The volcanic processes will intensify, obviously some volcanoes will erupt producing more CO2 and sulfur, polluting the land and water. The temperature of gazes in atmosphere will increase causing the glaciers to melt, increasing the sea level. That would cause flood and even tsunami (volcanoes aren't only above the ground level, they are under water too). Billions of life forms in the oceans will die i effect of pollutants, shift of temperature (again volcanoes), what would lead to extinction of many species feeding on them, both water and land animal. Imagine the rest for yourself.