300 ELEMENTARY GEOLOGY 
of depression the beaches mentioned above were built. 
The land then rose to a height slightly greater than 
the present. At that time trees grew in places that 
have since been submerged (Fig. 176), while the sea- 
level was assuming its present position. 
What changes occurred before this, cannot be so dis-. 
tinctly stated, for the further back we go in time, the 
less definite is the evidence. Nor can we tell satis- 
factorily the exact amount of the changes. Elevation 
brings beaches and other shore features above the water 
surface where they may be seen; but depression lowers 
them and hides some of the evidence from view. 
In these various changes, one striking feature is their 
difference, even in neighboring places. It is not a uni- 
form uplift or depression, but one somewhat irregular ; 
and the greatest recent changes have been in the north. 
In some places, as in the northern countries, the average 
recent change has been one of depression; hence the 
irregular coasts of northern lands; but im other places, 
as on the coasts of Chile and Peru, the average move- 
ment has been a rising, and therefore the coast line is 
very regular. 
The Changes a Result of Land Movement. — In the 
changes in level of the sea and land, it is often asked 
whether there has been an alteration in sea-level, or 
an actual movement of the land. In answering this 
question, we must first recognize the fact that there 
