Wilson suggested that the Sierra de Santa Cruz moved to its present position by gravity sliding. The writer agrees and some years ago developed a hypothesis to explain how this mass of ultramafic rock might have been uplifted to a position from which it subsequently could slide northward.

The Sierra is about 55 km long by 13 km wide, rises to an elevation of about 1,000 m, and is composed mainly of peridotite, gabbro, and dunite. Airborne magnetometer surveys have indicated that beneath the east end the depth to crystalline basement is 4,000-5,000 m.

It is postulated that the uplift of the Sierra de las Minas, from which the Sierra de Santa Cruz is presumed to have moved by gravity sliding, may be analogous to the Troodos massif on the island of Cyprus; i.e., the arcuate band of ultramafic rocks across Guatemala was underthrust by a southward movement of the Yucatan platform and the resulting isostatic uplift raised a mass of peridotite to a height from which it could slide northward to form the Sierra de Santa Cruz.