It wasn’t uniform, though. The quake caused tilting, which showed up in the way the north side of Hebgen Lake had sunk eight feet, while the south side of the lake, docks, boats, etc., were sticking eight feet out of the water. The quake also caused many sink, or more properly, blow holes. These phenomena are also known as sandspouts. Water, compressed and forced up and out by quake action washes out layers of sand sub strata. The overhead surface areas naturally drop into the hole, leaving a puzzling hunk of slumped ground—separate from the normal scarps—as big as 15 × 50 ft. in area. The Montana-Yellowstone quake sent seismographs jiggling as far away as New Zealand. It caused fluctuation of water level in wells as much as ten feet in nearby Idaho, a tenth of a foot in Hawaii, 3,200 miles away, and .01 ft. in Puerto Rico. The huge concrete Hungry Horse Dam, near Columbia Falls, Montana, 250 miles NW of the quake area, showed measurable displacement as a result of the quake. In remote Seattle, the diminished tremors were still strong enough to break loose the floating amphitheatre in Lake Washington. [Illustration: Rock Cr. Camp] [Illustration: Collapse of Dolomite Buttress] [Illustration: Camp as buried by landslide] But by far the most spectacular effect of Montana’s Earthquake was the huge landslide at the mouth of the Madison Canyon. At the site of the slide, a relatively strong and nearly vertical layer of dolomite rock supported a huge bank, or mountain, of comparatively unstable schist and kept it from sliding into the valley in the same way that a retaining wall keeps a hillside terrace from slipping downhill. The tremendous shock waves of the earthquake fractured this dolomite buttress, and some 43 million cubic yards, or 80 million tons of rock, timber, and other mountainside debris cascaded off the slope, hurtled into the canyon, and surged up the opposite side, carrying huge trees and house-sized boulders as if they were weightless, hollow toys. When this huge mass whomped down onto the river bed, it forced out the water and air trapped underneath at hurricane velocity. The huge slide spurted mud, air, and water with such force as to send two-ton cars sailing through the air, and to grind others to suitcase thickness against the rocks. All this happened in seconds. It would take eight seconds for the mass at the top of the mountain to fall to the valley floor 1,200 ft. below. At the time it reached this point, the mass would be travelling 174 miles per hour. The time it took to zoom half-a-mile across the valley, up the opposite canyon wall, then split and flow three-quarters-of-a-mile up and down the valley (the slide lies one-and-a-half-miles-long in the valley), was less than thirty seconds!