Evening star., 1937-06-10
STARS, MEN AND ATOMS
Notebook of Science Progress in Field,
Laboratory and Study.
BY THOMAS r. HENRY,

Seemingly etched on the surfaces OF
hard sandstone rocks through the arid
Southwest are what appear to be figures
of gigantic SunfoWers.
These long have been objects Of rev.
erence to the Indians as actual lnslgnlas
of the sun itself They have been a
complete puzzle to archeologists. Per-
haps the most notable of them was dis
covered more than 20 years ago by the
late DR.. J. Walter Fewkes, Smithsonian
Institution archeologist, in excavations
of the celebrated cliff dwellings at what
is now Mesa Verde National Park, in
Colorado. 1t was part Of structure
evidently erected as temple for worship
Of the sun.
The geological puzzle at last has been
solved by Walter B. Lang. Geological
Survey geologist, working with a specl-
men now in the Smithsonian Institution
collections. In a sense the old clln
dwellers were right. The sun actually
did etch it's own image in the hard rocks
through the processes of erosion.
These giant sunflowers at Mesa Verde,
considered typical of all the others.
usually range from one to two feet IN
diameter. They are composed OF two
parts, a central bowl from one to six
inches deep and fringe OF radiating
ridges or burrows surrounding the bowl.
Near the margin of the bowl the ridges
and burrows bend sharply downward at
an angle whose steepness depends on
the depth of the bowl. The figures are
usually Enthusiastically circular.
Now, the geologist points out, sand
stone may be considered as made up of
tiny particles of quartz cemented to-
gether with silica, combined with various
other materials, such as calcium car
Donate and hydrous iron oxide. The de-
gree Of cementing is not the same for all
parts of a rock. Rain water falling on
the surface, containing small amounts
of carbonic and various organic acids.
tends to dissolve the binding cement and
set free the tiny grains Of quartz, which
may be blown away by the wind.
The natural tendency is to form pits
in the surface OF the rock, where the
cementing material is least resistant to
this process. In a moist climate that is
about all that happens. The "pitting"
develops very slowly and seldom in a
definite pattern. The water tends to
sink through the rock to the natural
water table. Quite different is the situa-
ton in the arid Southwest. There most
of the rainfall is in the form of brief,
heavy showers. The air is dry. The
porous surface rocks quickly become sat-
urated, but dry out rapidly after storm
has passed. Most of the moisture in
the upper part of the rock Is drawn to
the surface by capillary action or by
plants and is evaporated.
Dissolved in this water as 1t IS drawn
to the surface are various mineral salts.
Where parts of the rock protrude Slight
ly above the general level more OF these
salts are deposited, tending to restrain
erosion in those areas. The lower areas
accumulate more water, suffer more
solution and acquire less salts. Thus
what may have been tiny depression
tends to develop into deep pocket in
a relatively short time. Such pockets
are the disks of the giant sunfloWers.
AS depression forms it becomes a
center for accumulation Of rain water.
Rills develop upon the rim, extending
outward as they conduct more and more
water toward the central basin, and
deepen to form radial troughs. II the
depression deepens rapidly the radial
lines and troughs follow down into the
basin as well as grow further outward.
It Is these which constitute the rays, or
petals, OF the sunflowers.
So, says Mr.. Lang. "the Sun Symbol
mark Is q transient impression made
upon the weather1ng surface m rock and