MICROFORMS AND FEATURES
tive cover. Considering the magnitude of
these features, it can be seen that several fac-
tors would blend into one form because often
one, such as drainage, is the result of another,
such as relief. It follows too, that with a given
drainage situation the conditions of weather-
ing are established, soil forms, plants grow,
and organic matter develops in harmony with
this localized environment. The resulting
composite effect is a micro-feature.
Broad airphoto identification of land forms
is elementary. For example, water and land
can be separated without effort or thought.
Alluvial plains, mountains and hills can also
be distinguished by topography alone.
A second stage of classification may be con-
sidered as separating consolidated and un-
consolidated materials. This would entail
mapping out glacial deposits, aeolian mate-
rials, and water-laid materials and separating
them from the bedrock areas. This stage will
require more care, some thought, and a degree
of skill.
In the third classification, more skill and
experience will separate water-laid materials
into flood plains, coastal plains, lacustrine
materials, low terraces, and outwash plains.
Similarly, glacial deposits can be divided into
till plains, moraines, kames, eskers, and drum-
lins; aeolian, into loess and dunes. The vari-
ous bedrocks can be subdivided into general
classes such as sedimentary, igneous, meta-
morphic, or perhaps ''complex."
All of these may be identified by the recog-
nition of characteristic features of gross mag-
nitude. These were first organized and pre-
sented in 1939! and 1945.? Under this system
refinements were incorporated that tied some
unique micro-features directly to certain
types of rock and soil. Thus the widely recog-
nized *'pitted plain" typified a feature associ-
ated with soluable limestone, gypsum beds,
and a few ancient calcareous gravel deposits.
As early as 1949, "infiltration basins," in-
distinguishable on the ground, became a dis-
tinctive criteria for gravel identification as
separate from predominately sand deposits.
At the same time, the grooves in lake-bed
sediments made by pan ice were related to
shallow water conditions of the pleistocene
lakes, and thus to the more salty soils. With
these and other rough tools the sands, gravels,
silts, and clays and some soil combinations
could be identified. Likewise, clay shales,
sand shales, sandstones, siltstones and lime-
! The Engineering Significance of Soil Patterns,
Highway Research Board Proceedings.
2 The Formation, Distribution and Airphoto Iden-
tification of U. S. Soils.
6
stones among the sediments; and granites,
lava, and gneiss (undifferentiated) were
identified by criteria then available in air pho-
tos by these analytical methods.
Between 1949 and 1952, distinctive fea-
tures of schist, slate, serpentine, rhyolite and
basalt, all largely in the macro-feature class,
were reported? and, currently, improvements
in the art have progressed to the point that
injection gneiss, quartzite, gabbro, tuff, dio-
rite, andesite, phylite schist, and quartzite
schist, have been and are being mapped in
reasonably favorable circumstances.
Naturally the optimum areas for this work
are to be found in high altitudes, dry climates,
or in the glacially stripped areas of Canada.
Despite the concern held for the screening of
such features by vegetative cover, they have
been applied successfully in tropical rain for-
est areas such as Surinam, Burma,* and the
Philippine Republic.
The purpose of utilizing micro-features of
all types is to achieve greater refinement in
mapping and in the location of ore bodies. It
further reduces, simplifies, and permits in-
telligent direction of field geology and drilling
programs.
In a large sense, micro-features belong to a
new association of old geologic ideas and
principles that have been made possible by
the advent of aerial photography. Now that
air photography has been accepted for pur-
poses other than topographic mapping, the
way is open to a new era of applied or directed
photography. To consider the progress al-
ready made by utilizing an average scale of
1:20,000 on conventional film by production
laboratory processing procedures, makes the
era of special photography a welcome one.
Such an improvement can be likened to the
conversion from the stone axe to the hydro-
gen bomb in the field of warfare.
Two important points are available for
philosophical consideration. One is that this
is one of the few “open-end’’ sciences remain-
ing. It is unusual to find a field in which no
valid limitations have been established. It is
a field of infinite possibilities in which little
progress has been made. No one has thor-
oughly investigated this field so that they
might say, “These are the defined limits; be-
yond this point further effort is useless.” The
3 Airphoto Analysis of Landforms, 1951. Au-
thored by myself and Cornell University technical
report #3 for the Office of Naval Research. Vols. I,
General Analysis; II, Sedimentary Rocks; III,
Igneous and Metamorphic Rocks; IV, Water-laid
materials; V, Glacial Materials; VI, Wind-laid
Materials.
4 Landforms of Burma, 1955, authored by myself.
