40 THE FLOOR OF THE OCEAN 



present rates of uplifting of the same region as determined by 

 precise leveling. Here the figures mean the numbers of milli- 

 meters of rise during one year. We see that the one set of lines 

 roughly parallels the other. Moreover, in this region the rates 

 of tilting as determined by tide-gage and spirit-level are almost 

 identical with each other and also comparable with the rate of 

 tilting of a sea-beach that was built 7000 years ago. 



We wish to know the amount and distribution of the stress 

 — unbalanced, inward pressure — now felt by the subcrustal 

 material of the Fennoscandian region. Both desiderata are ob- 

 tained as soon as we learn the dimensions of the negative load 

 still remaining in the glaciated tract. The maximum stress 

 must be centered near the Gulf of Bothnia, the place of thickest 

 ice at maximum glaciation. To find that stress we need a good 

 estimate of the weight of rock matter that will be restored to 

 the central sector when, in the distant future, the upheaval 

 ceases and the earth's crust comes to equilibrium. Such an 

 estimate has been reached in two different ways. 



The first way was followed by Dr. E. Niskanen of Finland. 

 The rate of upheaval since the beginning of post-Glacial time, 

 nearly 9000 years ago, has been decreasing, and a reasonably 

 definite law of the decrease established. With the help of this 

 law Niskanen has been able to estimate the amount of uplift 

 still to come. He has also prepared the map of Figure 20, 

 showing the amounts of future uplift to be expected along the 

 radii of the glaciated tract, from the central area out to the 

 Russian territory on the southeast. The amounts of the uplift 

 during the millennia to come are indicated in meters. The 

 lines of equal displacement, needed to correct for the negative 

 load on the Finnish sector of the earth, are closely parallel to 

 those of equal displacement in the tide-gage map covering 

 Finland. See Figure 18. 



To effect the future uplift, subcrustal material must flow in 



