Flight Training - July 2012 - 30

A 3-D RENDERING of Coteau des Prairies. Lewis and Clark dubbed the plateau "Mountain of the Prairie," but French explorers named it Coteau, or slope. It stretches 200 miles in length and is 100 miles wide.

I’ve seen those hills a thousand times from the ground. Driving on Interstate 29, I’ve seen those hills rise on the western horizon, a pretty break on the flatland prairie, and I know just enough about geology to have wondered—why are those hills there? Today I have a partial answer, and I want to see them from the air. While surfing the Internet one night, a picture showed up on the edge of my computer screen. It was a picture of my home, and it implied a story, so I spent some time reading. The Coteau des Prairies is just a pile of dirt pushed up into a moraine by a prehistoric ice sheet. That ice receded. When the next ice came—the famous Laurentide ice sheet—the Coteau des Prairies refused to move. It split the glacier and caused a deeper gouging of the land on each side. The hills are nothing spectacular, remarkable only because they are completely out of place, yet they even show up on the maps of Lewis and Clark as the Mountain on the Prairie. What I really want to see today is invisible. From the left seat of a rented Cessna 172, heading south toward those rising hills, I want to see history. I want to see the force of the Laurentide ice sheet moving down the continent, and I want to see the hills split the ice. Imagine the slip of paper in a theatre program, “Tonight the part of the very large glacier will be played by a very small airplane.” You could call it a type of situational awareness.

There is a wonderful quote by writer Reg Saner. “Destination,” he says, “is mere pretext for the real business of going to meet it.” The reason we practice and refine the grace of our landings, the reason we calculate wind-correction angles and time between waypoints, is because the joy of holding a machine in the sky is profound. The more we know about the land we’re crossing, the deeper that joy becomes. Examples abound. In summer, the approach to the International Peace Garden airport (S28) is calendar-art beautiful. Prairie farmland gives way to deep green forest near the Canadian border. Round hay bales and ponds dot the fields heading into Runway 28. It’s an easy landing, and the gardens are worth the trip. There is a famous glitch in Microsoft Flight Simulator here. For whatever reason, in the computer world a giant chasm opens on the far end of the runway and you can fly nearly 30,000 feet down toward the center of the Earth. There is no such hole in real life, but there is something underground. You cannot see it from the air and you cannot see it on the ground, even if you’re looking for it hard. But one look at a gravity map shows this part of the state has some of the densest rock possible. Landing at the Peace Garden, it seems, is landing on the summit of an underground mountain.

It makes a difference in the way you understand where you are. The North Dakota Isostatic Gravity Anomaly Map isn’t hard to find. Just Google “North Dakota Gravity Map.” Better yet, Google whatever state you live in. Along the same lines, ever wonder why sectionals sometimes warn about extreme magnetic variations? There is something called an aeromagnetic anomaly map. It all makes a difference. Long Island is a different place if you know the whole thing is a moraine pushed up by a glacier. The Grand Canyon is a different place if you know the Colorado River isn’t cutting down as much as the land is rising up, and the sight out your side of the airplane is

SHADED RELIEF of the Isostatic Gravity Anomaly illuminated from the northeast Grand Canyon.

TOP: MARTIN D. ADAMIKER TOP: MARTIN D. ADAMIKER TOP: MARTIN D. ADAMIKER TOP: MARTIN D. ADAMIKER

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Flight Training - July 2012

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