Vol. 6, 1920 
GEOLOGY: R. A. DALY 
247 
beaches of Labrador was impossible, and with the data in hand serious 
belief in the hypothesis of a eustatic change was withheld. 
However, that explanation was recallei by the discovery of new facts 
during recent field studies on the shores of New England, Florida, and the 
Samoan Islands. Meantime Goldthwait had made a careful study of the 
St. Lawrence strand, to which he gave the name "Micmac terrace;" the 
results of his leveling agree so well with those made in the other regions 
mentioned that the suspicion of past years became a hypothesis deserving 
more attentive consideration. 
For the opportunity to collect data from the two tropical regions the 
writer is indebted to Dr. A. G. Mayor, Director of the Marine Laboratory 
of the Carnegie Institution of Washington. 
In his excellent account of the Micmac terrace, Goldthwait noted the 
nearly uniform level of its inner edge at about 20 feet above high tide, as 
well as its relatively great strength and continuity, with width varying 
from a few feet to 1.5 miles or more. Though only a part of its width is 
due to wave-cutting and though the formations affected are weak, the 
higher level of the sea must have been steadily kept for a large fraction of 
post-Glacial time.^ Farther east in the Gulf of St. Lawrence, on Anticosti, 
and again in Nova Scotia, Twenhofel has found wide terraces at about the 
same level. ^ 
A similar feature characterizes the coast of Maine, as emphasized 
in the folios and monographs of the United States Geological Survey and 
as confirmed by the present writer. 
Mayor had already found wave-cut rock benches, about 8 feet above 
high tide on all sides of Tutuila, the largest island of American Samoa. ^ 
The island is 16 miles long. At its eastern end is Aunuu island, and about 
60 miles farther east is Tau island of the Manua group. The writer found 
very fine wave-cut benches at 8 to 10 feet above high tide on Aunuu and 
Tau, and others at the same general elevation on Olosega island, 7 miles 
west of Tau. The distance between the most widely separated benches 
is 75 miles; nowhere in that long stretch did the bench crests depart es- 
sentially from a constant level. Explanation by local uplift was at once 
seen to be highly improbable, for crustal uplift of such uniformity is un- 
known to geology. 
Eight or ten feet of bench elevation does not, however, measure the total 
of recent emergence in Samoa. At several points in Tutuila large sea- 
caves were found. Their floors varied in height, from 14 or 15 feet at 
their mouths to 25 feet at the back walls of the caves. Many caves of 
similar forms and cut in similar rocks are being made by the surf of the 
present day. The lower lips of these newer caves are characteristically 
4 to 6 or more feet below high-tide level and the floors rise inwards to 
heights of a few feet above high tide. Hence, the emerged caves were 
cut when the sea-level was nearly 20 feet higher than now. That assump- 
