Aerosol is a word that many people are familiar with. In many countries some items described commonly as aerosols have been banned as they themselves emit what is really the aerosol. The most technical definition of an aerosol is very similar to that of colloid, a suspension of particles in a fluid (normally air). Aerosols are notorious for their ability to rise into the upper atmosphere and interfere with incoming light from the Sun. It is for this reason, as well as chemical reasons related to chlorine’s catalytic abilities, that some man made aerosols have been made illegal. Of course not all of these particles necessarily have to come from a human source and even if they do they can be more advanced than simple molecules. Organic aerosols have their role to play as well with a great number of aerosols falling into the organic category.
The El Niño southern oscillation is a an oscillation in wind and seas surface temperatures of the Pacific Ocean. The ups and downs of temperature come in intervals although they are highly sporadic and so the periods can be quite irregular with random amplitudes when it comes the to the temperature peaks and troughs. The warm sections are given the name El Niño and the cold sections, La Niña, literally meaning the boy and the girl if my Spanish hasn’t failed me. Both periods typically last only a couple of months each being split by periods just known as neutral with no major temperature fluctuations. It is widely accepted that this oscillation is caused by a positive feedback loop called the Bjerknes loop where a rise in sea surface temperature in the central pacific weakens the easterly wind which in turn lets more warm water disperse east which leads to more warm water being brought up from the deeper sea which all together raises the temperature of the central pacific and so on.
Although radioactive dating is often talked about another, no less important type of dating, luminescence dating, is not. Luminescence dating is used to study the last time a piece of rock was in the sunlight. It can only be used on materials seen as semiconductors, mainly quartz and feldspar as these both contain silicon, but if the date these rocks were buried is known then the date of the surroundings is also known. The dating works by looking at the number of trapped electrons present in the rock. You see crystal lattices can develop defects which in this case are called electron traps. As various radioactive decays occur in the rocks around them the ionising radiation produces electron-hole pairs within the lattice. The holes exist in the valence band and electrons exist in the conduction band and these electrons also can get trapped in the interband region caused by the defect. These electrons can then be released when light is shone upon the rock and so we can learn how long it has been in the ground based on the amount of charged stored within it.
The basic process which occurs in every power plant is quite simple: heat is produced from fuel, this heat boils water, that water turns a turbine connected to a generator producing electricity. Every day 161 billion gallons of freshwater is pumped to fossil fuel power stations in the US and most of this actually goes straight to condensing the already boiled water. In thermodynamics it is favourable to always transfer temperature the hottest and coldest thing possible as this has the most energy efficiency output of work. The Environmental Protection Agency (EPA) in the US also puts an upper limit on the temperature of waste water released from facilities in order to protect aquatic environments. All of these become major concerns when there is not enough water to supply the plant and absorb all the heat being given off.
Nuclear weapon testing has been both a good and a bad thing for the study of radioactive dating. On one hand the nuclear material released into the atmosphere has made it more difficult to accurately determine ages as the released radioactive material alters the naturally present concentrations in the atmosphere. On the other hand it can actually be beneficial in cases such as limnology. If some freshwater is found checking the radioisotopes present will reveal whether it has been recycled during the nuclear age. Another good example is to use the great increase in unnatural radioisotopes produced during a nuclear detonation, caesium-137 for instance, to calibrate other dating techniques. Since we know the exact dates of these explosions we can find the soil layer containing large amounts of caesium and check other dates compare to it.
It is a common concern of the day that the world is running out of oil. Although partly this worry is caused by the oil producing countries not wishing to overextract oil as this would significantly lower the price and therefore the income they rely on there are still genuine supply concerns out there. Petroleum reservoirs are subterranean pits full of crude oil and are considered the most common source of our oil. It is can be considered worrying, therefore, when we can only extract 30% of the oil contained on average from any give reservoir. Apparently an extraction of just 50% or 60% is considered exceptionally lucky. To aid this, new technology is constantly being developed to assist the oil industry in their extraction plans.
Rivers almost always lead to the sea (they can also lead to evaporation planes, in fact, every river in Uzbekistan does this) and in doing so they follow a very distinct geometry which can be aptly described as a branching network. It is through these networks that water flows and carries with it sediment and debris and it through this action that rivers evolve and change the landscape around them.