I would like to quote from Physical Geology by Leet and Judson, one of my text books:
“The Rockies are Fold Mountains; fold mountains provide us with spectacular examples of deformed rocks. The numerous folds of anticlines and synclines have been sliced open to view by streams cutting into them as the land moved upward from forces causing a rise in elevation. The lands against which these rocks were pushing now stand as plateaus; broad, high-standing regions underlain by sedimentary rocks relatively little deformed” (Leet & Judson, 1965, p.264). Picture a horizontal zigzag like a piece of paper that is pleated on one half and flat on the other and then the whole thing is pushed together and bent upward – so that half is crumpled and half is relatively flat, but the whole thing is under elastic compression and bowed upward. Think of a box compactor full of rubber balls and floating on top is a piece of sheet rock precisely cut to completely cover the area from side to side and from end to end. Now have someone turn it on while you stand in the middle. Wait until the ends start to come together and the balls are compressed and the sheet rock starts to bend upward. This is a mental model of the conditions in central Montana about 50 million years ago. So now I would like to point out that the Bauman Impact Structure sits squarely on the border between the Rocky Mountain Chain and the Great Plains of North America. The hexagonal ring is right on the edge between the folded mountains to the west and the raised plateau to the east. The crust in this area of central Montana would have been relatively weak and probably pocketed with hot spots of magma, even though it was relatively little deformed at the time. Still, the rocks under it were under tremendous compression and starting to bow upward, however they had not reached their elastic limit yet. To the east was a relatively flat plateau that continued on for hundreds of miles. To the west was, and still are, the numerous folds of the Rocky Mountains that had developed into a series of basically parallel ridge lines that lie about 30 degrees from geographic north. My point is that the ridge line of the Snowy Mountains is about 80 degrees from geographic north, a huge departure from the general trend of the mountain ridges that begin less than 100 miles away. This departure from the general trend should be an indication that the forces that created the Snowy Mountains are separate from the forces that created the Rocky Mountains immediately to the west. Back to our mental picture of you standing in the middle of the compactor; now jump on the sheetrock. What do you think will happen? The surface will break into pieces and the whole mass will rebound and increase in elevation. I believe the shock wave from a large meteor impact triggered a combination of elastic, plastic and brittle deformation reactions. The crust of the earth was under stress from below and did not have the strength to withstand the strain of impact. Hence we have fractures, breaks, and uplifted plates. One of these plates, the Snowy Mountain plate, looks like an asymmetrical fold where the strata was pushed up and severely stretched on the steep side of the fold. The breaking point of the upper strata was exceeded and the upper layers of rock broke away, but the middle and lower strata were pliable enough to bend. They were bent up and bent over, forming the folded block we see today; comprising the south face (south limb), top ridge (east/west strike), and north slope (north limb) of the mountain block. It looks like the kind of fold that would be developed if you took your boot and kicked the surface of a rug in such a way that it created a single fold. Better yet, cover the rug with mud and let it dry a little bit for more realism. The upper crust would crack and fall away but the bottom layer would bend and remain part of the fold. According to current understanding; Fold Mountains created by compression always result in a series of parallel folds that form together, so that there is more than one ridge line, meaning more than one fold. The Snowy Mountains are a single fold that stands alone and is therefore out of the ordinary and probably not caused by common compressional forces. It looks like a gigantic scuff mark caused by something that ripped into, then dragged and deformed the outer skin to leave a giant scab on the surface of the plains. Consider the results of an extremely shallow angle of impact from an extremely large object.