Blue goo

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Blue goo is a sticky, plasticky, blueish-grey, clay-textured soil derived from a highly weathered serpentinite mélange.[1][2] The name derives from the soil's color; a result of undergoing anaerobic conditions and becoming gleyed.[3] A greyer variation is called "grey goo".[2] Blue goo is primarily found along the Northern California coast.[2]

Parent material[edit]

The Franciscan Complex is the bedrock from which blue goo is derived.[1] It stretches along the coastline from Central California up to Southern Oregon and contains sheared materials from both the Pacific and North American Plates that have accumulated in the accretionary wedge.[1]

The rock types that produce blue goo include: greenstones, cherts, basalts, shales, sandstones, schists, and serpenitites.[1][2][4][5][6] These materials mixed together forming a "plum pudding" or a mélange.[1][2] This mélange decomposed through weathering to form blue goo.[7]

Common features[edit]

Clay soils like blue goo have the highest water-holding capacity when compared with other soils, giving them a low draining capacity.[3] This kind of habitat is unsuitable for most plants,[3] but the Northern California coastline maintains high levels of vegetation year round.

Due to blue goo's clayey texture, it slips when overly saturated.[6] This slippage is increased in heavy rainfall areas and in shallow soils; deep soils have more total pore space and are not as prone to slippage.[3] These features contribute to the landslide-ridden environments found along the Northern Californian coast.[5][6]


The Franciscan Complex, from which blue goo is derived, extends from Central California up the coast through parts of Southern Oregon.[1] But blue goo has only been found in two Northern Californian regions located in Humboldt County: the Trinidad region and the Orick region. Blue goo is thought to also be found in the Eel River region and along the Southern Oregon coastline.


  1. ^ a b c d e f Aalto, Ken R. (1976). "Sedimentology of a Melange: Franciscan of Trinidad, California". Journal of Sedimentary Petrology. 46 (4): 913–929. doi:10.1306/212F7090-2B24-11D7-8648000102C1865D.
  2. ^ a b c d e Department of Geology. Humboldt State University. "Trinidad Lab Manual" (PDF).
  3. ^ a b c d Brady, Nyle C.; Weil, Ray R. (2008). The Nature and Properties of Soils (14 ed.). Upper Saddle River, NJ: Pearson-Prentice Hall. p. 990.
  4. ^ "Geology of Eel River Valley area, Humboldt County, California : Ogle, Burdette Adrian : Free Download & Streaming". Internet Archive. Retrieved December 17, 2015.
  5. ^ a b Tula, Alex (1972). "Franciscan Geology at Patrick's Point, California". Senior Thesis. Department of Geology. Humboldt State University.
  6. ^ a b c Gustason, Edmund R. (1979). "Earthflow Movement Characteristics at Truttman Sink: A Franciscan Complex Mélange Coastal Headland". Senior Thesis. Department of Geology. Humboldt State University.
  7. ^ Anderson, Leslie S. (2011). Unearthing Evidence of Creatures from Deep Time: A Beginner's Fossil Guide to the Northern California Coast (PDF). Humboldt State University. p. 6. Retrieved January 17, 2016.