the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
| 30 Aug 2022
The Münsterdorf sinkhole cluster: Void origin and mechanical failure
Abstract. Since 2004, collapse sinkholes occur on the sports field of Münsterdorf, a village north of Hamburg in Germany. The sinkholes, around 2–5 m in diameter and 3–5 m deep, develop in peri-glacial sand, which in around 20 m depth is underlain by cretaceous chalk. The chalk has been pushed up close to the surface by a salt diapir. The sinkhole formation initiated suddenly and occurs with a frequency of one every two years.
We use a variety of geophysical results (e.g. gravity, electrical resistivity imaging, ground-penetrating radar) from previous field-work campaigns together with a new data set from direct-push based methods to infer mechanical and hydrological properties of the material beneath the sports field (peri-glacial sand, glacial marl, cretaceous chalk).
Based on the derived material properties, we develop a mechanical model for the sinkhole collapse, starting from simple analytical considerations and then moving towards a three-dimensional distinct-element model explaining the sudden onset of collapse sinkholes for the sports field.
The mechanical model supports our hypothesis that the sudden onset of sinkholes is triggered by changes in groundwater level.
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Notice on discussion status
The requested preprint has a corresponding peer-reviewed final revised paper. You are encouraged to refer to the final revised version.
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Preprint
(7613 KB)
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The requested preprint has a corresponding peer-reviewed final revised paper. You are encouraged to refer to the final revised version.
- Preprint
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- Final revised paper
Journal article(s) based on this preprint
Interactive discussion
Status: closed
-
RC1: 'Comment on egusphere-2022-668', Anonymous Referee #1, 23 Sep 2022
The manuscript deals with a sinkhole cluster on the sports field of MuÌnsterdorf, a village north of Hamburg in Germany, examined through geophysical surveys and mechanical models. The topic is certainly of interest to Solid Earth.
I have listed in the accompanying file a number of small edits, and requests of clarification on some issues that are not clear to me. Overall, I therefore require moderate revisions and invite the Authors to carefully read my comments on the pdf file. Here, I just summarize the main points where the Authors should make an effort to further improve the quality and clarity of the paper.
Line 33-34: I disagree with what stated. Suffosion sinkholes do not belong to the category of collapse sinkholes but are formed by different processes. Authors are kindly invited to have a look at the classification proposed by Gutierrez et al. (2014), recently revised by Parise (2019, 2022).
References:
Gutierrez F., Parise M., De Waele J. & Jourde H., 2014, A review on natural and human-induced geohazards and impacts in karst. Earth Science Reviews, vol. 138, p. 61-88, doi: 10.1016/j.earscirev.2014.08.002.
Parise M., 2019, Sinkholes. In: White W.B., Culver D.C. & Pipan T. (Eds.), Encyclopedia of Caves. Academic Press, Elsevier, 3rd edition, ISBN ISBN 978-0-12-814124-3, p. 934-942.
Parise M., 2022, Sinkholes, Subsidence and Related Mass Movements. In: Shroder J.J.F. (Ed.), Treatise on Geomorphology, vol. 5. Elsevier, Academic Press, pp. 200–220. https://dx.doi.org/10.1016/B978-0-12-818234- 5.00029-8. ISBN: 9780128182345.
Lines 76-77: it is reported that “In the mines, numerous karst features can be observed, such as dissolutionally-enlarged fissures and bedding planes and small collapse sinkholes”. One figure, with two or more pictures, to show these features and their size could be useful to readers.
Still as regards figures, no photo of the sinkholes is provided. I would appreciate adding one figure with some pictures to show the main characters of the phenomena.
Lines 91-92: about the depth of the water table, it would be interesting to know at what depth it is, and if water fluctuations in response to rainfall occur. Some more information should be provided at this regard.
Lines 125 and following (3.2. Hypotheses): both presented hypothesis start from the presence of an underground void. What if the void was not present, and the sinkholes are not of collapse origin? Is there the possibility of suffusion sinkholes? The lack of photographs of the sinkholes make difficult to understand if this third hypothesis could be true. In any case, why do you suppose the presence of voids for the sinkhole formation?
This is the main problem I see in this article, since it is assumed that a void is present, and the possibility of a different typology of sinkholes is not taken into consideration at all. Authors should clarify the reasons why they consider only the presence of voids (either in the peri-glacial sand or in the chalk), excluding the other possibility.
For all the considerations above, I recommend major revision.
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AC1: 'Reply on RC1', Georg Kaufmann, 07 Oct 2022
We would like to thank the anonymous referee 1 for discussion and
helpful comments. We will consider all minor edits and clarifications
made by the referee in the accompanying file.Here, we take the opportunity to reply to the four main concerns
listed by referee 1:1. Suffosion sinkholes
We agree with the referee that suffosion sinkholes do not fall into
the collapse-sinkhole category. We have corrected this mistake and
added the three citations to more recent publications concerning
the classification of sinkholes.We will, in the revised version, also clarify, that the Münsterdorf
sinkholes are somewhere between the end members cover-collapse and
caprock-collapse sinkholes.2. Photos of site(s)
The referee asks for photos of the site and the karst features
in the nearby open-pit mines. We will add a photo of a sinkhole
just next to the sports field for clarification (see attachment). However, as we
have no access to the private open-pit mine, we can only refer
to photos in other (unpublished) publications concerning the
karst features in the mine.3. Water table
We will extend the section of the water table, adding both absolute
numbers from the past and present time, and about the fluctuctions
induced by rainfall.4. Suffosion sinkhole
The referee asks for the reason why we start proposing an
initial void as cause for the sinkholes. Basically we have three
lines of evidence, pointing us to a collapse sinkhole:- The occurence and the initial shape of the sinkholes, both sudden and near-vertical, points to a sudden collapse, and not slow suffosion.
- Also the size of the sinkholes, 3 meter diameter and 4-5 meter deep, thus a volume of around 30-35 cubic meter, needs a larger volume in the sub-surface.
- There are several collapse sinkholes in the area, which are much older than the sinkhole cluster of the sports field.
-
AC1: 'Reply on RC1', Georg Kaufmann, 07 Oct 2022
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RC2: 'Comment on egusphere-2022-668', Anonymous Referee #2, 10 Oct 2022
The paper deals with an interesting aspect of the application of geophysical investigations and modelling for the understanding of genesis and the exploration of sinkholes of the locality Münsterdorf. The focus is on the use of results from direct push soundings and geophysical explorations for the numerical modelling of the formation of sinkholes. The publication of the paper is supported in any case, but some minor but substantial changes or additions are required:
Previous geophysical measurements
Various assumptions about the geological structure of the subsurface come from earlier geophysical investigations, which unfortunately only briefly described. A table with the measurements carried out so far with reference to literature should be added.
Forward Modeling
From the reviewer's point of view, two overly simplified model calculations for the detectability of cavities by means of gravimetry and geoelectrics are presented. In addition, the rock physical parameters used must be checked for consistency in the paper. For example, some of the resistivities used for modeling do not match the values given in Table 1. Furthermore, the effect of the described glazial till layers was not taken into account, although these influence the density distribution and resistivity distribution in the subsurface.
This section should be supplemented by geophysical measurement examples for gravimetry and geoelectrics from the investigation area. If this is not possible, the section can also be omitted.
Drop of the groundwater level as an initial event
The drop of the groundwater surface causes the formation of earth falls. The hypothesis is explained in detail and comprehensibly. However, there is a lack of information on the past and present location of the groundwater surface as well as on the course of the groundwater surface between the study area and the opencast mine. In Figure 11, information on the location and topographical height of the stör river and the opencast mine as well as the distance between the objects must be supplemented to scale. Is a lowering of the groundwater level by several meters away from the opencast mine really realistic and what role does the mentioned fault zone on which the sinkholes are located play?
Citation: https://doi.org/10.5194/egusphere-2022-668-RC2 -
AC2: 'Reply on RC2', Georg Kaufmann, 01 Nov 2022
We would like to thank the anonymous referee 2 for discussion and
helpful comments. We will consider all clarifications made by the referee.Here, we take the opportunity to reply to the three main concerns
listed by referee 2:1. Previous geophysical measurements
We will add a table summarizing all previous geophysical measurements.
2. Forward modeling
We will cross-check all material parameter values, and correct
wrong values in table 1.We did not consider the glacial till layer in the forward model for two
reasons:- The glacial till layer peters out in the sinkhole zone.
- The electrical resistivity values of the till and the wet chalk are similar.
We will mention these two points in a revision.
3. Drop of the groundwater level as an initial event
The drop of groundwater level due to pumping in the open-pit mine
is modelled with a large-scale model with simple setup. The modelled
drop in groundwater level by several meters, forcasted by the model,
has been observed in boreholes on and around the sports field. We
will make this a bit more clear in the section on groundwater levels
(A similar remark has been made by referee 1).Citation: https://doi.org/10.5194/egusphere-2022-668-AC2
-
AC2: 'Reply on RC2', Georg Kaufmann, 01 Nov 2022
Interactive discussion
Status: closed
-
RC1: 'Comment on egusphere-2022-668', Anonymous Referee #1, 23 Sep 2022
The manuscript deals with a sinkhole cluster on the sports field of MuÌnsterdorf, a village north of Hamburg in Germany, examined through geophysical surveys and mechanical models. The topic is certainly of interest to Solid Earth.
I have listed in the accompanying file a number of small edits, and requests of clarification on some issues that are not clear to me. Overall, I therefore require moderate revisions and invite the Authors to carefully read my comments on the pdf file. Here, I just summarize the main points where the Authors should make an effort to further improve the quality and clarity of the paper.
Line 33-34: I disagree with what stated. Suffosion sinkholes do not belong to the category of collapse sinkholes but are formed by different processes. Authors are kindly invited to have a look at the classification proposed by Gutierrez et al. (2014), recently revised by Parise (2019, 2022).
References:
Gutierrez F., Parise M., De Waele J. & Jourde H., 2014, A review on natural and human-induced geohazards and impacts in karst. Earth Science Reviews, vol. 138, p. 61-88, doi: 10.1016/j.earscirev.2014.08.002.
Parise M., 2019, Sinkholes. In: White W.B., Culver D.C. & Pipan T. (Eds.), Encyclopedia of Caves. Academic Press, Elsevier, 3rd edition, ISBN ISBN 978-0-12-814124-3, p. 934-942.
Parise M., 2022, Sinkholes, Subsidence and Related Mass Movements. In: Shroder J.J.F. (Ed.), Treatise on Geomorphology, vol. 5. Elsevier, Academic Press, pp. 200–220. https://dx.doi.org/10.1016/B978-0-12-818234- 5.00029-8. ISBN: 9780128182345.
Lines 76-77: it is reported that “In the mines, numerous karst features can be observed, such as dissolutionally-enlarged fissures and bedding planes and small collapse sinkholes”. One figure, with two or more pictures, to show these features and their size could be useful to readers.
Still as regards figures, no photo of the sinkholes is provided. I would appreciate adding one figure with some pictures to show the main characters of the phenomena.
Lines 91-92: about the depth of the water table, it would be interesting to know at what depth it is, and if water fluctuations in response to rainfall occur. Some more information should be provided at this regard.
Lines 125 and following (3.2. Hypotheses): both presented hypothesis start from the presence of an underground void. What if the void was not present, and the sinkholes are not of collapse origin? Is there the possibility of suffusion sinkholes? The lack of photographs of the sinkholes make difficult to understand if this third hypothesis could be true. In any case, why do you suppose the presence of voids for the sinkhole formation?
This is the main problem I see in this article, since it is assumed that a void is present, and the possibility of a different typology of sinkholes is not taken into consideration at all. Authors should clarify the reasons why they consider only the presence of voids (either in the peri-glacial sand or in the chalk), excluding the other possibility.
For all the considerations above, I recommend major revision.
-
AC1: 'Reply on RC1', Georg Kaufmann, 07 Oct 2022
We would like to thank the anonymous referee 1 for discussion and
helpful comments. We will consider all minor edits and clarifications
made by the referee in the accompanying file.Here, we take the opportunity to reply to the four main concerns
listed by referee 1:1. Suffosion sinkholes
We agree with the referee that suffosion sinkholes do not fall into
the collapse-sinkhole category. We have corrected this mistake and
added the three citations to more recent publications concerning
the classification of sinkholes.We will, in the revised version, also clarify, that the Münsterdorf
sinkholes are somewhere between the end members cover-collapse and
caprock-collapse sinkholes.2. Photos of site(s)
The referee asks for photos of the site and the karst features
in the nearby open-pit mines. We will add a photo of a sinkhole
just next to the sports field for clarification (see attachment). However, as we
have no access to the private open-pit mine, we can only refer
to photos in other (unpublished) publications concerning the
karst features in the mine.3. Water table
We will extend the section of the water table, adding both absolute
numbers from the past and present time, and about the fluctuctions
induced by rainfall.4. Suffosion sinkhole
The referee asks for the reason why we start proposing an
initial void as cause for the sinkholes. Basically we have three
lines of evidence, pointing us to a collapse sinkhole:- The occurence and the initial shape of the sinkholes, both sudden and near-vertical, points to a sudden collapse, and not slow suffosion.
- Also the size of the sinkholes, 3 meter diameter and 4-5 meter deep, thus a volume of around 30-35 cubic meter, needs a larger volume in the sub-surface.
- There are several collapse sinkholes in the area, which are much older than the sinkhole cluster of the sports field.
-
AC1: 'Reply on RC1', Georg Kaufmann, 07 Oct 2022
-
RC2: 'Comment on egusphere-2022-668', Anonymous Referee #2, 10 Oct 2022
The paper deals with an interesting aspect of the application of geophysical investigations and modelling for the understanding of genesis and the exploration of sinkholes of the locality Münsterdorf. The focus is on the use of results from direct push soundings and geophysical explorations for the numerical modelling of the formation of sinkholes. The publication of the paper is supported in any case, but some minor but substantial changes or additions are required:
Previous geophysical measurements
Various assumptions about the geological structure of the subsurface come from earlier geophysical investigations, which unfortunately only briefly described. A table with the measurements carried out so far with reference to literature should be added.
Forward Modeling
From the reviewer's point of view, two overly simplified model calculations for the detectability of cavities by means of gravimetry and geoelectrics are presented. In addition, the rock physical parameters used must be checked for consistency in the paper. For example, some of the resistivities used for modeling do not match the values given in Table 1. Furthermore, the effect of the described glazial till layers was not taken into account, although these influence the density distribution and resistivity distribution in the subsurface.
This section should be supplemented by geophysical measurement examples for gravimetry and geoelectrics from the investigation area. If this is not possible, the section can also be omitted.
Drop of the groundwater level as an initial event
The drop of the groundwater surface causes the formation of earth falls. The hypothesis is explained in detail and comprehensibly. However, there is a lack of information on the past and present location of the groundwater surface as well as on the course of the groundwater surface between the study area and the opencast mine. In Figure 11, information on the location and topographical height of the stör river and the opencast mine as well as the distance between the objects must be supplemented to scale. Is a lowering of the groundwater level by several meters away from the opencast mine really realistic and what role does the mentioned fault zone on which the sinkholes are located play?
Citation: https://doi.org/10.5194/egusphere-2022-668-RC2 -
AC2: 'Reply on RC2', Georg Kaufmann, 01 Nov 2022
We would like to thank the anonymous referee 2 for discussion and
helpful comments. We will consider all clarifications made by the referee.Here, we take the opportunity to reply to the three main concerns
listed by referee 2:1. Previous geophysical measurements
We will add a table summarizing all previous geophysical measurements.
2. Forward modeling
We will cross-check all material parameter values, and correct
wrong values in table 1.We did not consider the glacial till layer in the forward model for two
reasons:- The glacial till layer peters out in the sinkhole zone.
- The electrical resistivity values of the till and the wet chalk are similar.
We will mention these two points in a revision.
3. Drop of the groundwater level as an initial event
The drop of groundwater level due to pumping in the open-pit mine
is modelled with a large-scale model with simple setup. The modelled
drop in groundwater level by several meters, forcasted by the model,
has been observed in boreholes on and around the sports field. We
will make this a bit more clear in the section on groundwater levels
(A similar remark has been made by referee 1).Citation: https://doi.org/10.5194/egusphere-2022-668-AC2
-
AC2: 'Reply on RC2', Georg Kaufmann, 01 Nov 2022
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Georg Kaufmann
Douchko Romanov
Ulrike Werban
Thomas Vienken
The requested preprint has a corresponding peer-reviewed final revised paper. You are encouraged to refer to the final revised version.
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