In many beginning level geology textbooks it is briefly
mentioned that the source area for the ice sheets
that covered much of North America during tghe last age started in central
Quebec. Usually the discussion
stops there. No evidence is provided for the statement. Wouldn't be
nice to see some of the evidence.
Well, here it is, thanks to the opportunity provided by Google Earth.
area being studied
Several thousand glacial striations and
grooves were mapped in order to create this map. The
project was more complicated than what I originally anticipated. In many
areas the striations were
quite apparent, but I also had to contend with 11,000 years of erosion,
overlapping sets of glacial
striations from earlier advances, exposed folded rock layers, and random faults
overall view of the glaciated area
In order to grasp the full significance of the size of
this feature, you need a map scale.
region of prevalent glacial striations
A closer view of the southern portion of the
glaciated area shows the large number of lines needed to
delineate the glacial striations. These lines were generated by using the
measuring tool that accompanies
closer view of the southern portion
closer view of the western portion
closer view of the eastern portion
Mapping the northern portion of the glaciated area proved to be
problematic. In the case of
overlapping striation patterns, it was difficult to decide which one was the
most recent. Some the
the older patterns were larger and deeper than the youngest striations.
Some of the younger striations
also turned and followed the older grooves. A real problem occurred with
the exposed areas of folded
rocks. The exposed rock layers closely resembled glacial grooves.
Some of the linears in the northern
area might actually be exposed rock layers, not glacial grooves. The data
for these lines is in a kml file
that allows editing of the features, removing or adding new lines.
closer view of the northern portion
an even closer view showing the uniformity of the flow pattern of glaciation
an even closer view of what the glacial striations actually looked like
the same area as viewed above but with the glacial pattern marked with lines
an even closer view of actual glacial striations
an oblique view of a well known feature, the Clearwater Lakes meteorite impact
a final view of the complexity of glaciation plus a scale for size
Just credit photos to Google Earth/R.Weller/Cochise College.