Abstract:
Spectacular rock formations have developed in coarse, poorly sorted conglomerates and arkosic sandstones at Hopewell Rocks in the Bay of Fundy, which has the largest tidal range in the world. The average gradient of the shore platform is 3.2 degrees, although it varies because of slight differences in rock hardness. Schmidt Rock Test Hammer measurements show that the rock is generally no more resistant in 16 stacks and in one stack-arch than in the adjacent platform and cliff. Most stacks, arch-tunnels and caves in this area result from dissection of the rock mass along prominent, well-spaced joint planes. Old photographs suggest that the stacks at Hopewell Rocks may have developed in the :Last 100 to 250 years. Notches are ubiquitous at the cliff foot, and they are responsible for the characteristic mushroom-shaped appearance of the stacks. Although there is no consistent relationship between the depth of notches on the seaward and landward sides of the stacks, the notches are at higher elevations on the seaward side. The deepest part of most notches is a little below the mean high tidal level, although several are up to 1 or 2 m below it, especially on the landward side of stacks. Stack morphology and notch depth change in a fairly predictable manner through time, as the stacks become increasingly isolated from the cliff. (C) 1998 John Wiley & Sons, Ltd