The Wolf Cave
cavern is located in an area rich in finds of geological deposits that
predate the last Ice Age. The moraine ridge that lies east of the
Susivuori, for instance, was formed during the melting phase of the
penultimate glaciation some 140 000 years ago.
itself is formed of granodiorite, which is some 1,9 billion years old.
Granodiorite typically cracks parallel to the surface, a phenomenon
which apparently explains the formation of the Wolf Cave cavern. Over
the millennia, mechanical and chemical erosion have gradually widened
the crack into a cavern. The exact size and shape of the cavern are not
yet precisely known because it was filled up to the roof by sediments.
So far, only some 80 m2 have been excavated. The maximum height of the
entrance is 1,5 m. An area of some 25 m2 located near and to the east
of the entrance is 1.8-2.2 m in height. Ten metres inwards from the
entrance the floor forms a small shelf; the height of the ceiling at
this point is 0.7 m.
In order to define
the size of the Wolf Cave cavern, a ground radar scan was performed in
the winter of 1998 from the top of the Susivuori above the cavern. The
method is based on differences in the moisture content of the rock and
the soil. According to the scan, the cavern is some 30 metres deep and
25 metres wide at the entrance. The cavern appears to be shaped like a
long triangle, and narrows down evenly from the entrance to a width of
around two metres at the back. It is difficult to define the height of
a cavern with ground radar because the upper layers of sediment are
usually dry and only the lower layers are saturated with water.
Nevertheless, it appears that the excavated space and the rock shelf
behind it are followed directly by a higher space several metres long.
Due to the effects
of various geological events, the cavern has filled up with diverse
sediments during the Quaternary Period, i.e., the last 2.6 million
years. So far, six different sediment layers have been identified in
the cavern. The topmost layer was formed during the postglacial Ancylus
Lake Period some 8000 years ago. The next two layers were formed by
older beach phases. The fourth layer is an ancient ground surface,
actually an old cavern floor, dated by thermoluminescence to over 100
000 years ago. The two deepest sand and gravel layers (V and VI) are
older yet. The most important layers from both an archaeological and a
geological point of view are layers IV and V. According to clay mineral
studies and pollen analyses, layer IV represents an old ground surface
that dates from one of the warmer interglacial periods. Layer IV
contains clear Indications of human presence, including fire-cracked
rocks. Magnetic susceptibility readings taken at the site indicate the
presence of hearths in the cavern.