[Mooring Holes in] "Some Points of Controversy"


About forty rock drillings termed 'mooring holes' have been reported from the Great Lakes region, chiefly Minnesota; there are a couple from the Cape Cod and Long Island Sound area. The holes occur in boulders strewn along present or past waterways. Generally, they measure about one inch in diameter and are between five and seven inches deep. Many are triangular. The theory is that ancient Norse ship crews drilled such a hole whenever they needed temporary mooring and assurance of a quick get-away. The hole was said to be intended for the insertion of a hawser pin of iron or wood, tight enough to hold the ship securely, but loose enough to allow the line to be flipped loose instantly when danger threatened. Thus the occurrence of such holes supposedly indicates routes travelled by Norse naval expeditions.

Aside from the fact that such a method would be cumbersome and unreliable (it would necessitate nightly drilling in rocks, and changes in temperature and humidity could affect the fit of the pin), the method is unknown in Norse seamanship, medieval or modern. In fact, the entire concept of'mooring holes' is built on a misunderstanding.


The theory was developed by Hjalmar Holand after he observed Norwegian fishermen tying their boats to iron rings fastened in boulders and cliffs on the shore. These were permanently installed ring bolts, however, needed wherever ships sought port repeatedly. Such ring bolts are known the world over and are quite common in twentieth-century America.

Temporary mooring, on the other hand, is another matter. In Scandinavia, as in most other parts of the world, the procedure involves nothing more elaborate than a line thrown around a tree or a stone. If security was a factor, the ship simply anchored at a safe distance from the shore.

Other stones with identical drillings in the immediate vicinity of the 'mooring holes' provide a clue as to what they really are: they are blasting holes drilled by the early settlers to split stone for foundations, and no hole has been proved to be older than 1860. Many of the stones were never dynamited for one reason or another. The holes are triangular because they were drilled with a hand-held, dull or straight-edged drill bit which invariably produces a triangular hole. On the farms in nineteenth-century Minnesota blasting holes were commonly drilled with regular one-inch bits, hence the one-inch diameter of the holes. The 'mooring holes' are indeed in more aspects than one the most unbelievable archaeological evidence ever presented for Norse penetration into the American continent.

Blast Hole at Sinking Lake, Minnesota

Mooring Holes and Chisels

Source: Birgitta L. Wallace, "[Mooring holes in] Some Points of Controversy" in The Quest for America, Geoffrey Ashe (New York: Praeger, 1971), 155-174.

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