Glaciation is one of the issues science wrestles over, now more now than ever before. Aside from the nature and existence of “trace” there may indeed be an issue of murder if global warming is due to the industrialization of civilization because if it changes growing patterns of ag crops, vector vulnerability, and animal abundance enough, people will die of famine and climate disasters. Let’s begin way before such issues, at a time when there was no life: “Snowball earth”, a phrase that refers to the planet being totally frozen (even the oceans) or partially glaciated, which happened repeatedly to different degrees.
Most people think of geology as the land they can see rather than the interactions of air, water, and deep earth patterns like aquifers, molten upwellings, the jet stream and whatever the hell frakking is doing as it multiplies small earthquakes.
Relying on wikipedia (is there life on wikipedia?), these approaches offer theories.
Change in the chemical makeup of the atmosphere.
Change in the chemical makeup of the atmosphere.
“The geological time frames under consideration come before the sudden appearance of multicellular life forms on Earth known as the Cambrian explosion, and the most recent snowball episode may have triggered the evolution of multi-cellular life on Earth. Another, much earlier and longer, snowball episode, the Huronian glaciation, which occurred 2400 to 2100 Mya may have been triggered by the first appearance of oxygen in the atmosphere, the "Great Oxygenation Event."
It’s a sequence: methane in the atmosphere created enough of a greenhouse effect for vegetation to flourish, and they made so much oxygen that animals could develop. “The Huronian glaciation followed after the Great Oxygenation Event (GOE), a time when increased atmospheric oxygen decreased atmospheric methane. It is the oldest known ice age, occurring at a time when in biological sense, only simple, unicellular life existed on Earth.” We appear to be reversing this process.
Moving spheres in the layered planet:
The molten core moves according to its temperature. It may be a factor in El Nino. At the outer limits of thin atmosphere and gravity, the penetration of the sun energy varies. In between are, from the inside out (so far as we know) are plate tectonics floating on the molten core. These are huge and moving, so they collide, riding up over each other or scraping sides, and they leave spaces for major upwellings of magma. The continents float on these tectonic plates, with momentous consequences. We’ll come back to the Rocky Mountains, the Ring of Fire, rain shadows, and so on.
Evidence about these forces is shaky because it is so vast and ancient, but satellites have helped to get the “big picture,” even of the steady air currents and the steady water streams that affect our own transportation routes. Some of the ocean streams are driven by temperature and salinity (melting sending in fresh water from ice) so that if the temperature changes enough it could destroy the Japanese current, which would mean that the Pacific Northwest current might stop or move, which would very much alter the mild temps in those states and in Japan. This has happened and was marked by bitter winters and no summer growing season, thus famine. If the Jet Stream which passes over Valier gets wobbly we have Arctic Intrusions, weeks of sub-zero weather. If it moves vertically, we are literally blown away. If it fails to blow across the Rockies, we will have no Chinook warming winds. If it brings a lot of moisture, which then meets north-to-south arctic wind, we are buried in snow. It is the dependability of these geologically controlled features that has made our lives possible.
The effect of the bi-polar magnetic forces of the planet.
We don’t know much about this, but we do know that the poles can swap positions and that the north pole has moved recently. We are overdue for another swap, but none of the previous have been in recorded time. It’s possible that the poles might turn out to be “trans” and to end up with four or eight poles. Now there’s a pole at each end of the axis of the turning earth. No one knows what would happen if they were realigned. The axis tipping back and forth is what makes our earth seasons. What would happen if the earth stopped tipping? Or turning, come to that.
Sedimentary layers left by moving air, water or land.
Little grains of whatever pile up (as in when a glacier makes deposits) are some of the best “trace”, now that we can detect orientation to magnetism, isotopes, and other atomic phenomena. Some of it is plain, like the prairie potholes from ice boulders that melted after being buried up to their “gills” in earth, or from stone boulders moved and then stranded, called “erratics.” (Napi was always offending them so that they chased him.) As the glaciers picked up, ground up, and redeposited particles, they changed the land. One of the most influential of these sequences scraped over a big rock formation constituted of a natural fertilizer and distributed it over the prairie to the south, adding to its fertility. We’ve just about exhausted that fortuitous sedimentation.
One of the most intriguing sedimentations is “space dust” left from constant bombardment.
Technically, the really big ones would be meteorites. And the really, REALLY big ones would be drastic game changers.
All these moving layers and forces change everything. If they didn’t, the entire planet would “eutropify” which is the term for a body of water that is stagnant, no inlet, no outlet. Eventually it will just go dead. “The "Zipper rift" hypothesis proposes two pulses of continental "unzipping" — first, the breakup of the supercontinent Rodinia, forming the proto-Pacific ocean; then the splitting of the continent Baltica from Laurentia, forming the proto-Atlantic — coincided with the glaciated periods. The associated tectonic uplift would form high plateaus, just as the East African Rift is responsible for high topography; this high ground could then host glaciers.”
Even the underground is always moving. There are three alpine lakes on the planet situated over magma so that the carbon dioxide from the molten substance builds up under the water and eventually explodes. Since humans can’t breathe carbon dioxide except by exhaling, anyone close enough will be asphxiated. Hundreds have died this way but it’s very rare. Still, one thinks about Yellowstone with its magma reservoir. Hopefully, it’s blowing off in the geysers.
Geology is replacing theology. A planet that constantly changes is more than a simple earthquake or eruption and certainly far more than any images of powerful humanoids. How we respond will determine salvation or death for many. It would not be exaggerating to say every living species. How we respond will define how we are human, even on the contemporary high prairie, facing into the wind.