Field Trips

Sudbury Structure Field Trip
Prepared by Carol Christopher, Editor, AAPG Bulletin

The Sudbury Structure bus tour had plenty to offer: unusual rocks, flora and fauna, scenic views of waterfalls and fall foliage, and an abundance of fresh air and exercise.

We walked the railroad tracks at the discovery site, clambered over outcrops as we viewed ore-rich rocks, and trailed down busy highways as we strained to hear the guides above the roar of the ore trucks.

The trip included food for the body and food for thought. Was this large peanut-shaped structure with rich ore deposits in the outer rings and volcanic rock to the south created by meteorite impact or a violent volcanic eruption? The Onaping Formation, the most controversial part of Sudbury geology, is called a fall-back breccia by those who favor a meteorite impact, and an ash-flow tuff and lavas by the supporters of a volcanic origin.

The Sudbury ore was exposed during construction of the Canadian Pacific Railway in the late 1800s. The mines are best known for copper and nickel, but the ore also includes cobalt, platinum, gold, silver, selenium, and tellurium.

We gazed at gossan deposits and melt bodies along road cuts, viewed changes in composition to the granophyre, and visited the Copper Cliff Mine (first producer of Sudbury ore) area. We were treated to a late-afternoon view of shatter cones, formed by passage of shock waves through rocks, before returning to Sudbury, content with our collections of rocks, leaves, and fond memories.

Big Nickel/Science North Field Trip
Prepared by Winfield Swanson, Editorial Services in the Sciences

What's out: 8-ft-wide tracked drifts; rail cars; dynamite; timber to supports; mining accidents; barren landscapes.

What's in: 15- to 18-ft-wide trackless drifts; trucks and other wheeled vehicles; B-line, nonelectric blasting caps; rock-bolts and screen; bigger and fewer holes; regulations, second exits, and emergency rescue teams, plans, and refuge rooms; regreening efforts.

So says Elgin, who began working underground in 1960, and now introduces groups such as ours to the Big Nickel Mine in Sudbury. He took a group of 20 AESE members through the demonstration mine, dug solely to teach techniques to aspiring miners and to show visitors what's going on underground.

We took the cage [elevator] down to the drift [tunnel]. About 9 ft wide and 9 ft high with a pair of tracks running down the middle, the drift is typical of a 1960s mine. Today drifts are large enough to accommodate wheeled vehicles (with diesel fumes--larger space allows more air). The 4-in pipes about two thirds of the way up the wall contain compressed air to run the drills (120 lb/in2); the 2-in pipes are for water.

Surveyors tell miners where they want to go and how to get there. One of their tools is a diamond drill, that is, a drill with a diamond bit that's hollow in the center so cylinders of rock samples can be extracted from as deep as 600 ft. When the cylinders are analyzed for ore, the surveyors can map its location. Of all the rock taken out of a mine, 97% is waste. At Sudbury, ore averages 4% combined copper and nickel. (The rock is "ore" if it can be sold for a profit; otherwise it's mineralized ground.)

In mining, you cut to get the ore out and fill to prevent cave-ins. First drill three or four holes into the stope [the wall where the ore is]. Fill the holes with explosive (ANFO--Ammonium Nitrate Fuel Oil--nowadays) and ignite the caps attached to B-line. Then push the fallen rock down the 200-ft-diameter hole made previously in the floor so that trucks waiting on the next level down can scoop the ore up. Finally, fill in the blasted area with tailings mixed with cement.

Even though drifts are now held up by rock-bolts instead of timbers, fire is still the major risk in mining, but by the time Elgin finished describing all the safety features of the contemporary mine, mines seemed safe as houses. In fact, nowadays more accidents occur in construction than in mining. Then Elgin showed us the refuge, a pressurized room equipped with fresh drinking water, where in emergencies miners enter and bolt and seal the door with clay. The miners are alerted to the emergency by the odor of ethyl mercaptan--stench gas--in the air line. Only the rescue team can open the door. (Lest the mind stray to "Aida," Elgin did say he'd only ever been sealed into the refuge room during a drill.)

The Big Nickel Mine uses some of its underground rooms (24C year-round) to germinate the millions of tree seedlings (white pine, red pine, and jack pine) needed for Sudbury's regreening program. The program, begun about 20 years ago, is one in which Big Nickel can be justly proud, as its museum's before and after photos illustrate.

In the "good old days," miners cut trees to make roasting beds. On a layer of logs they put a layer of ore and then burned it so the rock would release the minerals. The process also released so much sulfur that it blackened the surrounding rocks and killed all the plants. Now a layer of lime must be put down to neutralize the acid in the soil before seedlings can be planted.

Science North, the science museum, is composed of two buildings joined underground. Exhibits occupy a hexagonal structure built into solid rock next to Ramsay Lake. A smaller building houses non-exhibit activities (admission, IMAX tickets, orientation, shop, restaurant, offices, etc.). Appealing as the design is now, 40 years ago when Science North was begun, it must have engendered considerable comment. (It might be instructive to learn how the architect got the design approved.)

The visitor leaves the admission area and follows the underground tunnel past a sheet of falling water and past water running along the rocks into which the exhibit hexagon is built. The large, ancient fault is made even more impressive by the suspended skeleton of a whale whose carcass was washed ashore and was rescued by museum staff members.

The remainder of the hexagon is filled with interactive displays (panning for gold, computers, sound and music, seashells, the human body and its parts, etc.), all thought-provoking and mind-expanding for children of all ages. But my vote goes to Ralph the porcupine, with the friendly beaver as runner-up. Ralph has lived at Science North for several years, long enough so that his body has adjusted to his environment: in summer Ralph grows his winter coat (long fur over quills) when the air conditioning is on; in winter he assumes his summer coat (quills without fur) when the heat is on. In addition to the porcupine and the beaver (which is sometimes allowed to go for a walk), the museum houses various fish and a rough-legged hawk whose wing had been shot.

Outside, the complex has been finished off with a few plants that can be induced to grow between the rocks and a boardwalk along the lake.