The geographical poles -- the north and south tips of the axis that the Earth spins around -- wobble over time due to small variations in the sun's and moon's pulls, and potentially to motion in Earth's core and mantle. But changes on the planet's surface can alter the poles, too. They wobble with every season as the distribution of snow and rain change, and over long stretches as well. Roughly 10,000 years ago, for example, Earth woke up from a deep freeze and the massive ice sheets sitting atop what is now Canada melted. As ice mass fled, and the depressed crust rebounded, the distribution of the planet's mass changed and the north pole started to drift west. This pattern can be clearly seen in data from 1899 onward. But a recent zigzag in the north pole's path (and the opposite movement in the south pole) suggests a new change is afoot.
Oregon, California, the federal government and others have agreed to go forward with a plan to remove four hydroelectric dams in the Pacific Northwest without approval from a reluctant Congress, a spokesman for dam owner PacifiCorp said Monday. Tearing down the dams would be a major victory for tribes that have fought for years to restore the river for salmon they rely on for subsistence and ceremony. The move also could breathe new life into a struggling effort to allocate more water for farmers and ranchers in the drought-stricken Klamath basin. read more