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Transactions of the Symposium on Photo Interpretation

Soil formed from
décalcification of till
Ridge of till,
troughs of sandy soil
Chalky till
Chalk in situ
Fig. 3. Contortions in Chalky Till, Garboldisham, Norfolk
of heather (Calluna vulgaris) and grassland (dominated by Agrostis and Festuca
spp.). Subsequent work has now shown that in the latter case the heather was
rooted mainly in the deep, acid, sandy soil in the troughs while the grasses
were growing over the chalk-rich ridges. Careful field examination has reveal
ed many other cases where the vegetational differences were less spectacular
but still easily mapped.
Since 1946, aerial photography, both vertical and oblique, has shown that
the patterns are far more numerous and widespread than was at first suspected.
Patterns of slight differences in soil colour, subtle changes in vegetation and
small differences in crop performance, none of which are easily seen on the
ground, are often readily identified. Exceptionally, patterns have even been
detected by variation in the rate of melting of a thin cover of snow.