Soru

### Models of Snowball Earth Initiation

Geological evidence suggests that during the Neoproterozoic era, Earth experienced global glaciations where ice sheets reached the equator (the "Snowball Earth" hypothesis). Two models propose different mechanisms for how this extreme cooling was initiated.

Model 1 (Volcanic Aerosol Albedo)
This model proposes that a series of massive, low-latitude volcanic eruptions released vast quantities of sulfur dioxide ($SO_2$) gas into the stratosphere. In the stratosphere, $SO_2$ reacted with water vapor to form highly reflective sulfate aerosols. These aerosols remained suspended for years, reflecting incoming solar radiation back into space. The resulting surface cooling initiated the expansion of polar ice caps. Because ice has a high albedo (reflectivity), the expanding ice reflected even more sunlight, creating a runaway ice-albedo feedback loop that rapidly froze the entire planet. The primary driver was thus the reduction in absorbed solar energy due to stratospheric aerosols.

Model 2 (Silicate Weathering Drawdown)
This model proposes that the breakup of the supercontinent Rodinia, which was positioned near the equator, initiated global glaciation. Because the continents were in a warm, wet equatorial region, weathering of silicate rocks occurred at extremely high rates. The chemical weathering of silicate rocks removes carbon dioxide ($CO_2$) from the atmosphere and sequesters it in ocean sediments. The rapid continental breakup also increased runoff, accelerating this process. The depletion of atmospheric $CO_2$ weakened the greenhouse effect, causing global temperatures to plummet. Once temperatures dropped sufficiently, polar ice caps began to expand, initiating the ice-albedo feedback loop. The primary driver was thus the reduction in atmospheric greenhouse gas concentrations.

Based on the descriptions of Model 1 and Model 2, match each statement about the initiation of Snowball Earth to the model or models it represents.