IGNEOUS INTRUSIONS IN THE BLACK HILLS 35 
encroaching upon its base, while the plugs forming the Little 
Missouri buttes will become more and more prominent as the 
stratified rocks are removed from about them, and when the 
valley of the Belle Fourche shall have been broadened so that 
the waters of the river wash their bases, will form towers of the 
Mato Teepee type. 
The total amount of erosion that has taken place in the 
region about Mato Teepee cannot be accurately determined from 
the study of the local topography, but is certainly greater than 
the vertical distance from the bottom of the valley to the top- 
most crag of the Little Missouri buttes, that is, over 1500 feet. 
As shown by Newton, more than 4000 feet of Cretaceous and 
Tertiary strata have been removed from the Black Hills region. 
The Little Missouri Buttes—These buttes, as already stated, 
are formed of igneous rocks of the same character as those com- 
posing the Sun Dance hills and Mato Teepee. They are three 
in number and occupy the angles of a triangle, the distance 
between them being about three-fourths of a mile. Among the 
Indians they are said to be designated by a term which means 
“the buttes that look at each other.”’ 
The summits of the Little Missouri buttes are of bare rock, 
sometimes showing a columnar structure, and resemble the 
summit of Mato Teepee, except that they are less flat. The 
junction of the igneous rock with the surrounding Cretaceous 
sandstone is obscure, but the stratified rocks are well exposed 
near at hand and gives no indication of having been disturbed 
in bedding or altered in texture. Newton’ reports that in one 
or two localities near the base of the buttes a tuff-like rhyolitic 
breccia was found in which were imbedded fragments of both 
sandstone and rhyolite. ; 
The view of the buttes here presented, Plate II. (in which 
only two of them are seen, the third being to the left and beyond 
the field of view) is from a photograph taken at a locality on the 
Cretaceous plateau about a mile distant from the nearest hill in 
the direction of Mato Teepee. 
* Geology of the Black Hills, p. 203.: 
