About
TrailheadGeological Trail Intro Part 2
What you'll see 🌊 River or creek

Green Creek Complex The Green Creek Complex is an assemblage of metamorphic rocks consisting of granite, granitic gneiss (metamorphosed granite), schist and a few other rock types. Radiometric analysis indicates that the Green Creek granite may be as old as 2.5 billion years ( Archean ) and is considered to be some of the oldest rock exposed on the continent west of the Mississippi River. This granite has a porphyritic texture, meaning it is composed of crystals of two distinct sizes.The larger crystals are potassium feldspar. They are embedded in a matrix of smaller crystals consisting of quartz, biotite, and plagioclase feldspar. Feldspars are the most common family of silicate minerals. They are broadly divided into two groups: sodium and calcium bearing feldspars, called plagioclase, and potassium bearing feldspars, called orthoclase, microcline or sanidine, depending on their crystallographic structure.

Location

Geological Trail Intro Part 2

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Trail data: USGS National Map / PAD-US, the National Park Service, state agencies, and © OpenStreetMap contributors (ODbL). Access and conditions change — check with the managing agency before you go.