
~ 

Parr. Srcr. iii] . SUBMERGED FORESTS 981 
observed in 1760 by Chalaourof to the east of Cape Sviatoj, was found 
by Wrangel sixty years afterwards to have been united to the 
mainland.’ 
§ 2. Subsidence. Itis more difficult to trace a downward move- 
ment of land, for the evidence of each successive sea-margin is carried 
down and washed away or covered up. ‘The student will take care 
to guard himself against being misled by mere proofs of the 
advance of the sea on the land. In the great majority of cases where 
such an advance is taking place, it is due not to subsidence of the 
land, but to erosion of the shores. It is indeed the converse of the 
deposition above mentioned (p. 276) as liable to be mistaken for 
proof of upheaval. ‘The results of mere erosion by the sea, how- 
ever, and those of actual depression of the level of the land, cannot 
always be distinguished without some care. The encroachment of 
the sea upon the land may involve the disappearance of successive 
fields, roads, houses, villages, and even whole parishes, without any 
actual change of level of the land. ‘The following kinds of evidence 
may be held to prove the fact of subsidence. 
Submerged Forests.—As the land is brought down within 
reach of the waves, and its characteristic surface-features are effaced, 
ay \ ‘ 
1 
A 1? 5 , » oat R 
Ag WW hl by. Sl =e tN Lona SSL 
Oe eee Oe oe te NG Seas Sal fe eee 

oa 




Fie. 71.—Sxcrion or SuBMERGED Forest (B). 
_ A platform of older rocks (e e) has been covered with soil (d d) on which trees (a a a) 
have established themselves. In course of time, after some of the trees had fallen (6), 
and a quantity of vegetable soil had accumulated, enclosing here and there the 
bones of deer and oxen (c ¢), the area sank, and the sea overflowing it threw down 
upon its surface sandy or muddy deposits (f /). 
the submerged area may retain little or no evidence of its having 
been a land-surface: It will be covered, as a rule, with sea-worn sand 
or silt. Hence, no doubt, the reason why, among the marine strata 
which form so much of the stratified portion of the earth’s crust, and 
contain so many proofs of depression, actual traces of land-surfaces 
are comparatively rare. It is only under very favourable circum- 
stances, as, for instance, where the area is sheltered from prevalent 
winds and waves, and where, therefore, the surface of the land can 
1 Grad. Bull. Soc. Géol. France, 3rd ser. ii. p. 348. Traces of oscillations of level 
- within historic times have been observed in the Netherlands and Upper Italy. Bull. 
Soc. Gécl. France, 2nd ser. xix. p. 556; 3rd ser, ii. pp. 46, 222. 
