Earth ozone layer due to the subsequent conversion of atmospheric into. The ozone layer blocks ultraviolet solar radiation, permitting life on land. Other atmospheric functions important to life include transporting water vapor, providing useful gases, causing small meteors to burn up before they strike the surface, and moderating temperature. This last phenomenon is known as the greenhouse effect: trace molecules within the atmosphere serve to capture thermal energy emitted from the ground, thereby raising the average temperature. Water vapor, carbon dioxide, methane, nitrous oxide, and ozone are the primary greenhouse gases in the atmosphere. Without this heat-retention effect, the average surface
Greenhouse and icehouse Earth cooler globally. The Earth is currently in an icehouse stage, as ice sheets are present on both poles and glacial periods have occurred at regular intervals over the past million years. The causes of an icehouse state are much debated, because not much is really known about the transition periods between greenhouse to icehouse climates and what could make the climate so different. One important aspect is clearly the decline of CO in the atmosphere, possibly due to low volcanic activity. Other important issues are the movement of the tectonic plates and the opening and closing of oceanic gateways. These