22

The Cascade Mountain Range in the US Pacific Northwest is a good example to use to explain this. The predominant wind direction is from the West - over the Pacific Ocean. The air over the ocean picks up moisture from evaporation. After it passes the coast, the mountains cause the air to rise. As it does so it cools. Colder air can hold less water vapour than ...


10

A few elements to complement @Siv answer, and some alternatives hypotheses: Originally the idea was that the Fe2+ oxidation into Fe3+ that lead to the formation of the BIF ("banded iron formations") was an indirect consequence of the increased atmospheric pO2 caused by the photosynthetic activity of, then freshly appeared, cyanobacteria (see e. g. Cloud ...


9

While this does not directly answer the question, these two ideas are relevant: Rare Earth hypothesis and Mediocrity principle. More focused to the question, This letter to nature discusses the purposed link between evolution/mutation rate during of life and magnetic pole reversal periods. You see, when the magnetic fields reversed, it widely thought that ...


9

One possible key is isotopic fractionation via biological processes - see dating the development of the C4 photosynthetic pathway, and specifically isotopic fractionation between carbon-13 and carbon-14. δ13C from volcanic degassing is markedly different to that from biological sources; the arguments for human involvement in climate change (see e.g. ...


8

As you say, the existence of organism that live out of chemical compounds expelled by hydrothermal vents (Chemoautotrophs), immediately render the sentence "All life on earth gets its energy from the sun" as an approximation. However, some approximations are pretty good for all practical purposes. Nevertheless, this approximation (even if right), have some ...


8

You are correct in thinking that oxygen comes from photosynthesis. In fact it is so much associated with photosynthesis, as opposed to any inorganic process, that the presence of oxygen in the atmospheric spectrum of other planets (solar or exoplanets) is reckoned to be one of the best indicators of life beyond Earth - not that such oxygen has been ...


8

I'll augment the other answer with an example. Consider a theoretical north-south oriented mountain range that rises 2000 m above sea level and the land on either side of the range is at sea level. A little ways west of the mountain is ocean. The location is the mid-latitudes and the prevailing wind is from the west. Air along the surface travels above ...


8

The phosphorous sinks are the ocean and ocean sediments. The ocean holds $3 \times 10^{15}$ moles of phosphorous. The annual amount of phosphorous input into the ocean, as well as the amount of burial of phosphorous as sediment is on the order of $10^{10}$ moles. The sediment is of three categories: Phosphorous associated with calcium carbonate ...


8

This is only a partial answer as it doesn't explain why the excess of O2 stayed but one thing you have to appreciate is the fact that aerobic respiration appeared almost half a billion years after photosynthesis, so we can't really say that photosynthesis and respiration have always balanced each other. Cyanobacteria (and with them photosynthesis) are ...


7

As far as I know there are no extinction phases that have been connected to a magnetic reversal. From this one can argue that there is no or only minor changes in the amount of radiation that reaches the Earth's surface. Life in the oceans and underwater anyway has an extra protective layer, i.e. water (but also see this as a grain of salt because most ...


6

At μ/g level some decade ago, they were explained as forming in relation to the oxygenation of the atmosphere, as photosynthetic life developed changing a reducing environment to an oxygenated one, iron oxides formed precipitating out of seawater in variable bands related to local (or possibly seasonal) oxygen availability. Though this traditional ...


5

There are no perpetual motion machines. So when you think you've found one, you need to ask a couple of questions, because there will always be an answer to at least one of them. How is the dissipation of energy being concealed? That is to say, some energy store is being depleted - where is it? Where is the additional energy coming from? In this case, ...


5

After some more research, the conclusion is that aragonite is somewhere between 10 and 50% of total CaCO3 production: Aragonite, calcite-Mg and calcite are the 3 main species of marine CaCO3. Aragonite is unlikely to be a major component of the total CaCO3 flux (Berelson, 2007), though the exact contribution is uncertain and falls in the range of 10-50% of ...


4

A non-conclusive list: frequent wildfires not enough water too much water bad soil conditions average temperatures too high or low not enough sunlight animals human intervention other vegetation is better adapted to local conditions and thus suppress growing trees


4

Coral die because of coral bleaching, a process in which the symbiotic algae living in the coral (which give the coral its colour), leave the coral host. Bleaching can occur for a variety of reasons, but the ones that relate to a warming climate are: Ocean acidification caused by dissolution of carbon dioxide in the water. Thermal stress. According to this ...


3

From what I've read so far, it appears jarosite may not be a prerequisite for the formation of certain life forms, instead that it is produced by certain organisms. Río Tinto (Huelva, southwestern Spain) is an extreme environment with a remarkably constant acidic pH and a high concentration of heavy metals, conditions generated by the metabolic activity ...


3

First thing is that the sea-level wasn't necessarily that high when the reef was growing, Hondurus is on the edge of the Caymen Trough Fault Zone and experiences quite high rates of uplift, (relatively speaking, your fingernails actually grow faster but over long periods it builds up). So the Coral reefs you're seeing high and dry could be quite recent in ...


3

It is very likely that there will always be phosphorous for mining, because rising demand will increase prizes, and make more mining sites profitable (This is like the golden rule of mining and seen for example with oil sands suddenly being profitable). From a crystalline-rock perspective (this is just a partial answer) the phosphate minerals are a huge ...


3

Depends upon the species. If the pollen spores are large enough, and of wide spatial distribution, and easily recognizable, and preserves well in sediments, and of distinctive age range (geologically), then it could be used. There have been mistakes in the past where modern pollen collected in microscopic pores in older rock, giving the illusion of rock ...


3

A weed is just a plant where you do not want it. Totally a matter of context. Tumbleweeds are non-native, introduced centuries ago. I assume you mean the invasive species of plants that have been spread by humans and are disrupting ecologies throughout most of the world Until recently, these plants we consider weeds were limited in their range to home ...


2

In addition to what @GordonStanger said, there are a few other points to consider. Pollens and spores are made out of sporopollenin which preserves way better than what one would expect. Although there isn't probably a perfect 1-to-1 correspondance between pollen morphospecies and the plant species that produced them, there is still a wide variety of pollen ...


2

My answer goes a little beyond the evidence -- there isn't much evidence. The question There's a lot of free oxygen now. This oxygen did not suddenly come from underground or from space. So it used to be attached to something. The question is, what was it attached to, and what happened to what it was attached to? Background First off, there's every ...


2

The pH of ocean water is currently about 8.1, which lies between the second and third dissociation constants (7.20 and 12.37, respectively). So most of the phosphate inthe ocean in its twice-dissociared form, as $\text {HPO}_4^{2-}$. For comparison, our own blood is around pH 7.4, so phosphate in our blood would be a mixture of $\text {HPO}_4^{2-}$ and $\...


2

I think you are correct. Typical sand is silica (white) with a little Fe2O3 (red) to give a "sand" color. FeO is black and over geological time in air, oxidizes further to Fe3O4 with hydroxides and hydrates (black and dark brown) and eventually Fe2O3.


1

If the crust were the thickest layer or Earth, several things would happen: It wouldn't be a "crust" any more, by definition. Because this is what a "crust" is: a thin layer on the exterior of something. However, if we assume that the mechanical properties of the crust (being cold and brittle etc) would extend deeper in the Earth, the following applies. No ...


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