196 
rounding territory. Among the arctic or sub-arctic plants on 
these peaks are, for example, the Lapland Rhododendron (2. 
lapponicum), alpine willows (Salix phylicifolia and others), the 
Greenland Sandwort (Arenaria groenlandica), dwarf Birch, Dia- 
pensia lapponica, arctic lichens, and many other forms (about 55 
Qari 
in all), only found on some high mountains between Mount Wash- 
ington and labrador. 
Outside the tundra zone, that may have been rather narrow, 
there came sub-arctic forests with birch, alder, spruce and fir and 
associated flora and fauna. 
Deposits Formed by the Ice 
Ronkonkoma Moraine 
As mentioned above, when the edge of the last ice sheet had 
reached a line extending from Manhasset eastward to Montauk 
Point a rise of temperature set in. Wastage of ice now equalled 
supply from the north, and the ice border became stationary. 
Streams of melt-water furrowed the surface of the ice and issued 
rom beneath the ice. Boulders, cobbles, gravel, sand, silt, and 
clay that have been embedded in the ice melted out. The coarse 
material and part of the fine material was dumped on the spot. 
With material pushed together by slight movements of the ice 
edge it formed a more or less conspicuous irregular ridge consist- 
ing of small crests, cones, hummocks, and depressions. The ridge 
is from half a mile to about three miles wide and rises at many 
places 100 to 150 feet above the adjacent plain. This 1s the Ron- 
konkoma Moraine, so called for Lake Ronkonkoma in the central 
part of the island (Tig. 14). 
The bulk of the sand and part of the fine gravel were deposited 
outside the moraine. Soaked with melt-water the sand flowed out, 
aod 
eradually building up (during deposition) and reworking the 
rontal aprons that extend all 
=, 
gently sloping outwash plains or 
the way to the southern shore of the island. 
During movements of the ice sheet, blocks of ice were frequently 
dislodged from the solid ice mass to be buried beneath sand and 
gravel. Just as sawdust checks the melting of ice in a modern 
ice-house, so the sand could preserve the underlying ice blocks 
until the continuous ice edge had withdrawn from the vicinity. 
