At last count, only 10 structures in Eastern Canada
have been verified as meteorite impact structures.
During the past 6 years, I have spent hundreds of hours
examining Eastern Canada in close detail
using Google Earth. So far I have identified nearly 2500 circular
features. I have cataloged the features,
measured their diameters, and outlined the structures. At the scale shown
in the following view, it is
almost impossible to see the circular structures whose diameters are less than 2
kilometers. For reference,
the Arizona Meteor Crater is a little more than one kilometer in diameter.
Here is a closer view of the northern section of
Eastern Canada, showing the abundance of smaller
The southern portion of the area also has a nearly
random array of circular features. Near the bottom
of the following view there is a concentrated chain of circular features with a
southeast trend. I am not
proposing that all of these circular features are meteorite impacts. It is
very likely that there many other
geological phenomena that can produce these circular structures: mantle plumes,
contact metamorphism, ring dikes, volcanoes, and circular fold patterns in
metamorphic fold belts.
Amongst these thousands of circles, many might be the remains of deeply eroded
craters. The features can only be verified by exploration on the ground.
Eastern Canada is a unique feature on Earth. The
Canadian Shield surface was ground down by
intense glaciation while this area was part of Rodinia. During the last
recent glacial ice age the land
was then scraped clean by glaciers moving across the area. This glacial
planing is analogous to running
a piece of rough wood through a planer and exposing the knots. Even the
scratches left on the planed
board correspond to glacial striations created by continental glaciation during
the last ice age.
map of thousands of glacial striations left by the Wisconsin glaciation
Although the glaciers cleared away much of the surface
material in Eastern Canada, other types of
structures emerged, fractures and striations from earlier glacial motions.
In order to pick out circular
features from the complex patterns, the fractures and earlier glaciations had to
be mapped. This also
required mapping of more than 10,000 linear features. These linears were
mapped using the measuring
tool that accompanies Google Earth.
Here is a closer view of the northern portion of
Eastern Canada, showing the complexity of fracturing.
The map is incomplete. If all linear features were to be mapped, the map
would be solid pink (and my
computer would probably crash). Only the longest features were recorded.
Even at this level, some large
circular features start to appear.
Here is a somewhat closer view of the linear features. Notice the
two dark areas to the upper left of the
center of this view. These are the Clearwater Lake West and Clearwater
Lake East, both large meteorite
Here is an unmarked closer view of the two Clearwater
Lakes impact structures. The area is dominated
by glacial striations.
However, when the glacial striations are ignored and
only the random-oriented linears are plotted,
a dense ring of random linears outlines each of the impact structures.
This is somewhat surprising because
one would expect to find an abundance of concentric and radial fractures from
such large explosions.
Radial and concentric linears are almost non-existent. I have also applied
my mapping techniques to a
meteorite impact structure on Victoria Island in Canada and I have seen a
similar ring of random fractures
around the impact structure.
I am including a collection of examples of the types of circular features
that I have mapped. These
circular structures are subtle, otherwise that would have been mapped long ago.
As the resolution of
Google Earth views has improved over the years, many more circular features were
glacial striations, deposition of sediments, and dense plant cover still obscure
many of these features.
Even if many of the features are of igneous origin, the
might be useful for mineral exploration.
There might be a complicating factor; deep erosion may have removed the original
I suspect that there are still hundreds of these that I
have not yet mapped. This presentation is really
just a progress report.
Examples of Mapped Circular
Features in Eastern Canada
(a small portion of the
mapped 2500 circular features) example 1- Manicouagan
impact feature example 2- #3237 diameters 3.5 km / 13.7 km example 3- #16-087 diameter 5.2 km example 4- #16-054 diameter 16.5 km example 5- #16-060 diameters (left) 10.9 km, (right) 3.4 km /
8.5 km example 6- #16-176 diameter 165 km example 7- #16-004 diameters 0.54 km / 0.81 km example 8- #16-122 diameter 3.9 km example 9- #16B-124 diameter 6.1 km example 10- #C0889 diameters 0.6 km / 1.9 km example 11- #16B-151 diameter 3.3 km example 12- #16-052 diameters 21.7 km / 76.1 km
Just credit photos to Google Earth/R.Weller/Cochise College.