How are some isotopes considered radioactive

Some isotopes are stable, but others are radioactive. An isotope will be radioactive if its nuclei are unstable. Large atomic nuclei, with more than 93 protons and their associated complement of neutrons, are inherently unstable. Uranium and plutonium are examples of such elements.

glacial erosion, the picking up and movement of earth beneath a glacier, is also referred to as plucking. erosion and transportation of individual pieces of bedrock, especially large "joint block occur as a result of this glacial erosion. plucking is type of erosion in which rocks become frozen into the bottom and sides of the glacier.as the glacier moves downhill it 'plucks' the rocks frozen into the glacier from the ground.