Halation of the old and new Forest Trees. 



95 



not grown on the top of the layer of volcanic sand like the 

 living trees, but that they extended down through this layer to 

 the original soil beneath. The relation of the old and new forest 

 trees, as well as that of the stumps of the older forest, is shown 

 in the accompanying sketch (figure 3).* 



It is evident that the tree from the original soil beneath is 

 older than the eruption, and that since the tree was either dead 



1 Volcanic Ashes Lapilli Lc 



2 Original soil. 



3 Present forest tree 



4Tree of former forest killed by shower of Volcanic Ashes Sand ic- 

 5 Pit formed by the decay of old forest tree.^,. 



Figure 3. — Ixeladons of older and youiKjiT Forests to volcanic Sand. 



or killed at that time and has not comj^letely decayed, that the 

 eruption cannot have occurred many centuries ago. Of the time 

 that has since elapsed we have some measure in the age of the 

 living trees. In the same region the timber is cut for lumber, and 

 by counting the number of rings of growth it was found that the 



■ Reproduced from Bulletin 79, U. S. Geol. Survey, 1891, p. 20. 



