There is a theory called the "Snowball Earth" that I think leads to some serious problems for the young earther. Let's take a look, shall we. For decades, it has been recognized that there was evidence of worldwide glaciation in the Neoproterozoic era (ending about 543 million years ago). Glacial deposits have been found nearly worldwide from this time. One difficulty in making the leap to global glaciation was that it needed to be ruled out that the deposits could have been formed when the landmass was far from its current location and that the glacial deposits could be local and due to the land being at high latitude at the time. What was needed were deposits that had convincing data that they were formed at tropical latitudes. In the 1960's, Harland found glacial deposits that showed indication of being formed in the tropics due to the association of the deposits with certain sedimentary strata normally formed at low latitudes. This was a start. "The Great Infra-Cambrian Glaciation," Harland and Rudwick, Scientific American, Vol. 211, No.2, pages 28-36, Feb. 1964. Later, Kirschvink found deposits that were even more convincing. The first step was to test the rocks with a method called natural remnant magnetization (NRM). With NRM, you measure the remnant magnetic field through the deposits in question. If they formed near the poles, the magnetic field lines will tend to run up and down. The lines will become oriented more and more horizontally the closer you get to the equator. You must also make many many measurments of different rocks. What he found was that the sedimentary deposits from the glaciers were formed in the tropics. The other crucial step was to establish that they were formed at sea level. This is important since even today, some glaciers exists at high altitude at low latitude. The deposits were associated with deposits that were tidal in nature and therefore had formed near sea level. "Late Proterozoic Low-Latitude Global Glaciation: The Snowball Earth," Kirschvink, The Proterozoic Biosphere, Cambridge University Press, Cambridge, pages 51-52, 1992. To look at the other evidence for the Snowball Earth, we need to consider what the effects of a global covering in ice would be. With most of the surface water of the earth covered in ice, gas exchange between the ocean and the atmosphere would cease. The ocean would largely become anoxic, that is very low in oxygen. This in turn would change the solubility or iron in the water. Oxidized iron is rather insoluble while reduced iron is more soluble in water. The anoxic water would allow for a buildup of iron in the oceans. When the ice was removed, the sudden influx of oxygen into the oceans would cause the iron to rapidly fall out of solution. And indeed we find that banded iron formations (BIF) from the Neoproterozoic era are associated with the glacial deposits. With the continents covered in ice, the normal mechanisms for removing CO2 from the atmosphere would stop. Typically, small amounts of CO2 are dissolved in rainwater. This reacts with the rocks of the continents and geologically locks up the CO2. With the rocks covered in ice, the CO2 from geological sources would continue to pour into the atmosphere and build up. During the Snowball Earth, this CO2 built up in the atmosphere until the global warming effect was great enough to melt the ice and send the earth into the hothouse. The level of CO2 calculated to be needed to end the global glaciation is about 12% of the atmosphere. Once this was achieved, rapid warming would melt the ice and cause a rapid warmup in the earth's temperature, much warmer than today even. Estimates of sea surface temperatures are about 120 F. All this atmospheric CO2 would also be rapidly removed from the atmosphere and rapidly deposited over much of the world. And we see just this in the rocks. These worldwide glacial deposits are covered in thick cap dolostones as would be expected if large amounts of CO2 were nbeing removed. These dolostones also preserve another record of the expected warming. The warm waters would drive extreme weather. High levels of rainfall and glacial melt combines with the fractured and groung rocks from the glaciers would lead to rapid erosion of the land. The higher levels of the cap dolostones are mixed with clays. The dolostones also preserve features such as crystal fans and gas escape tubes that indicate formation by precipitation from water saturated with carbonates. There is an even more curious feature of the layers. The CO2 outagssed from volcanoes contains about 1% C13 and the remainder C12. However, plants fix C12 at a higher rate than C13. By looking at the ratio of C12 to C13 in deposits, it is possible to tell how much of the carbon was removed through organic processes and how much through non-organic processes. The ratios just below the glacial deposits show ratios that indicate that about half of the carbon deposited was from organic sources. (Today that number is about 25%.) But in the glacial deposits and the cap dolostones, the ratio changes to essentially that of the volcanic gasses showing that the carbon being removed was almost all through non-organic processes. The ratios then return to normal. This is to be expected. With the earth covered in ice, biological activity would decrease tremendously. Once the ice started to melt, even though biology would be expected to take off in the warm waters, the rapid geological processes would have swamped any biological effects. One of the strongest oppositions to the theory came from biology. Just how could life that required photosynthesis have survived the Snowball. Recently life has been found under thick layers of ice in the antarctic that gives clues about how life could have survived. Ice in such regions has also been shown to transmit enough light for photosynthesis to much deeper layers that previously thought. Combine this with local oases such as undersea vents, hot springs, and areas of open water and life manages to survive the snowball. "A Neoproterozoic Snowball Earth," Hoffman, Kaufman, Halverson, Schrag, Science, Vol. 281, pages 1342-1346, August 28, 1998. The Snowball Earth theory seems to be the only one that can explain the tropical glacial deposits, the cap dolostones, the paradox having these two close by implies (extreme cold followed by extreme warmth), the associated BIF, and the excursions of the carbon isotopes through this period. The obvious answer for YEers is to invoke the flood. But this has several problems. How does a flood result in glacial deposits? How does a flood result in such thich caps of carbonates? (Where did all the CO2 come from?) How do you make the ocean anoxic in order to dissolve all that iron with the oceans and atmosphere in continuous contact and exchange? If the oceans were anoxic, how did the fish survive? How are the carbon isotope anomolies explained? Provided that reasonable solutions can be reached for all of those, there remain two more. First is that there are at least four such events recorded worldwide. How do you work all of these into one event? Second, life on the surface could not survive 12% of the atmosphere as CO2. Respiration would be impossible. Your lungs would be unable to discharge waste gas from your lungs. Just not enough driving force to get the gasses out of the blood by overcoming the partial pressure.