Fig. 1. Distribution of seismically induced landforms especially near the village of Kallo.
(basic map © National Land Survey)
As the Finnish elevation model has evolved, new landforms have been revealed.
Now this happened in the Kittilä region (Fig.1). There are occurences also outside the map. I have outlined the location of mainly three main types of special landforms. I have not seen quite the same elsewhere, but of course if you know what to look for, the searcher will find it easier. Further northeast towards Saariselkä, there is a somewhat similar network in places, but polygonal and subtle, which may also be patterned during the periglacial phase without seismic influence. Northeast of Kuosku (Savukoski) there are also some similar but minor occurences as in Kittilä.
Certain deformations appear to be formed, both for relatively large formations of moraine or fluvioglacial material and also for smoother areas. The main "new landform types" are 1) grid-like surfaces, 2) fields of small spherical mounds and 3) other related landforms including minor landslides, mass flow formations, liquefaction bowls, and perhaps till or sand blows, too (Fig.2.). Without further examination and terrain research, interpretation of landforms is so far tentative.
The "1) ditches and 2) "balls" form a relative topography of up to about 2 meters height, but other related landforms in the area may be considerably bigger. The distance between the grid ditches varies and is e.g. 10-50 m. Round humps and ridges often have a width of about 15 m. Individual pattern areas are often 2-20 ha in size, but can form concentrations of more than a square kilometer. There is a lot of gradual variation in form within the patterns inside the categories and from category to another reflecting the local progress and intensity of the seismically induced process.
Fig.2. Seismo-glacial landform surfaces. 1) Grid-like 2) sphere-like. One more landform type in the picture could be seismically induced landslide or mass flow edge of the formerly mentioned categories. These processes can produce also bigger crescent and other odd forms among others.
(Hillshaded map © National Land Survey)
These are probably earthquake-induced and liquefaction-induced deformed till and sand formations (Obermaier 2009). Some of those are described also before from paleoseismically active zones in Lapland (e.g. Sutinen et al. 2018, Sutinen et al. 2019a, b): Pulju moraines, liquefaction bowls, other liquefaction-induced deformations and mass flow formations. But except for Pulju moraine and liquefaction bowls those cases do not show distinct structures and strange shapes as can be seen directly from the elevation model in Kittilä.
Seismo-glacial landforms in the area have apparently been shaped and are now visible horizontally as described vertically in the textbooks of soft-sediment deformation structures (Obermaier 2009, Fig.7.3). Of course, the development of the peculiar and diverse surface morphology in the area has been widely influenced by many seismic and other processes. There are also Pulju moraines, other seismically induced deformations, mass flow deposits, landslides, liquefaction bowls and so on, There are intensive postglacial or late glacial faults, which is the basic explanation or connection that these landform surfaces occur in the area. The area has also been intermittently an ice divide zone and therefore is not patterned very much by sharp active ice and other deglacial landforms, but the smooth surface gives a good background for seismically induced formations or numerous meltwater channels and deposits and bedrock faults to gain visibility.
Apparently, where ditches or grids are now visible, the earthquake has shaken a firmer surface layer over the liquefaction layer to form tiles or ditches. As the deformation progressed, the earth slabs were moving, shrinking, and in some places forming spheres, which may be partly sand blows. Excess material moved to the edges of the earlier hummock or a little higher plateau, forming edges and slopes that were thicker inward than outward.
Another alternative to the emergence of these geometric shapes could be periglacial processes without any seismic effect. In that case, it would be a patterned ground phenomenon. And there could be hypotheses for genesis based more on meltwater activities.
References
Obermeier, S.F., 2009. Using liquefaction-induced and other softsediment features for
paleoseismic analysis. In: McCalpin, J.P. (Ed.), Paleoseismology. International
Geophysics Series. 95. Elsevier, Amsterdam, pp. 497–564.
Sutinen, R., Hyvönen, E., Middleton, M., & Airo, M. 2018. Earthquake-induced deformations on ice-stream landforms in Kuusamo, eastern Finnish Lapland.Global and Planetary Change, Volume 160, January 2018, Pages 46-60
Sutinen, R., Andreani, L., & Middleton, M. 2019. Post-Younger Dryas fault instability and deformations on ice lineations in Finnish Lapland. Geomorphology. Volume 326, 1 February 2019, Pages 202-212.
Sutinen, R., Hyvönen, E., Liwata-Kenttälä, P., Middleton, M., Ojala, A.E., Ruskeeniemi, T., Sutinen, A., & Mattila, J. 2019. Electrical-sedimentary anisotropy of landforms adjacent to postglacial faults in Lapland. Geomorphology, Volume 326, Pages 213-224.
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