BIOGRAPHY OF A RIVER

B. Present terms and define.PROCEDUREI. Setting the stageA. Ask students to imagine that they are walking a trail in a wilderness area. Thewilderness area is bordered, over the hill from the river, by many acres wheremining was done 10 years ago. Grass and trees now cover that land. They havetaken a trail that leads up a ravine where a stream is running down toward theriver below. An old growth forest with very large trees borders the stream; it is shadedand cool in the ravine. As they walk upstream, they begin to notice a change in thecolor of the stream water. At first it is barely noticeable but gets progressivelymore intense. There is a definite red-orange color in the water. The farther theygo upstream, the more intense the color becomes; and they begin to notice redorangeparticles that have been deposited on the stream bottom where the wateris slower. Finally they reach the source of the stream, which is a spring coming outof a hillside. The red-orange color is very bright here, and red-orange particlesand deposits can be clearly seen where water is slowly seeping and bubbling out.B. Ask students to suggest possible causes for the red-orange color. Remind them ofthe mining activity and try to picture the topography of the land with the oldmines on the surface at the top of the hill from this ravine. Lead their thoughts inthe direction of possible minerals that might cause that color. Show the iron oresample and ask how iron might be dissolved.II.ActivityA. Put the iron ore sample into the weak acid. Agitate to increase dissolution.A crushed sample with more surface area will work best. If only a single chunk isavailable, you might put that in the acid a week ahead of this presentation. A brightred-orange color should appear on the rock surface where oxidation occurs, andsome should dissolve in the acid solution.B. To demonstrate earth disturbance from mining, give teams of two students a cookieand a toothpick on a sheet of newspaper. Tell each team that one person is to "mine"the chocolate chips or raisins out of the cookie using only the toothpick as a miningtool. The student must mine the cookie with as little disturbance as possible but3-85