-GLACIATION IN THE TELLURIDE QUADRANGLE 719 
fessional Paper 67, Mr. Howe has considered their occurrence and 
causes at length, and has called attention to the fact? that under 
certain circumstances masses of material moved by landsliding and 
masses deposited as glacial moraines may resemble each other so 
closely as to give rise easily to errors in interpretation. As criteria 
in such cases Mr. Howe says that “‘recourse must be had to strictly 
geologic evidence—that is, the condition and character of the 
material and its relation to rock in place.” 
In a discussion of the same problem as presented in the Uinta 
Mountains, Mr. Wallace W. Atwood? lays especial emphasis on the 
value of topography and topographic relations in the determination 
of doubtful cases of this kind, saying that ‘‘the chief criteria used 
have been, first, the topography of the material; second, the topog- 
raphy of the basin or valley affected; and third, the topographic 
relations in the basin or valley.” 
It is of course necessary constantly to bear in mind the fact 
that, so far as the region under consideration is concerned, the 
question usually most difficult to decide is not whether a given mass 
of material has its present form and position as a result (1) of 
glacial action exclusively, or (2) of landsliding exclusively; but that 
it is as a rule a very different one, embracing two distinct phases, 
viz.: (a) to determine with some degree of accuracy what share 
each of the two classes of agencies referred to above may have had 
in determining a given arrangement and location of débris; and 
after this is done, (6) to decide how completely the work of each 
class of agencies is to be represented on a map showing the geology 
of the region. Or, stated briefly and in order, the points to be 
ascertained about such doubtful areas are: 
I. Agencies involved. 
1. Glacial action to the exclusion of landsliding. 
2. Landsliding to the exclusion of glacial action. 
3. Glacial action with later landsliding. 
4. Landsliding with later glacial action. 
5. Various successions and alternations of glacial action and 
landsliding. 
1 Op. cit., pp. 16 and 17. 
2 Professional Paper 61, U.S. Geological Survey, pp. 63-65. 
