Soru

### Snowball Earth Deglaciation Debate

During the Cryogenian period (approximately $720$ to $635$ million years ago), Earth experienced global-scale glaciations during which ice sheets extended to or near the equator. Three hypotheses discuss the primary trigger and conditions that initiated the rapid deglaciation (melting) of these global ice sheets.

Hypothesis 1
During the global glaciation, the surface of the Earth was completely sealed by ice, which temporarily halted the hydrological cycle and stopped all chemical weathering of continental rocks. Over millions of years, volcanic activity continuously released carbon dioxide ($CO_2$) into the atmosphere. Because there was no liquid water or exposed rock to absorb it, $CO_2$ accumulated to extremely high levels (nearly $350$ times modern levels). This massive greenhouse effect eventually warmed the planet enough to initiate melting at the equator. Once initiated, the ice-albedo feedback caused the entire global ice sheet to melt extremely rapidly (in under $10,000$ years), transitioning Earth into an ultra-greenhouse state.

Hypothesis 2
The glaciation was not complete; localized areas of open ocean existed near the equator, allowing a minimal hydrological cycle to persist. Deglaciation was primarily triggered by orbital variations that increased solar radiation at low-to-mid latitudes, combined with the accumulation of dark volcanic dust on the ice surface. This dust reduced the ice's albedo (reflectivity), absorbing more solar energy and initiating melting. Although volcanic outgassing of $CO_2$ occurred throughout the glaciation, chemical weathering of rocks on ice-free nunataks continued at low rates. The warming from solar radiation and dust-induced melting was rapid, taking less than $12,000$ years to melt the ice sheets, and was only subsequently reinforced by rising greenhouse gas levels.

Hypothesis 3
Global ice sheets covered the continents and most of the oceans, preventing chemical weathering of continental rocks due to the lack of exposed land and liquid water runoff. The sudden trigger for deglaciation was the destabilization of massive deposits of methane hydrates (clathrates) in shallow marine sediments. Geothermal heat accumulation beneath the thick ice sheets caused these hydrates to dissociate, releasing vast quantities of methane ($CH_4$)—a greenhouse gas much more potent than $CO_2$���into the atmosphere. This release caused immediate, catastrophic global warming. Once melting began, the ice sheets collapsed and melted in less than $5,000$ years.

Instruction: Match each scientific claim with the specific hypothesis or combination of hypotheses that agree with the claim.