Australian geologists have solved the mystery of what triggered and sustained an extreme ice age that gripped the Earth more than 700 million years ago. The study, published in the journal Geology, reveals how the Earth's thermostat works and how sensitive the climate is to changes in atmospheric carbon dioxide. Low volcanic activity and rock weathering The researchers used plate tectonic models to simulate the evolution of the Earth's surface and carbon dioxide emission from underwater volcanoes. They found that the onset of the ice age coincided with a period of very low volcanic activity, which reduced the amount of...