Geomorphological Data from Detonation Craters in the Fehmarn Belt, German Baltic Sea

Abstract

Military munitions from World War I and II dumped at the seafloor are a threat to the marine environment and its users. Decades of saltwater exposure make the explosives fragile and difficult to dispose of. If required, the munition is blast-in-place. In August 2019, 42 ground mines were detonated in a controlled manner underwater during a NATO maneuver in the German Natura2000 Special Area of Conservation Fehmarn Belt, the Baltic Sea. In June 2020, four detonation craters were investigated with a multibeam echosounder for the first time. This dataset is represented here as maps of bathymetry, slope angle, and height difference to the surrounding. The circular craters were still clearly visible a year after the detonation. The diameter and depth of the structures were between 7.5–12.6 m and 0.7–2.2 m, respectively. In total, about 321 m2 of the seafloor was destroyed along the track line.

Circular structures on the seabed: differentiating between natural and anthropogenic origins—Examples from the Southwestern Baltic Sea

“…These deposits can also be seen in the video profiles, where they are evident on the walls and around the crater rim. Boulders were also observed on the rim and around the craters in video profiles (Figure 7F), as well as in bathymetric data (Papenmeier et al, 2022). None of the Class 5 craters show significantly elevated rims in any of the surveys.…”

“…The craters observed northwest of Fehmarn Island correspond to mine-blasting craters (Papenmeier et al, 2022) related to NATO maneuvers to clear 42 British mines in August 2019 (Siebert et al, 2022). The blasting affected the geological basement and the layers on top (Figure 7H), which correspond to lag deposits overlying glacial till (Feldens et al, 2015;Papenmeier et al, 2022).…”

“…Craters produced by the controlled blast in place of munition Kampmeier et al (2020), Papenmeier et al (2022).…”

“…Class 5 structures are found in lag sediments west of the Fehmarn dune field (Feldens et al, 2009), and are generally smaller in diameter but deeper than those found in Kiel Bight (Figures 7B-H). These craters were first surveyed with MBES in 2020 (Papenmeier et al, 2022) and additionally in 2021 and 2022 (this study; Figures 7B-H). There were no significant changes in crater depth between 2020 and 2021.…”

“…Some dumping sites (D.S) of dredged material are indicated in (A,C,D). Reported detonation craters in (B)(Kampmeier et al, 2020) and (C)(Papenmeier et al, 2022). Pockmarks in Eckernförde Bay (EB in the overview figure)(Whiticar and Werner, 1981;Whiticar, 2002;Schlüter et al, 2004;Hoffmann et al, 2020).…”