Greenhouse and Icehouse Earth - Causes of Icehouse Earth

Causes of Icehouse Earth

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 CO₂ 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 seem to play a crucial part in Icehouse Earths because they can bring forth cool waters from very deep water circulations that could assist in creating ice sheets or thermal isolation of areas. An examples of this occurring are the opening of the Tasmanian gateway, 36.5 million years ago that separated Australia and Antarctica and which is believed to have set off the Cenozoic icehouse (Exon, Kennet and Malone), and the creation of the Drake Passage 32.8 million years ago by the separation of South America and Antarctica, though it was believed by other scientists that this did not come into effect until around 23 million years ago. The closing of the Isthmus of Panama and the Indonesian seaway approximately 3 or 4 million years ago may have been a major cause for our current Icehouse state. For the icehouse climate, tectonic activity also creates mountains, which are produced by one continental plate colliding with another one and continuing forward. The revealed fresh soils act as scrubbers of carbon dioxide, which can significantly affect the amount of this greenhouse gas in the atmosphere. An example of this being the collision between the Indian subcontinent and the Asian continent, which created the Himalayan Mountains about 50 million years ago.