Some scientists say hat the melt off of large glaciers and areas in the northern regions, cause extra weight and pressure upon the floor of the oceans. They attribute some of the increase in earthquakes and being more extreme in nature. Shifts in the floor can cause pressures that lead to volcanic activity. The biggest concern that we have now is the huge volcano beneath the ground of Yellowstone National Park in the U.S. If this over due eruption occurs, it will change all life in the Northern continent and around the globe, due to ash and influence upon needed sunlight to promote plant growth. Hopefully this may occur in thousands of years into the future, and we will have learned to deal with such problems before they occur.