G105 Chapter 3
Popular in Earth: our habitable planet
Popular in Geology
This 2 page Study Guide was uploaded by Bruce Kwon on Monday March 28, 2016. The Study Guide belongs to GEOG-G105 at Indiana University taught by Bruce Douglas in Spring 2016. Since its upload, it has received 37 views. For similar materials see Earth: our habitable planet in Geology at Indiana University.
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Date Created: 03/28/16
1. Volcanoes are conduits linking deep mantle processes to atmospheric composition and hence climate; they exhale large amounts of water, CO2 and SO2. over geological timescales, volcanoes have an important role in the carbon cycle, but in the recent past their contribution to atmospheric CO2 has been overwhelmed by the anthropogenic flux 2. The radiative effects of major explosive eruptions can be large, reducing the amount of solar radiation reaching the earth' surface by more than 10%. The effects of most explosive eruptions, however, are short-lived (2-3 years), as aerosols fall out of the stratosphere. Due to the long response time of the earth's climate system as a whole, brief volcanic events do not have a significant effect on climate. 3. Eruptions of flood basalts such as those of the Columbia river province may involve effusion of more than 1000 km^3 of sulfur-rich basalt lava over periods of 10-100 years. As these eruptions are sustained over longer periods than great explosive events, their radiative and environmental effects may be more profound. The close coincidence in timing between great episodes of flood basalts in earth history with major mass extinctions, such as those ar the cretaceous-tertiary and palaeozoic- mesozoic boundaries, suggests that mass extinctions may be linked with the environmental and climatic effects of the flood basalts. 4. Climate models using highly simplified continental configurations suggest that a tropical ring world would be significantly warmer than a polar cap world. It is thought that the geography of the earth may have approximated to the former between 100 Ma and 600 Ma, and to the latter (with one polar ice cap) during the late Carboniferous. 5. It is thought that the changing distribution of continents in response to plate-tectonic processes affects global climate on a million-year timescale, through its effect on the radiation budget, and hence indirectly on the hydrological cycle and weathering (which affects the CO2 concentration of the atmosphere). 6. The break-up of Pangaea began at about 200Ma. The opening of a low latitude seaway may have contributed to global warming in the cretaceous, at about 100 Ma. Around this time, deep water masses were probably warm and very saline, having formed at low latitudes. It is thought that thermal isolation resulting from the initiation of the Antarctic circumpolar current at 25Ma accelerated cooling of Antarctica and the growth of the south polar ice cap 7. Relative sea-level change results from a combination of eustatic and isostatic sea-level change. Eustatic changes are global in extent, whereas isostatic changes result from local or regional uplift or subsidence of the lithosphere. Eustatic sea-level changes are due either to changes in the volume of ocean waters (resulting from the formation and melting of ice sheets), or to changes in the size and shape of the ocean basins (resulting either from the formation of new oceanic crust, notably as submarine plateaux, or from the replacement of a few large ocean basins by a number of smaller ones). During periods of global warming, some sea-level rise is attributable to expansion of the ocean water; however, an increase of 10C throughout the water column in all oceans would lead to a sea-level rise of only ~10m 8. Global warming during the cretaceous may have been related to the addition to the atmosphere of huge amounts of CO2 as a result of volcanism (as flood basalts and as a consequence of increased rates of sea-floor spreading). However, the warming was counteracted by the removal of atmospheric CO2 through deposition and preservation of carbon in the ocean.
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