United States Meteorite Impact Craters

Crooked Creek Impact Crater, Missouri

The Crooked Creek impact structure is a 6-7 km diameter or slightly larger complex crater located in southwestern Crawford County, Missouri, at approximately N 37° 50' by W 91°23' or (91.39485 degrees west, 37.83496 degrees north) (Mulvany, 2004).  The crater is revealed on the Cook Station and Cherryville USGS 7.5 minute quadrangle maps.  Important geological maps of the structure have been published by Hughes (1912), Hendriks (1954), and Mulvany (2004).  The site is easily accessed. State Rte VV bisects the crater on the west side, with several smaller roads cross-cutting the area as well.  The eastern side of the craters is disected from north to south by Crooked Creek, which exposes many areas of the bedrock affected by the impact.

Evidence of Impact Origin

The impact origin of each location listed on this website has been supported by unambiguous diagnostic evidence of hypervelocity impact that has been reported in a scientific (usually peer reviewed) context.  Without such evidence, a geological structure is not a confirmed impact crater.  This section, which is included for each crater on this website, is not an exhaustive list of such published evidence, but is meant to demonstrate that appropriate work has been done for each listing.

see: Dietz and Lambert, 1980; Hendriks, 1954.

• planar deformation features in quartz (up to 4 sets, indexed)
• shatter cones

Other significant evidence: detailed mapping, morphologic and morphometric data, impact melt lithologies, breccia. 

The diameter of the site is generally listed as about 7 km based on the work of Hendriks, 1954, but may be close to 9 km based on GIS work by Nickerson, 2002 (unpublished MS thesis referenced by the more easily available Mulvany, 2004).  Using the work of Norton, 2002, and the above estimate of diameter, Mulvany described a probably iron-nickel impactor with a diameter of about 250 meters and mass of about 65 billion kilograms.

The overall shape of the structure consists of a raised ring shaped central uplift (anticline) region about 2.5 km in diameter with a slightly depressed center.  The central uplift region is composed of rebounded strata elevated in excess of 300 meters (1000 feet) (Hendriks, 1954) above their original position.  Surrounding the upraised central basin and ring is a much larger depressed ring about 2 to 3 km in width that was left by both the impact excavation of material and by downward and inward flow of mass, in compensation for uplift, during crater modification.  Beyond this depressed ring, Hendriks and other investigators report a resumption of the nearly horizontal bedding characteristic of the surrounding region.

Complex faulting, both radially from the center and in concentric circles surrounding it, underpin these surface expressions.  The faults result from large scale heaving and displacement as temporarily fluidized solid rocks compensated and fractured at every scale, from grain to kilometer, in response to the massive energy release of the impact.  Faulting has been examined in some detail by Hendriks, 1954, and the nature of compensation in smaller scale folding was examined in some detail by Kenkmann in 2001 and 2002.

Discovery by Hughes, 1910 to 1912

The Crooked Creek impact structure was first described in 1910 (though not as an impact crater) by representatives of the Missouri Bureau of Geology and Mines who were assessing Crawford County for possible economically recoverable ores.  (Hughes, 1912)  The first publication of the site, a brief description and rough map, was by Hughes, 1911.  Hughes mapped and described the structure in more detail the next year (1912), producing a foundational piece of research in the context of an unpublished undergraduate thesis.  He identified the outcropping rock units, associated them to known ore producing exposures closer to the St. Francois Mtns., and produced a basic geological surface map of the area of the structure.  In his map and accompanying description, Hughes observed upon the raised Potosi dolomite strata in the center of the structure, noting an up to 700 ft. vertical displacement of the surrounding Davis formation, identified and characterized the surrounding graben structure, and noted the succession and geometry of the surrounding exposures.  He also comments on the presence of several small mines that were active or abandoned within the bounds of the structure at the time of his work.  These had produced small amounts of lead, iron, barite, coal, and fire clay.  Many of Hughes' observations were based on rock exposures in digs that were open at the site at the time of his work.

The first major study of the structure was performed between 1942 and 1950 by Herbert Hendriks, who made an interest in the site a major part of his doctoral thesis work.  He described the site in much greater detail than the previous work and interpreted it as a meteorite impact by crater.  The site has subsequently been studied by numerous other authors.  Hendriks conclusion of impact origin has been supported by most authors within the last 50 years.

Maps, produced by Hughes in 1911 and 12, were dramatically improved upon by Hendriks in 1954. Two maps produced by Hendriks have been combined by Mulvany, 2004, to yield a very good map of the location that is available from the Missouri Geological Survey.

This photo was taken looking west from Yankee Br Rd towards a portion of the central uplift of the crater.  The farmed floodplain of the river, which has cut through the annlar basin and partially encircled the uplift, creates a nice, flat contrasting surface on the east side of the crater, which makes the central uplift area stand out.  It is difficult to visually distinguish the uplift from other directions within the crater.  Immediately behind my back, from the vantage of this photo, is an eroded wall of deformed megabreccia.  It is a very steep hillside that extends off to the north and south, and rests well inside the crater rim.
In this photo, taken at the low water crossing on Beers road in the northeast quadrant of the crater, Jerri Stevens points at impact tilted bedding of what is probably Gasconade dolomite.  Previous investigators captured cores for paleomagnetic studies at this location.

The surface of Crooked Creek crater is substantially eroded.  In addition to removal of the top layers of impacted rock, Evans, 2007, and others have noted that substantial overlying rock may have been removed in millenia subsequent to the impact, including much of the original surface of the central uplift.  Younger overlying sediments that post-date the impact are represented only in occasional outliers of more recent sandstone or small coal deposits that are strewn about the crater.  This photo shows one of many boulders of brecciated chert, dolomite, and roubidoux sandstone that are scattered along state road VV along the west side of the crater.

University of Arkansas geoscience and space science graduate students and faculty examine an impactite outcrop just to the northwest of the central uplift.  A large slab of Roubidoux sandstone, in the foreground, gives way to finely brecciated carbonate and chert at the far end of the group.

I always find it a bit tricky trying to visualize, from a ground perspective, how roads and intersections relate to the morphology of a crater.  I hope this helps others to overcome this challenge.  The crater rim and central uplift are only approximate, but are not very far off.  The central uplift is somewhat larger than actual. 

Crater Age

The earth impact database (see link below) lists the structure as about 320 million years old, plus or minus 80 million years.

Hendriks, 1954, observed that the disturbed rock resulting from the Crooked Creek impact includes the Jefferson City dolomite (lower Ordovician). He also observed what he believed to be undisterbed Pennsylvanian sandstone and remainders (boulders) of weathered in-situ Pennsylvanian sandstone at various locations throughout the site. Based on this, Hendriks concludes an age between the Lower Ordovician and the Pennsylvanian for this structure. Subsequent distinctions summarized in Mulvaney, 2004, seem to narrow this to the Ordovician to pre-Pennsylvanian (or Mississippian).

Miller et al., in 2006 and 2007, GSA abstracts, reported on Lower Ordovician conodonts and a late Osagean Mississippian brachiopod found in a float block of breccia, suggesting an age between the late regional Osagean (late Tournasian) and Pennsylvanian.

Crooked Creek Crater Geology

The Crooked Creek impact crater is expressed in Cambrian and Ordovician carbonates and sandstone of the Salem Plateau in the Ozark Plateaus geologic region. (Hendriks, 1954, and others) The sedimentary rocks in which the impact is preserved are notably flat lying in the surrounding regions (described as layer-cake geology - about 2.8 m. tilt per km.), making the contrasting disruptions of the impact site all the more dramatic. Kiilsgaard et al., 1962, notes that the direction of dip of the Cambrian and Ordovician units is to the northwest.

The Crooked Creek impact rests in sedimentary layers overlying a Cambrian igneous basement, related to that which is exposed in the St. Francois Mtns.  This foundation is overlain by a sequence of Late Cambrian and Ordovician to Pennsylvanian sedimentary carbonates, sandstones, cherts, and shales.  The sedimentary layers result from a series of transgressions of the sea, and are separated by several continental unconformities (points in the succession where the land surface was exposed and eroded). The underlying Cambrian igneous basement (about 1.485 to 1.350 billion years old, Spavinaw terrane) is not exposed within or near the structure.  According to Hendriks, 1954, the basal sedimentary layer of the region, the arkosic LaMotte Sandstone, derived from the igneous basement, is not exposed in the region either, and the immediately subsequent late-Cambrian Bonnterre Formation is the earliest material found within the exposed rocks of the central uplift.

Specific stratigraphy of the site is discussed, briefly but clearly, in Mulvany, 2004, where it is encapsulated from the work of Hendriks, 1949 and 1954.  Hendriks notes exposures from the Cambrian to Pennsylvanian, with Pleistocene and more recent soils and gravel overlying the bedrock.

Kenkmann, 2001 and 2002, offered insights regarding timing and rate of deformation.  He concludes a period of crater modification (collapse) for the entire location of 20 to 30 seconds, based on numerical models, and then looked at how apparently-plastic folds were accomplished at 50 to 100 meter/second.  In his 2001 LPSC abstract and subsequent 2002 article in Geology, Kenkmann revealed that macro-scale accomodation to motion, in what appear to be plastic folds, is actually accomplished by micro-scale brittle deformation at the submillimeter grain to cm scale... ie: by lots of little cracks that add up to the larger motion.

Kenkmann, in artful brevity, describes the overall structure in the following terms, "Bounded by a series of normal faults, the structure consists of a peripheral ring syncline that in turn circles a heavily faulted central uplift. The oldest beds are exposed along a ring anticline of the central uplifted more than 300 m above their normal position (Hendriks, 1954). The innermost part of the central uplift appears to be downfaulted and collapsed."

Faulting in the Area

Aside from the ring grabens and radial faults associated with the structure itself, Kiilsgaard et al., 1962, points out that the site is at the west end of the Palmer fault zone, and is about 10 miles south of the mapped extent of the north-south trending Cuba fault.  Kiilsgaard offers a small map of the crater in the context of regional faults, and attributes the structure to fault related explosion.  Both previously and subsequently to this, Hendriks, 1954, and others have supported the position that faulting post-dates the impact crater.

Shatter Cones

This site was pivotal in the development of the understanding of shatter cones as a diagnostic signature of impact processes.  This theme was primarily developed in a series of articles by Dietz, in the very late 50s and early 60s.  Shattercones have been observed by multiple authors and researchers working in the central uplift area of the crater, including Kiilsgaard, et al, 1962, who mapped several locations distributed over an area of a square kilometer or so.

Mineralization and Mining

Both Kiilsgaard et al., 1962, and Hendriks, 1954, detail mining of barite (several thousand tons) and galena ('small tonnage') that have taken place within the crater, along with minor quantities of several other sulfide ore minerals. Mention of these minerals in the context of quartz veins and clays, some located within brecciated zones, suggests hydrothermal emplacement at some point subsequent to impact.  Kiilsgaard et al, 1962, points this out by noting that the mineral crystals seem to show no damage from the brecciating event or from motion along the Palmer fault, where they observe the mining operations and mineralization to be concentrated.

Bibliography and References:

(If links to articles don't work, don't give up. Try pasting the link shown into a search engine or searching for the article authors, title, or other reference information.  If your research leads you to additional scientific references related to this crater, please help improve this resource by sending a note with the new citation(s) to: )

Amstutz, G. C. 1965. A morphological comparison of diagenetic cone-in-cone structures and shatter cones. Annals of the New York Academy of Sciences.

• Field Trip 1: Weaubleau Osceola
• Field Trip 2: Decaturville and Crooked Creek

no current link found

Evans, K. R., 2007, A Tattered Tapestry: Interpreting Remote Sensing Imagery of the Ozark Mountains, 2007 Annual Meeting, Geological Society of America, Abstracts with Programs, Vol. 39, No. 3, p. 64.

(Both Crooked Creek and Decaturville have had substantial overlying sediment removed by erosion.)

Finn, Michael P., Gary W. Krizanich, Kevin R. Evans, Melissa R. Cox, and Kristina H. Yamamoto (2012). Visualizing Impact Structures Using High-Resolution LiDAR Derived DEMs: A Case Study of Two Structures in Missouri. Surveying and Land Information Science, Vol. 72, No. 2, pp. 87 - 97

Finn, Michael P., Gary W. Krizanich, Kevin R. Evans, and E. Lynn Usery (2007). Contemporary High-Resolution LiDAR Derived DEMs Could Inspire Developments in the Study of Impact Structures. Proceedings of the Association of American Geographers/ Great Plains and Rocky Mountain Section Annual Meeting, Denver, CO

Finn, Michael P., Gary W. Krizanich, and E. Lynn Usery (2007). Contemporary High-Resolution LiDAR Derived DEMs Could Inspire Developments in the Study of Impact Structures. Proceedings of the International Union of Geodesy and Geophysics XXIV General Assembly, Perugia, Italy, p. 408-409

Fox, J. H., 1970. Geophysical investigation of the Crooked Creek, Missouri, cryptoexplosion structure (abstract). EOS, v. 51, p. 770.

(A one paragraph encapsulation of the BellComm article published by Fox in the same year (1970). Summary of his magnetic and gravity survey of 1954 - attributes the Crooked Creek structure to a gas explosion at the (uncertain) intersection of the Palmer and Cuba faults.)

Fox, J. H., The geophysical signature associated with a cryptoexplosion structure. Case 103-7, Bell Comm., Inc. 13 p. 1970.

no link found

(Gravimetric and magnetic surveys of the region (1954) suggest the presence of the Palmer Fault extending from the west side of the structure and weakly supports an extension of the Cuba fault from its known terminus 15 to 20 miles to the north. Interprets the structure as a gas explosion at the (uncertain) intersection of these two faults. Also observes that the structure is very deep.  Notes that the 1954 gravity and magnetic survey maps were deposited in the Rolla library of the Missouri Geological Survey.)

Fox, J. H., Allen V. T., and Heinrich, R. R., 1954, Crooked Creek cryptovolcanic structure, Steelville, Missouri [abs.]. Geological Society of America Bulletin, 65(12), part 2, p. 1252-1253.

no link found

Grieve, R. A. F., Masaitis, V. L., The economic potential of terrestrial impact craters. International Geology Review, v. 36, pp. 105-151. 1994.

Hendriks, H. E., 1949, Geology of the Crooked Creek area, Missouri. Unpublished doctorate dissertation, State University of Iowa, Iowa City, Iowa, 234 pp.

no link found

Hendriks, H. E., 1954, Geology of the Steelville Quadrangle, Missouri. Missouri Geological Survey and Water Resources, Volume 36, Second Series, 88 pp. (with 2 geological maps)

no link found

Heyl, A. V., 1983, Some major lineaments reflecting deep-seated fracture zones in the central United States, and mineral districts related to the zones. Global Tectonics and Metallogeny, 2, p. 75-89.

Heyl, A. V., 1972, The 38th parallel lineament and its relationship to ore deposits. Economic Geology, 67, p. 879-894.

Hughes, V.H., 1911, Reconnaissance work: Crawford County. Missouri Bureau of Geology and Mines, Biennial Report [1909-1910] of the State Geologist to the Forty-Sixth General Assembly, p. 48-54.

(The earliest published report of the structure.)

Hughes, V. H., 1912, The geology of a complexly folded area on Crooked Creek in Crawford County, Missouri. Unpublished undergraduate thesis, Missouri School of Mines and Metallurgy, Rolla, Missouri, 18 pp.

(Hughes spent a great deal of time in the field, at the site. He benefited substantially from being present during a period when active professional prospecting was underway within the structure, and when many previous shallow mines and prospecting digs still made rock exposures available. Hughes produced the first good geological map of the area, described the structure's morphology in some detail, identified the associated rock units, and placed them within the surrounding regional context. He made no comments regarding origin of the structure, but produced a remarkable piece of descriptive geological literature.)

Kenkmann, T., 2001, Deformation mechanisms during impact crater modification inferred from the Crooked Creek impact structure, Missouri, USA. 32nd Annual Lunar and Planetary Science Conference, Abstract 1560.

(Preliminary summary of 2002 brief in Geology.  Uses a folded specimen as a window on understanding small scale accomodation to movement during rapid deformation of rock masses during crater formation and uses numerical models to establish an approximate initial modification (collapse) stage for the crater of 20 seconds at 50 to 100 meters/sec. Microstructures, examined in thin section, are interpreted in terms of their contribution to macroscopic deformation.)

Kenkmann, T., 2002, Folding within seconds. Geology, March 2002; vol. 30, no. 3, p 231-234.

(Adds to our understanding of the mechanism of accommodation to motion in the abruptly mobilized rocks at large impact sites. Reveals that apparently-plastic deformation is accomplished by brittle deformation at the microscopic scale, with overall gross movement accounted for by the accumulated effects of closely spaced mm to cm scale microfaulting.)

Kisvarsanyi, E. B. and Hebrank, A. W., 1982, Guidebook A: field trip to the St. Francois Mountains and the historic Bonne Terre Mine. Missouri Department of Natural Resources, Division of Geology and Land Survey, Open File Report 82-16-MR, p. 7-8.

Kiilsgaard, T. H., Heyl, A. V. and Brock, M. R., 1962, The Crooked Creek disturbance, southeast Missouri. U.S. Geological Survey Professional Paper 450-E, p. E14-E19.

(Kiilsgaard et al, 1962, attempts to refute the work of Dietz and Hendriks, who had substantially advanced the understanding of the site's impact origins.  They argue that the structure was caused by a steam explosion from buildup of hot gasses at the intersection (which may not exist) of the Cuba and Palmer faults. Though wrong, they took a close look at small scale rock features, and inadvertantly gave some of the earliest descriptions of impactite variability in relation to mode of implacement. They also provide an interesting constraint on timing, by recording that fault associated mineralization showed no evidence of damage by brecciation or damage by fault movement.)

Snyder, F. G., Beveridge, T. R., Gerdemann, P. E., Hendriks, H. E., Fellows, L., 1964, Cryptovolcanic structures of south central Missouri. Guidebook, Eleventh Annual Field Trip of the Association of Missouri Geologists, 11 p.

Snyder, F.G, Gerdemann, P.E., Hendriks, H.E., Williams, J.H., Wallace, G., and Martin, J.A., 1965, Cryptoexplosive structures in Missouri: Guidebook, 1965 Annual Meeting of the Geological Society of America: Geological Survey and Water Resources Report of Investigations, No. 30, 73 pp.

Woodbury, C. E., 1987, A gravity and magnetic study of the Crooked Creek crypto-explosion structure, Crawford County, Missouri. Unpublished thesis, Univ. of Missouri-Rolla, Rolla, Missouri, 79 p.

Woodbury, C. E., and Corry, C. E., 1987, Gravity and magnetic surveys of the Crooked Creek impact structure, Crawford County, Missouri: Geological Society of America Abstracts with Programs, v. 19, no. 7, p. 896.

no link found

Crooked Creek Maps:

Maps of the structure have been published by (among others) Hughes, 1912; Hendriks, 1954; Mulvany, 2004.