Kummakivi, the “Odd Stone” in Ruokolahti, southeastern Finland, looks improbable: a huge irregular boulder rests on a rounded bedrock rise, with daylight beneath much of its overhang. Photographs make the supporting area seem inadequate for the mass above it. The feature is real, but the geological interpretation is an ordinary glacial erratic. Its appearance invites questions about how it arrived, how much it weighs and how confidently those questions have been answered.
The most useful distinction is between an explained origin and uncertain numerical estimates. Saimaa Geopark identifies a boulder deposited by the continental ice sheet. That classification does not require every widely repeated weight or age figure to be exact. In fact, the official information provides a markedly different mass estimate from the familiar claim of 500 tonnes.
The rock and its support
Saimaa Geopark’s site description gives approximate dimensions of seven by four by five metres and a contact area of about half a square metre. It identifies the support as a roche moutonnée, a bedrock form shaped by glacial erosion. The narrow contact is therefore between a transported block and a natural rock surface, rather than a deliberately built pedestal.
A photograph is useful for recognising the boulder and its arrangement, but perspective alone cannot measure the complete contact area, the shape beneath an overhang or the distribution of mass inside an irregular block. A convincing assessment should distinguish those visual impressions from the dimensions and interpretation supplied by the geological source.
How the ice placed it
The Geopark’s geological information sign explains how freezing water can detach blocks from fractured bedrock and how moving ice transports them. As ice melts, its load can be left on the landscape. Kummakivi and its supporting rock are described as mixed granite–cordierite–mica gneiss typical of the area. Grooves and chatter marks on the support record glacial abrasion.
The sign places the emergence of this area from beneath the ice at about 11,500 years ago. It describes a former ice-lake shore around the boulder, a very different setting from today’s forest. This is an approximate account of landscape development. It is not a precise calendar date for the instant when the block acquired its present contact with the support, nor is it the geological age of the rock itself.
In Petri Kivimäki’s 13 August 2017 Yle report, geologist Aimo Kejonen, formerly of the Geological Survey of Finland, likewise explains deposition from melting ice about 11,000–12,000 years ago. He acknowledges that the common rock type prevents identification of a unique original source.
182 tonnes and the familiar 500-tonne figure
The longer official Kummakivi sign package, page 1, supplies an explicit calculation. Taking the boulder’s volume as approximately 65 cubic metres and the rock’s average density as 2,800 kilograms per cubic metre gives a mass of about 182 tonnes: 65 × 2,800 = 182,000 kilograms. The result depends on an estimated volume and an adopted density. It is not presented as a weighing operation.
Yle’s 2017 article records a different estimate, about 500 tonnes, attributed to local guide Esko Piiparinen. The two figures should remain attached to their sources. The official calculation provides an intelligible basis for its estimate, whereas the reviewed interview does not supply the measurements or calculation behind 500 tonnes. Neither number should be promoted into an exact experimentally measured mass.
Multiplying the maximum length, width and height would calculate the volume of a rectangular box around the block. An irregular boulder does not fill that box. This explains why a list of three overall dimensions is not by itself enough to establish mass. A better volume survey could refine the estimate without changing the identification of Kummakivi as a glacial erratic.
What its balance does and does not establish
A large overhang can make a rock look less stable than it is. Whether an object tips depends on the arrangement of its mass and support, rather than the overhang’s appearance alone. That is a general mechanical principle, not a site-specific stability test performed for this article. No engineering assessment or experiment to move Kummakivi has been reviewed here.
It would therefore be misleading to describe the boulder as defying gravity. Equally, its longevity should not be turned into a guarantee that every part of the site is safe to climb or disturb. The geological explanation concerns its transport and placement. Current conservation rules govern how visitors should treat it.
Curiosity, conservation and present access
The 2017 interview includes Piiparinen’s recollection of earlier visitors and a local explanation connecting the name with sounds from the supporting rock. It also describes surface damage associated with people striking that rock. These are attributed recollections and observations; they are not evidence that the block is hollow throughout or that sound caused its placement. The historical report is not a recommendation to repeat the striking.
The Geopark’s visitor sign records protection as a natural monument in 1962 and prohibits damage or defacement. It describes an approximately half-kilometre path from the Kummakivenmäki parking area, with wet ground possible. The current Geopark page continues to present Kummakivi as a visitor destination. Follow the designated approach and current signs, leave the rock undisturbed and do not climb it.
Assessment and map
The case is classified as Closed (Explained): the unusual feature is a documented glacial erratic resting on glacially shaped bedrock. The reviewed geological interpretation accounts for its origin without a supernatural cause. The discrepancy in mass estimates remains a separate measurement question; it does not make the boulder’s natural identity disputed. No specific local giant, spirit or ancient ritual tradition is asserted here without a checked source.
The map uses a rounded Geopark destination reference at 61.4933, 28.4300, based on the coordinates published on its current site page. It represents the Kummakivi area rather than the exact contact patch, a survey station or a parking bay. The boulder’s deposition is prehistoric; no modern incident year is assigned. The 1962 protection decision, the 2017 interview and later information-sign publication are records about the feature, not dates when the natural phenomenon occurred.
Sources and further reading
The primary interpretive material reviewed includes the one-page geological sign, the geology and visitor-access pages of the four-page sign package, and the current site description. The first page’s photograph, geological map and mass calculation were also visually checked. Yle’s original interview supplies the named local and geological perspectives. These sources have different purposes and should not be treated as independent measurements of every repeated number.
For another Finnish landscape with a different kind of reported phenomenon, see Paasselkä in the Cases directory. A natural explanation of one feature does not determine the assessment of a separate case.
Visit Kummakivi erratic boulder
Saimaa Geopark publishes an approximately 0.5 km designated approach from Kummakivenmäki parking. Wet terrain is possible. Follow current signs, do not climb or damage the protected natural monument, and leave the rock undisturbed.
Official visitor information → · Access information checked 2026-11-13. Check current opening and booking details before travelling.
Share an experience here →Experiences at Kummakivi erratic boulder
First-person accounts shared by visitors and reviewed before publication. They are separate from the researched case above.
No visitor reports have been published here yet.