PEBBLE -- From the air, the old caribou trails are still visible as tracks across the dry tundra, though the caribou are largely gone.

Once the Mulchatna herd swarmed the surrounding hills 200,000 strong, but it began a steady decline late in the 1990s. Now the herd is about a quarter of its peak size, and the bulk of the population has moved farther southwest along Iliamna Lake. No one knows why.

"Everything changes," says helicopter pilot Glenn Summa.

Ninety million years ago, dinosaurs roamed here, and beneath their feet the earth's volcanic core shot a stream of molten, copper-rich rock skyward. The dinosaurs didn't care. Neither did the mastodons or saber-toothed tigers or short-faced bears or any of the other animals that arrived later with the glaciers of the Ice Age only to follow the dinosaurs into extinction.

None of them knew what lurked beneath the ground. Nor did the miners who swept across the north in the 1800s, wandering constantly -- much like the caribou -- in search of mineral riches. They panned some gold out of the main creeks draining into salmon-rich Iliamna Lake, but there was never enough color to spark anyone's interest in large-scale mining. Cominco Alaska Exploration, a major mining company, did poke around in the area in 1986 and discover what was originally called the Pebble Beach copper prospect in an area that reminded geologist Phil St. George of the Pebble Beach Golf Course in California. But by 1992, Cominco had rejected any idea of development.

The estimated 3 million tons of copper were bound up in a billion tons of rock in a place far from nowhere. Development costs for roads, a port and a mill were staggering. Cominco walked away, and by 2005 an Alaska state study land review for the area concluded "the most significant mineral occurrence within (the surrounding country) is perhaps the Fog Lake (Fog Pond) gold prospect, considered to be a gold- and silver-bearing prospect with minor copper values."

Fog Lake today remains a potential mineral development lost in the fog like so many other mining dreams for Alaska. But about the time the state was noting the possible value of Fog Lake, the real value of something called the Pebble prospect began to explode onto the scene, 40 miles to the northwest on the opposite side of 77-mile-long, 22-mile-wide Iliamna Lake.

Further probing of Pebble by Northern Dynasty Minerals early in this decade revealed a concentration of copper beneath the old Pebble Beach, even more gold, and a lot of valuable molybdenum. At the same time, worldwide demand for copper was growing, shifting the economics of development. Development costs that had been too high for Cominco to even contemplate were starting to look like they might at least be worth investigating, along with the size of that copper deposit.

All of which sparked a political explosion in what would come to be called "the headwaters of Bristol Bay."

A simple issue

If you are a tried and true environmentalist, any question about developing the Pebble mineral deposit has a simple answer: The risk isn't worth it. There could be an accident. Mine waste could leak into surrounding waters. Some salmon -- some portion of the 30 to 40 million that return to Bristol Bay ever year -- could be threatened. Serious environmental damage could take place. Yes, the mine would create some jobs, but they would be temporary. And, as is usually the case in the business world, most of the profit from the mine would go to the mining companies and their shareholders. As the television advertisement says, "they get the gold, Alaskans get the toxic waste."

No such concerns were raised the last time Alaska saw the development of a major copper mine at the start of the 20th century. Between 1911 and 1938, the Kennecott Mine ripped $200 million worth of copper out of the Wrangell Mountains near McCarthy, concentrated it in a most environmentally unfriendly way, dumped its waste into the headwaters of the Copper River, and shipped the ore Outside.