The Oskaloosa herald. (Oskaloosa, Mahaska County, Iowa) 1885-1919, 1914-02-19
MUD LUMP MYSTERIES


of each OF the mouths of the Miss
issippi is characterized by large
swellings or upheavals of tough
blush-gray clay, to which has been
applied the name mud Jumps" Many
of these mud Jumps rise just offshore
and form islands having a surface
extent of an acre or more and a
height of or 10 feet, but some do not
reach the water surface. These mud
Jumps, in addition to being of i'm,
portance because of their effects on
the channels of Mississippi river, are
also of considerable purely scientific
interest, for their development is not
included in the usual conception of
delta growth, and although several
theories have been advanced, their
cause must still be regarded as I'M
certain.
To an observer at the mouth of the
river the idea that the region is Il
great dumping ground for a large part
Cf the United States is most impress
sive. The land is being built out
into the sea at an estimated aver
age rate of about 300 feet a year; in
some places the rate is much more
rapid than in others. In one place in
Garden Island Bay the land appears
70 have advanced 1000 feet in the
spring Of 1912.
The mud humps are commonly 90 TO
30 rods broad and stand 20 or 30 feet
above the adjacent bottom. Their
growth occupies from a few hours to
several years and is usually irregular.
Generally mud lump rises in few
weeks or months ID a height of 4 or
feet above the surface of the water.
Then it remains quiet and is beaten
down by the waves in the course OF a
few years. Many of them subside,
however, and some disappear over
night. Those that rise slowly are
considerably worn before they stop
growing. while those that rise more
rapidly and in protected places are
capped by Eliminated silt having a
maximum thickness CT 10 feet.
The stories related by sailors and
pilots concerning the mode of growth
of the mud Jumps are fairly consist,
ent. One man. however, states that
the growth Ct mud lump was &C,
companied by a rather loud road as il
rose above the waJer, and another
states that he once saw flashes of
light arising from a mud lump, but
these statements are very different
from the great mass of testimony con-
corning the lump, and it seems prob.
able that they are not based on fact.
Among the most conspicuous and
impressive features of the mud
Jumps are the mud springs that are
active on many, If not all of them.
The discharge from these springs con-
sists Of salt, watery mud, and gas
in fact, gas escapes at many places
on the surface of the Delta of the
Mississippi, the vents appearing TO be
most numerous and largest on and
near the mud Jumps, though the rate
OF flow rarely, il ever, exceeds few
<ubic feet an hour Gas rises in bub-
bles in all the mud springs, though
Its rate OF issue varies.
II is considered by some scientists
that the mud Jumps are produced by
gentle seward flow of layers OF
semifuid clay under the land and the
shallow water near the ends of the
passes. The mud Jumps appear 10
be the product OF flow. because in nc
other places have such thick bodies
OF clay been found, and the fact that
they occur almost exclusively near
the ends Of the passes and that they
are most active during and ar Ell
times OF high water seem TO support
this theory.