12 
MUSEUM BULLETIN NO. 11. 
occur here in connexion with older granitoid and metamorphic 
rocks of different physical character. The topography of the 
lava areas differs in the abundance of cliffs, steep slopes, and 
flat tops, from the more gently rolling character of the areas 
underlain by the other rocks. In the Kamloops area north 
of Highland valley certain lavas of upper Miocene age lie upon 
granitic rocks. The contact between the two apparently 
follows the sides of the hills, and from an examination of the 
map one gains the impression that the lava acts as a hard cap 
which protects the lower rock from erosion. 
Evidences of disregard for the underlying structure are 
plentiful. Schists and granites lie side by side upon many of 
the rather flat topped hills in the Beaverdell area. In the 
Tulameen area the upland surface planes across a centroclinal 
basin of sandstones, conglomerates, and shales without apparent 
regard to the structure (Plate V and Figure 2, profile 6). In 
the Kamloops area nearly flat parts of the upland surface were 
seen to plane across lavas and agglomerates dipping up to 
angles of 25 degrees. 1 In all three areas the topography shows 
less of a relation to structure than a disregard for it, but a partial 
relation evidently does exist. 
To sum up: the character of the upland is very similar 
in the areas studied. It contains average regional slopes 
which vary from 3 to 6 per cent, with differences of eleva- 
tion upon it of from 1,500 to 2,000 feet within 10 miles. It 
seems to grow slightly flatter toward the north. The regional 
slopes are generally related to present drainage lines, although 
such drainage lines may be occupied by valleys lying far below 
the upland surface. This is not always true in the case of areas 
upon the border of the Plateaus, for here the surface is sometimes 
tilted away from the surrounding mountains. Cliffs, steep hill- 
sides, and flat tops occur in many places as local variations from 
the regional slope. The soil covering upon the upland is variable 
in thickness, and generally of glacial origin. The drainage is by 
wide valleys, and lakes and swamps are not uncommon. Fin- 
1 Oral communication from Mr. Bruce Rose of the Geological Survey of 
Canada. 
