, raptors, mountain goats, marmots, chipmunks, and sometimes people.

I’m not sure how that turned out above, but it’s a fascinating map showing all of Idaho’s unique ecozones and regions. Each broken out based on individual geological localities bound together by common characteristics unique to that zone. And one of those larger regions is called the Idaho Batholith.

The Idaho Batholith

What got me interested in this topic was a recent hike to Phi Kappa Mountain in the Pioneer Mountains of Idaho. Greta Sallings and her mountain pup Gretchen accompanied the two Golden’s, Kyra & Koufax… and I was there too of course also, as well. On a subsidiary point of Phi Kappa around 10k feet, above tree line, in the Alpine Zone, we came upon this interesting rock formations…

Shale Schist or Slate Schist

These rock formations, as best as I can tell, are either called Shale Schist or Slate Schist. Through a Google Image search, there are similar formations in the Alpine Zone across the world. It’s a combo rock formed from sedimentary and metamorphosis. The sedimentary silt gets compacted by pressure and heat (metamorphosis)… and thus you get these awesome piles of geometrically aligned thin sharp rock called Shale Schist. Here’s a few things I could come up with to explain it (The Bubbly Professor and Sciencing):

As a truly committed student of wine, you probably know that shale is a type of soft, foliated sedimentary rock composed (at least in part) of clay minerals and (sometimes) volcanic ash. Shale has visible stratification and a tendency to break or split along “layers” (known as “planes of weakness” or “rock cleavage” in geo-speak). This tendency to split along planes is known as fissility (which is just such a fun word).

The Bubbly Professor

Shale is fascinating on its own but there’s more to the story, as shale can be transformed into slate, schist, or gneiss. These three types of rock are produced via varying degrees of metamorphism—changes resulting from heat, pressure, and deformation—and they all have different appearances and characteristics. Some of these differences are discussed below:

Slate: Slate, formed from shale, is a finely grained rock that may be formed under relatively low temperature and pressure conditions (low-grade metamorphism). Slate tends to be one solid color in addition to being very hard and brittle; when broken, it will form flat, smooth surfaces. Germany has several vineyards areas celebrated for their slate soils; these include the Mosel and the Rheingau—both of which also have significant outcroppings of shale (now we know why). Other wine areas rich in slate include the Clare Valley, the Cebreros VCIG (in Castilla y León), and Chile’s Aconcagua Valley.

Schist: Schist is formed (from slate or mudstone) under moderate levels of heat and pressure (metamorphic forces). Schist is identifiable by its visible “grains” (in layered formation), dull luster, and schistosity—the layer-like foliation that is found in certain coarse-grained metamorphic rocks. Despite the fact that it reminds me of a wine-geeky, made-up word (like matchsticky or porch-pounder), schistosity is a real thing.

And back to the Alpine Zone with a more entertaining take. I do admit I geeked out a bit here with Geology and truly don’t know exactly what type of rock formations those were… Shale, Slate… Shale/Schist, Slate/Schist… if you can figure it out, let me know pretty please.

Good Thingz!!!

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