Great Lakes Origin by Diastrophic Processes

Trends of Current Flow

Trends in current flow direction in the Great Lakes region show the influence of tectonics, and effects of the earth's rotation. Along the boundary of the Canadian Shield, sedimentary formations tilt upwards, indicating uplift. The uplift was greater in northeastern regions.

If the uplift occurred when the region was submerged, it would spill waters towards other areas, and initiate currents. Southward flowing currents would tend to be deflected to the west because of the earth's rotation, due to the principle of conservation of angular momentum. A north flowing stream would deflect to the east, for the same reason. This phenomenon is responsible for the Coriolis force which affects the rotation of hurricanes, and causes the Gulf Stream to flow eastward across the Atlantic. The earth's rotation is believed to influence the manner in which large rivers flowing north or south erode their banks, an effect known as the Baer-Babinet Law [Fairbridge, 1968, p. 49].

Any mass of water on the earth would have an angular momentum about the earth's axis of rotation. If a southward current was generated by crustal uplift in the Canadian Shield, the conservation of angular momentum of the displaced water would cause the south moving current to drag on the earth's rotation. This deflection of the current towards the west, because of the inertia of the displaced water, would erode and streamline the earth’s surface below, and the friction would tend to accelerate the displaced flood water.

The erosional features and streamlined landforms in the Great Lakes region show a southeasterly current trend. Deflection of currents from the north due to the earth's rotation could explain the dominant southwesterly trend of these erosional rock basins and streamline features. As floodwater flowed south, its erosional power may have increased, because of its inertia in a faster moving environment. Patterns of drumlins in many parts of the Great Lakes region indicate the trend of the current flow was towards the southwest. The chain of lakes along the perimeter of the Shield, where Paleozoic sediments overlying the Shield were eroded away, shows the scale of the currents.

Differential erosion was a factor in the excavation of the Great Lake basins; the currents eroded the softer shales and muds to relatively greater depths, while resistant rocks such as dolomite and limestone remained intact, forming headlands, and great escarpments such as the Niagara Escarpment.

Current velocities in the immediate vicinity of the uplifts would be limited, but the erosive power of currents generated by an uplift would vary with the area. For a given area of uplift, the maximum velocity tends to occur at the perimeter.

References

Fairbridge, R.W., 1968. The Encyclopedia of Geomorphology. Reinhold Book Corp., New York..

Related Sites

The Coriolis Force


© 1999 by Douglas E. Cox
The Creation Concept