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| Titel |
The Structure of the Kaali Impact Crater (Estonia) based on 3D Laser Scanning, Photogrammetric Modelling and Strike and Dip Measurements |
| VerfasserIn |
Michael Zanetti, Jakob Wilk, Argo Jõeleht, Rudolf Välja, Anna Losiak, Tomek Wisniowski, Matthew Huber, Kristiina Pavel, Aivar Kriiska, Juri Plado, Wolf Dietrich Geppert, Antero Kukko, Harri Kaartinen |
| Konferenz |
EGU General Assembly 2015
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 17 (2015) |
| Datensatznummer |
250111495
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| Publikation (Nr.) |
 EGU/EGU2015-11624.pdf |
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| Zusammenfassung |
| Introduction: The Kaali Impact Crater on the island of Saaremaa, Estonia (58.37Ë N, 22.67Ë
E) is part of a crater-strewn-field consisting of nine identified craters, ranging in size from
110m (Kaali Main) to a few meters in diameter [1-3]. The strewn field was formed by the
breakup of an IAB iron meteorite during atmospheric entry [4]. The main crater is due to its
size an important crater to study the effects of small asteroidal impacts on terrestrial
planets.
Despite some anthropomorphic changes, the crater is well preserved. During a scientific
expedition in August 2014, we mapped the crater in unprecedented detail using 3D laser
scanning tools and made detailed strike and dip measurements of all outcrops. Additional
measurements using ground-penetrating radar and electro-resistivity tomography we also
conducted to further refine the subsurface crater morphology.
The results include a high resolution topographic map of the crater, previously
unreported observations of overturned ejecta, and refined morphometric estimates of the
crater. Additionally, research conducted as part of the expedition has provided a
new, best-estimate for the formation of the crater (3200a +/- 30 BP) based on 14C
AMS dating of charcoal from within the ejecta blanket [Losiak et al., 2015, this
conference].
Structural Mapping: Although Kaali Main has been the subject of previous
investigation (e.g. [2,5,6]), most of the structural descriptions of the crater pre-date modern
crater investigations. Strongly inclined blocks were previously considered being affected by
erosion and slope processes, our new observations show that most high dip-angle features fit
well with overall dip-angle systematics. The existence of the overturned flap can be
demonstrated in at least four areas around the crater.
3D Laser Scanning: A point cloud containing 16 million data points was created using
43 individual scans from a tripod mounted Faro 3D 330x laser scanner. Scans were processed
using Trimble Realworks software. A DEM, Hillshade, Slope Map and Contour Map were
created in ESRI ArcScene software.
Photogrammetry: Photogrammetric techniques from images of key outcrops were
used to create texture, photorealistic 3D representations using Agisoft PhotoScan
software.
Acknowledgements: We extend our sincerest gratitude to the Estonian National Heritage
Board for permission to dig and make measurements at the crater.
References: [1] I.Kolkun (1922) Üldine geologia. Tallin, 170. [2] J. A.Reinwald (1933)
Publications of the Geological Institution of the University of Tartu, 30:1-20. [3]
J.A.Reinwald (1928) thesis; Univ of Tartu [4] L.J.Spencer (1938) Miner. Mag., 25:75-80. [5]
A.Aaloe (1959) ENSV TA Geoloogia Instituudi Uurimused, 2:105-117. [6] A.Raukas et al.
(2002) Impact Studies 2005, 341-355. |
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