Streamlined Rocks

On the Summit of Silver Peak

Streamlined rock on Silver Peak
Streamlined quartzite near the summit of Silver Peak, in Killarney Provincial Park, Ontario.

Detail of streamlined quartzite
The photo shows details of the streamlined quartzite near the summit of Silver Peak, about 360 m above the water level of Georgian Bay. The features resemble streamlined rocks that occur along the shore of Georgian Bay.  Note that striations are parallel to the streamlining.

Streamlining in granite

Streamlined rocks in Killarney Provincial Park
Streamlined rocks in Killarney Provincial Park, seen from the turn-off road to Bell Lake. Undercut channels carved in steep rock faces are called cavettos, and are attributed to vortices that impinged on the rock in the streamlining environment. Current flow was towards the southwest, left in the photo.

Streamlined rocks at Collins Inlet
Streamlined granite rocks along the shore of Georgian Bay, at the Western Entrance of Collins Inlet.

Erratic boulder transported by currents

Boulder of quartzite on granite
The photo shows a boulder of quartzite on granite bedrock at the location from which the previous photo was taken, the Western Entrance to Collins Inlet near the shore of Georgian Bay. In this area, most of the boulders and pebbles smaller than 0.3 m have been swept away by the powerful currents that caused streamlining of granite and quartzite. This boulder appears to have been transported by the currents from the La Cloche Mountains several km northeast of the site.

Plot of clast diameter vs KE
Variation of kinetic energy with clast diameter for clasts with velocity 10 m/sec. The estimated velocity of currents in the cataclysmic floods at the nearby French River was between 4 and 15 m/sec, according to Kor et al (p. 640). In contrast, the kinetic energy of clasts at the base of an ice sheet would be negligible because of the extreme slowness of ice motion.

Kor, P.S.G., Shaw, J., and Sharpe, D.R., 1991. Erosion of bedrock by subglacial meltwater, Georgian Bay, Ontario: a regional view. Canadian Journal of Earth Sciences, 28: 623-642.

Cycle of uplift, erosion, disintegration

Cycle of uplift, erosion, disintegration
The graphic above illustrates the cycle of uplift during former catastrophic conditions. Uplift of submerged areas generated fast currents, which caused erosion, and removed sedimentary overburden. Streamlining of rocks is evidence of erosion by those fast currrents. Unloading initiated disintegration, and formation of drift, which may have promoted more erosion, as disintegrated materials were more easily eroded. Currents transported the sediments far from the eroded areas and redeposited them. The isostatic consequences of enhanced erosion completed the cycle, resulting in further uplift. This cycle of uplift, erosion, and disintegration could result in rock basins, such as those occupied by the Great Lakes.


Pothole at George Lake
A Human Figure in Quartzite
Drumlins in Lake Ontario

Copyright © 2003 by Douglas Cox