spread over its thin margins just 
laske. But they were immigrants 
Glacial Deposits 
While the ice was accumulating in low areas and valleys, clocks 
of rock loosened from valley walls by strozg frost action rattled 
down and landed on its surface. Torrermts of reinneter washed great 
quantities of soil and stones onto it. Strong cold winds blew dust 
geross .its surface and it became dirty ice, mich like thet which 
develops some time after a snowstorm even today. This material was 
then covered with more ice and the process revestec.- At the base of 
the ice or along the side walls underneeth, loose soil, boulders,and 
blocks of rock were frozen into the srowing gieciers As it moved, 
already charged with rock debris, it scraped still more material 
from the floor and sides, and plucked. huce 21 om surfaces over 
Which it rode. Soils in front of it o ds ul 
to be overridden and incorporated, i 
: Pp ’ 
jumbled fragments in the lower part or 
oOo 
i) 
ab pet 
Le 
terial thus carried in the ice as it by 
derived from it,was destined to be dep nds 
the process or when the ice melted. in ots oc: 
or boulders that must have travelled their Source. 
During the advance, the glacially-transvori ents acted as 
abrasives to scrape and polish bedrock lean and widen 
the bottoms of valleys, or scratch s lel grooves on 
rock floors such as may be seen at th es throughout 
New Englend. In this way the debris-le and puiveruzed 
much of the materials over which it roc thet iv was car- 
ryinge Many fragments that escaped crushin ided, polished, 
and scratched by the smaller particles led among them 
or were dragged against sharp projecting s oz: hardsr rocks locked 
an, the icy grip of the glaciers ‘ 
| All along the irregular front of @ = 
a@ jumbled mass of rock materials was piled 
to forma belt that now extends i s ss the 
countryside and marks the uneven i CYANCE « t of it 
may have been shoved along like material in front of a plow,and part 
of it was merely dumped where it now ilies es the ice border nelitede 
Geologists call such a deposit of ice-borre nsterials a moraine. 
4A moraine may range from a few yards to several miles in widths 
and its hisher parts may rise a hundred feet cr more above its sur- 
roundingse At some places it may. stand om isvel ¢ 3 Grewse— 
€ 
where it may.rise along the slopes of Hil 
jAocation determined by the position of 
time of depositione 
Where the .moraine is rather wide 
Simultaneously, of course, Materiel 
later with similar material by s1i 
pushed forward to new positions. 2h 
