One of my personal research projects is looking for
circular features, using Google Earth. I mapped
more than a thousand circulars in Mexico: Sonora, Baja California, Sinaloa, and
Chihuahua. One very
strong pattern stood out, a chain of circular features extending more than 300
miles. In order to
emphasize this feature, only circular features belonging to the chain are shown
in the view below.
More than 100 circular features delineate this feature.
closer view of outlined circular features
Without mapping the circular features, there is no
visible evidence from this height of a
unmarked view of the area
This was was obtained by rotating the feature clockwise
in order to emphasize the linear nature and
scale. The original trend of the line is N58W.
Fresh, easily identifiable volcanic features are found
at the northeast end of the line, indicating that
this is the youngest segment of the linear feature. This observation tends
to support the idea that the
linear feature started in the southwest and slowly migrated to the northeast,
leaving behind weathered
volcanoes and intrusions.
Easily identified maar volcanic features, only slightly
weathered are also found near the northeast
end of the line of circular features.
Color can also be used to emphasize the linear feature.
Color refers to strong red, orange, and yellow
colors of oxidized iron minerals present in volcanic materials. The
concentration of strong iron oxides
colors predominate near the southwest end of the chain. This is reasonable
if the source of the hotspot
trail moved from southwest to northeast. The southwest end of the chain is
older and has experienced
more weathering. The color cluster at the northeast end of the chain are
small basaltic volcanoes that
have weathered quickly.
an oblique view of the cluster of volcanoes at the northeast end of the linear
chain of circular features
a closer view of the distribution of volcanoes at the northeast end of the chain
an oblique view of the linear chain from the southwest end
Just credit photos to Google Earth/R.Weller/Cochise College.