Juniata sentinel and Republican. [volume] (Mifflintown, Juniata County, Pa.) 1873-1955, 1880-12-15
The Post Glacial History OF the Peninsula

The geological history Of the site Of
Boston, Mass. since the glacial epoch
is described as follows by Professor
Shaler, in the history of the city called |
out by the 25th anniversary of its set
tlement- After the ice had lain for an |
unknown period over this region,
elimatal changes caused it TO shrink
away slowly, and by stages, until II
disappeared altogether. As IL disap-
peared il left very deep mass oil
waste, which was distributed IN an IT.
regular way over the surface, at some |
places much deeper than at others. AT |
many points this depth exceeded 100
feet. AS the surface of the land lay |
over 100 feet below the present level |
in the district of Massachusetts Bay
when the sea began TO leave the shore,
the sea had free access to this incoher-
ent mass of debrfs, and began rapidly
20 wash 1t away. We can still see
part of this work of destruction OF the
glacial beds in the marine erosion
going on about the islands and head
lands in the harbor and bay. The
same sort of WORK went on about the
glacial beds, al the height of l0c feet
or more above the present tide line.
During this period of re-elevation, the
greater part of the drift deposits of the
region about Boston WAS worked over
by the water. Where the gravel hap.
pened TO lie upon ridge of rock that
formed, as it were, a pedestal for it, 1t
generally remained as an island above
the surface of the water. As the land
seems TO have risen pretty rapidly
when the ice burden was taken off,
probably on account OF this very re-
lief from Its load, the sea did not have
time 10 sweep away the whole OF these
islands of glacial waste. Many of
them survive in the form of low, SYM
metrIcal bow-saaped hills. Parker's
Hill, Corey's Hill, AspinwalI, Id the
other hills on the south side of Charles
River, PowderhOrn. and other hills in
Chelsea and Winthrop, are conspicu-
ously beautiful specimens of this struc-
ture. OF this nature were also the
three hills that occupied the peninsula
of Boston, known as Sentry or Beacon,
Fort, and Copp's Hills. Whenever an
open cut is driven throug these hills,
We lind in the center a solid mass of
pebbles and clay, all confusedly inter-
mingled, without any distinct trace of
bedding. This mass, termed by geolo-
gists till or bowlder clay, is the waste
Of the glacier, lying jus. where it
dropped when the ice in which IL was
bedded ceased TO move, and melted on
the ground where it lay. All around
these hills, with their central core of
till, there are sheets OF sand, clay, and
gravel, which have been washed from
the original mass, and worked over by
the tides and rivers. This reworked
bOwlder clay constitutes by far the
larger part of The dry lowlasd surface
about Boston; all the fat lands above
the level of the swamps which lay
about the base of the three principal |
hills of old BOston-lands on which the |
town first grew-were composed of the |
5edded sands and gravel derived from |
the waste of the old bowlder clay.
These terraces of sand and gravel from |
the reassOrted bowlder clay made up
by far the greater part Of the low-lying
arabic lands of Eastern Massachusetts;
and of this nature are about all the
lands first used for town sites and till
age by the colonists-notwithst
the soil they afford is not as rich nor
as enduring as the soils upon the bowl
der clag. The reason these terrace
deposits where the most sought for
towns site and cultivation is that they
were the only tracts of land above the
level OF the swamps that were free
from large powders. Over all the un-
changed drift these large bowlders
were originally so abundant that Il
was very lab0riOus work to clear the
land for cultivation; but on these ter
races OF stratified drift there were
never powders enough to render them
diff cult OF cultivation The result was
that the first colonists sought this class
of lands. One OF the advantages of the
neighborhOod of Boston was the large |
area Of these terrace deposits found
there. There was an area of - 900 or
20, 900 acres within seven or eight miles
of the town that could have been
quickly brought under the plow, and
which was very extensively cultivated
before the bowlder-coveredh hills began
10 be Tiled.