The Search for Meteorite Impacts
                              Eastern Canada
Cochise College                                                                                        
Geology Home Page 
Geology Exploration Using Google Earth  
Roger Weller, geology instructor 
( )

original posting:  10/10/16           35 views

     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
circular features.    

     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, igneous intrusions,
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 meteorite impact
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
impact craters.

     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 discovered.  Fractures,
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 mineral deposits.

     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.