MINNESOTA KIVER VALLEY 239 



its earlier one. Nothing appears, therefore, in erosion of the hill to pro- 

 duce terraces in the valley, and nothing also in the form of the hill to 

 produce any other marked result than the swerving of the river "Warren 

 gradually to the right of it. 



The making of the terraces may, however, be attributed to the third 

 factor, namel}^, to that of unequally resistant geologic formations, which 

 were cut into as the river evaded the Bedstone quartzite. These evidently 

 were the intact Cretaceous and Glacial deposits. Since the pre-Glacial 

 drainage here ran, as before stated, north of the Courtland quartzite area 

 and the inter-Glacial valley was on the east side of it, the post-Glacial val- 

 ley which runs on the west side is therefore a new course, from New Ulm 

 passing Bedstone, and accordingly the geologic formations may be sup- 

 posed to have been intact there when river Warren began its valley. Some 

 portions of these formations are still found between Bedstone hill and the 

 river. 



The formations which were eroded here by the river are the Young 

 drift, the Old drift, and the Big Cottonwood formation, and each of these 

 comprises hard and soft parts, such as to cause the erosion of a stream 

 through them to progress by stages. The more resistant parts are (1) 

 the boulder-clay of the Young drift, (2) that of the Old drift, (3) the 

 tough clay beds at the top of the Big Cottonwood formation, and (4) the 

 red shales at a lower horizon in the same. The river terraces correspond 

 to the tops of these resistant parts, having formed by the erosion of the 

 softer parts, namely, a loose gravel bed at the base of the Young drift, 

 another at the base of the Old drift, and the thick beds of loose coarse 

 sand below the top of the Big Cottonwood formation. Whenever the 

 river cut down to one of these at one point before others, the deepened 

 channel could be readily widened by lateral erosion of the softer bed and 

 undermining of the harder ones, from which presumably resulted terraces 

 bounded by steep scarps, such as are now seen. 



The si^rface of the terraces show generally a gradient greater than that 

 of the present river, and they are covered with coarse gravel, and they 

 appear to be remnants of rapids and rapidly sloping channels passing Bed- 

 stone. Yet the terraces, although largely detached or interrupted, show 

 generally a correspondence one to the other much as terraces of sub- 

 sidence do. Their correspondence may be due rather to the control of 

 the eroded geologic formations than to gradient of the river. 



On the right side of the valley the highest, or 940-foot, terrace, resting 

 on Young drift, forms the site where the cemeteries are located, on the 

 west of New Ulm. The 910-foot terrace, resting on Old drift, forms the 

 high central part of New TJlm city. The 870-foot terrace is represented 

 on the one side of the last by the abandoned channel back of the city 



