Earth:Sand spike

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Short description: Bodies of calcite-cemented sandstone
Collection of museum quality sand spike specimens unearthed in Germany

Sand spikes (German: Zapfen, found within Zapfensande) are bodies of calcite-cemented sandstone in the shape of a pin[1] or mace.[2] They have primarily been found near Mount Signal around the Mexico-United States border[3][1] and in the Molasse basin in Germany.[1] They were historically classified as sand-calcite concretions, though a 2021 study argues they may be a form of seismite.[3][4][1]

Description

Sand spikes feature a bulbous cauliflower or botryoidal head that quickly tapers into a long cylindrical spike. The spikes can range in size from 1.5 inches (3.8 cm) to 3 feet (0.9 m).[5][6] They are primarily composed of quartz, feldspar and mica and are cemented by calcite.[1]

Sand spikes are found in groups generally pointing in the same horizontal direction.[2] Near Mount Signal the tails are generally pointing west, away from the San Andreas Fault.[1][6] The spikes in Germany point away from the Nördlinger Ries impact crater.[7][1]

History

Sand spikes in Germany were reported back as far as the 1820s.[1] The spikes were documented in the United States by H. W. Nichols in 1906.[8][2] While once widespread near Mount Signal, construction and other human activity has destroyed most of them.[9][1]

Formation

Multiple theories for how sand spikes form have been put forward over the years. Early explanations included that they are petrified plants or mushrooms.[4][5] They have commonly been interpreted as concretions, formed by carbonate cementation and elongated in the direction of groundwater flow.[1] A 2021 study proposed they may be a form of seismite created by intense seismic shaking caused by earthquakes or asteroid impacts.[1]

References

  1. ↑ 1.00 1.01 1.02 1.03 1.04 1.05 1.06 1.07 1.08 1.09 1.10 Buchner, Elmar; Sach, Volker J.; Schmieder, Martin (2021-11-18). "Sand spikes pinpoint powerful palaeoseismicity" (in en). Nature Communications 12 (1): 6731. doi:10.1038/s41467-021-27061-6. ISSN 2041-1723. https://www.nature.com/articles/s41467-021-27061-6. 
  2. ↑ 2.0 2.1 2.2 Garner, Kenneth B. (1936-04-01). "Concretions near Mount Signal, Lower California" (in en). American Journal of Science s5-31 (184). doi:10.2475/ajs.s5-31.184.301. https://ajsonline.org/article/61477-concretions-near-mount-signal-lower-california. 
  3. ↑ 3.0 3.1 Zinkova, Mila (2013-11-24). "Sand Spike Concretion". https://epod.usra.edu/blog/2013/11/sand-spike-concretions.html. 
  4. ↑ 4.0 4.1 Hyde, Eva May (1937). "MOUNT SIGNAL CONCRETIONS". The Mineralogist. https://insiteart.org/uploads/files/Mount-signal-concretions.pdf. 
  5. ↑ 5.0 5.1 Sanborn, William B. (1976). Oddities of the Mineral World. New York: Van Nostrand Reinhold Co.. pp. 82-83. ISBN 0442273460. https://archive.org/details/odditiesofminera0000sanb. 
  6. ↑ 6.0 6.1 Kornei, Katherine (2021-12-08). "Scientists Have a New Explanation for Mysterious Sand Spikes" (in en-US). The New York Times. ISSN 0362-4331. https://www.nytimes.com/2021/12/08/science/sand-spikes-earthquakes.html. 
  7. ↑ Landeros, Marcie (2022-01-20). "German Geologists Study Mt. Signal to Solve Mystery" (in en-US). https://calexicochronicle.com/2022/01/19/german-geologists-study-mt-signal-to-solve-mystery/. 
  8. ↑ Nichols, Henry Windsor (1906). "SAND-CALCITE CONCRETIONS FROM SALTON, CALIFORNIA.". Field Columbian Museum Geol. Ser. 3. https://allanmccollum.net/amcimages/nichols.html. 
  9. ↑ "Signs of the Imperial Valley: Sand Spikes from Mount Signal" (in en). https://insiteart.org/vital-forms/in-focus/signs-of-the-imperial-valley-sand-spikes-from-mount-signal. 



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