= Ae 
. Beaches: ‘Sandbar's and Dunes_ 
Materials derived from erosion along the coast have been dis- 
tributed by waves and currents to produce fine beaches and sandbars, 
especially along the southern and. eastern sides of the Cape. Currents 
moving patallel to the coast along the south shore built bars across 
many of the bays,. improving them as harbors .for small boats by af- 
fording protection from the open waters of the Sounds, and -straight- 
ened the actual shoreline by thus reducing its irregularities. A 
similar process occurred on the north shore. in the vicinity of Well- 
fleet, Monomoy Point and. many other similar coastal features are 
sandbars piled even above the high-tide mark by the waves: and cur- 
rents. As each” new bar jutting out. from the.-coast is built,it 
protects certain parts of the coast from direct attack and causes 
further deposition of sand at some: places; . but it may also deflect 
currents and cause more vigorous erosion elsewhere. ©The broad hook 
on which Provincetown is located at, the tip. ofthe eastern arm of 
the Cape has been built up since the. ‘Ice: Age by sand arta le there 
from the cliffs. to the south. 
“Wherever the beaches are wide ences — expose - os Gene ies 
of loose sand to the sweep of the wind, dunes have been formed. The 
largest and most extensive of ‘these are, of course, those near. Prov- 
incetown and Barnstable, but along many stretches of the coast there 
are patches of windblown sand lying against the cliffs on the inner 
margin of the beaches. 
Changes in the Surface Zones~': 
The upper few feet of till and gravel deposits have been altered 
by several agencies since the retreat of the ice sheets, Frost has 
heaved and overturned some of the stones. .Roots: have penetrated be- 
tween them and shifted them. In. the. upper two or three. feet at any 
exposure, all signs of original layering in outwash materials have 
been destroyed. The topmost six inches toa foot generally. consists 
of. chocolate brown to black, sandy. soil, rich in plant remains. Be- 
neath this is a reddish-brown zone in which the subsurface materials 
have been stained with iron rust. that comes from decay of iron-bear- 
ing minerals in .the soil and is spread . by the. downward percolation 
of rain water through the ground. Generally the lower part of the 
rusty zone grades*downward into a lighter colored zone, of yellowish 
brown or'tan color. Thus, the bottom of this stained zone is very 
irregular, and its contact with unstained materials below is common- 
ly. rather indistinct. The rusty stain locally penetrates to deeper 
levels in more porous materials or along irregular cracks. Commonly 
it is hard to tell at any single roadcut or pit just how much of the 
upper disturbed and weathered material was churned up and altered in 
place, and how much material has been brought there and deposited as 
& ‘thin: top mantle by slope wash and creep from adjacent hills. Re=- 
.gardless of its origin, | however, the thinness of the zone of dis- 
turbed material corroborates the conclusion that not a great deal of 
time has elapsed sinte the ice disappeared from this region. 
