The second most common question students ask in science classes is “How do we know that?” Good question, tough answer. Good because “how” is what science education is-or should be-all about. Tough because the answer to the question often involves exactly the science and mathematics the student has yet to learn.
Constructivist and inquiry based learning were designed to address this dilemma. Constructivism is the (excellent) technique of learning by constructing new understanding upon established knowledge. Inquiry is the process of discovering information through guided discovery. They are complimentary approaches, and emphasize understanding of science as a unique and valuable way of understanding the universe, as opposed to a list of facts easily recited, and forgotten, on a multiple choice exam. Ironically, the best aspects of learning science exactly reflect the best parts of doing science-it’s a constructivist process. The project I’m working on this week is the result of literally 50 years of people learning something new by asking “why does that happen?”
Over the next week I’ll be answering the “how do we know that” question first hand. I’m off to the Pacific Northwest to help out a friend “service” a deployment of 60 seismometers spread from Copalis Beach to Enumclaw, Washington. As we’ll find out, this kind of work isn’t obviously sexy, but it sure is fun. And illustrative, both of how hard it is to do science right, and how hard it is to teach science right. First, though, we have to get from Kansas City out to Shelton, Washington.
“That”-what we know-is the structure of the earth from the surface down to about 60 mile depth. Driving 60 miles across the earth takes an hour, but getting 60 miles deep is impossible. It’s important to remember that we have no first hand experience with the structure of the earth below about 3 miles down. The deepest mine on earth is only 2 miles deep, and the deepest hole ever drilled is a mere 9 miles deep! So all our knowledge of earth’s structure comes from remote sensing, largely from the study of the waves released by earthquakes and subsequently reflected, refracted and twisted as they travel thorough the earth. The quick answer to the question of how we know earth’s interior structure is simple: careful interpretation of subtle differences in the way earth transmits the sound waves generated by earthquakes. Of course, that kind of answer is the same thing as saying babies come from the hospital.
The details of all this are where the fun is, and this week is all about sharing the fun with you. Even the flight is worth sharing. Heading west northwest from Kansas City toward Seattle provides the greatest geological cross section of the continent one could hope for. Kansas may well be flatter than a pancake, but a slight dusting of snow brought out the boundaries between the wheat fields, divided by the USPLSS into quarter-mile packets set between orthogonal range roads. (The USPLSS is a wonderful testimony to rationalism, Jefferson, and hubris. I love everything about it. Read all about it.) By the time we got to western Nebraska, the snow had begun to bury those same range roads, and the fields had grown to a mile across. (Fewer people, larger farms.) We left the plains behind at the Wyoming border, and anyone can tell that the world has changed. The checkerboard fields had disappeared , replaced by the hogbacks, flatirons and hanging valleys of the Grand Tetons. The Midwest, geologically quiet for 250 million years, was gone, replaced by an active noisy continental margin.
Just over three hours north west of Kansas City, I looked back towards home and saw that all the gullies, streams and rivers were heading back the way I came. Ahead, all the water pours westward-the continental divide. We all know water flows down hill, but the hills here point in different directions, due in part to the complicated mixture of forces acting on the western edge of the continent. Then the checkerboards reappear, stuck in long, flat valleys of sand crammed between mountain ranges, a sure sign that we have left the Rockies for the Basin and Range province. Then the first volcanoes show up, a sure sign that we are in a new world yet again. These first cones are stubby and squat, barely rising about the low ground fog forming in the late afternoon sunlight. The view is oddly martian-the stationary clouds hover at the edges of the mountains like a Harryhausen special effect-cool, but not quite real. Think about it-just a few hours from Kansas City and I’m flying over earth so hot that molten rock made it to the surface. Why there and not KC? Why when we reach the Cascades is there a line of volcanoes-no longer stubby and squat-stretching south toward California?
This last question-why are the Cascades where they are, how does the earth melt to form these things and how do we know it are for tomorrow.
Tags: Geology, Teaching Science
