He pushed harder yet, and his left hand slid up over the back of his right.
“That’s what happened here. One edge of the earth crust, thousands of feet thick, rose right up and slid east a dozen miles or more, and then stopped. I believe the scientific fellers call that a fault. They call the eastern edge of this range the Lewis overthrust, because that’s where the overlapping stopped. Look—you can see all along here the precipices where the crust stuck out over the prairie, and all those parallel lines of different colored rocks are the different layers in the old crust. They find the skeletons and fossils exposed in ’em, which would be buried two or three thousand feet if you had to dig down.”
“But what I don’t see,” Joe said, “is why the top isn’t just level? Why are there any peaks and valleys?”
“It happened a few million years ago, son,” the man laughed. “I suppose things were some broken up at the first crack, and since then glaciers have come grinding down, and rains have fallen, and snows melted, and frosts cracked, and the ice and water have washed out cañons and carved the peaks. The high point was right where the undercrust stopped, back a dozen miles or more from the edge of the overthrust, so that became the Divide. That’s pretty near level in places even to-day. But east and west the running water has carved out long valleys and left harder rock sticking up as peaks. Up farther north old Chief Mountain sticks right out into the prairie, a tower of limestone, with everything else around it carved right away.”
“I get you,” said Joe. “I bet I’d have studied geography harder if I’d had these mountains to look at while I was doing it!”
The man in the seat behind laughed. “There must have been some shake up when the crack formed, and these six thousand feet of crust came up over.”
“I’d rather been some place else than standin’ right on ’em,” said the man in front.
The motor presently rolled through rather thick pine timber, up over a high ridge, and down into a valley.
“That’s Divide Mountain to the left,” said their guide. “Behind it is Triple Divide Peak. From the peak, the water flows to three oceans—west to the Pacific, east to the Missouri River, the Mississippi and the Gulf of Mexico, northeast to Canada and Hudson Bay. From here on all the brooks we cross are bound for Hudson Bay and the Arctic Ocean.”
In a short time they came to the foot of a lovely lake, and stopped at a group of buildings, built like Swiss chalets, on the shore.