Pollution, as most people understand it, is best described as negative changes in the environment because of humans. You know, like black smoke belching from chimneys or sludge from a chemical plant.
Light pollution: Too many city lights to see most of the stars, or the Milky Way, in the bottom photo. Granted the stars and galaxy are pretty to look at, but the "pollution" is helpful for seeing stuff down here and thus only seems to apply to folks like astronomers.
Toxic waste is also pollution, this stuff was in 55 gal drums which were buried. After a while the drums couldn't support the dirt above and collapsed, resulting in a sinkhole filling with the free contents.
This was actually somebody's yard in a neighborhood near Niagara Falls called Love Canal. How toxic sludge came to be in the yard is a saga that began around 1890. A guy called William T. Love wanted to dig a canal between the upper and lower levels of the Niagara River. Since boats can't go over the falls, he figured this would somehow increase commerece in the area. Before the canal could be finished construction was stopped, leaving a pretty good sized hole going nowhere.
Flash forward to the 1940s, a company by the name of Hooker Electrochemical Company bought the incomplete canal to use as a toxic waste dump. After lining it with clay, they started piling up drums full of bad stuff. Until 1953, which was when the hole was full. So they added a layer of clay on top and then planted grass to make a pretty little park. So pretty that the local school board noticed there was enough room to put a school there. They approached Hooker with a proposal to purchase the park and told them why.
Hooker, being your stereotypical evil chemical company, negotiated an inflated price and sold the land as fast as possible without mentioning what was underneath. There was much rejoicing among Hooker executives, high fives and atta boys abounded when they heard the toxic dump wasn't their problem anymore. KIDDING!!
Hooker actually turned them down and explained that kids should not be going to school over a their old toxic waste dump. See it's cool to put a park over the dump because grass and a few trees aren't heavy enough to affect the waste below. If the worst case happens, then toxic waste ruins a park. Buildings, on the other hand, are much heavier and therefore more likely to bring about the worst case scenario, in a school.
Hooker even took board members to the site, drilled bore holes, and showed them a sample of the hazardous materials. The school board must've thought Hooker was lying, didn't understand what a buried toxic waste dump was, or maybe actually liked it because they started putting pressure on local government to take the property for their precious new school.
Now, if we'd been Hooker, we'd of let them go ahead with their plan and seize the land. We'd of said "Fine take our buried toxic dump to build your school, but when acetone starts seeping up out of the ground you'll feel pretty damn stupid." Instead Hooker finally agreed to sell, under two conditions:
To make a long story short, there was left over land after the school was finished and the school board sold it to a developement company. They wanted to build houses on the extra land, which they did. Can you guess what happened next? Twenty years later, toxic sludge started showing up in people's yards and basements, and despite everything Hooker had done to avoid this, people made them out to be the bad guys. Who cares if the school board was stupid enough to force Hooker into giving up their dump for a school? Nevermind that the same board turned around and sold land they knew was polluted to a real estate developer. After seeing Poltergeist, we're not sure whether the developer knew what was up or simply figured toxic waste was better than human remains to build on.
An oil seep is a place where petroleum products literally come up out of the ground, spontaneously. Remember the Beverly Hillbillys, when Jed was shootin' at some food and instead got himself bubblin' crude? It could theoretically happen, and if Jed hadn't tapped that well, sooner or later erosion would've. Therein lies the basic problem with defining pollution as a solely human thing, either way crude oil is a problem for local animal and plant life.
Tephra is technically rock of any size erupted out of a volcano. Since tephra can range in size from less than 2mm to more than 2m, the term itself is a little vague. We've noted that the word tephra best describes pictures like Redoubt Volcano erupting in our comparison up there. That's because there are chunks of rock in that cloud as big as a one ton human shut in and his/her house, which isn't exactly what we'd call particulate matter. (Galactus would though, size really is relative.)
Fly ash is, well, what's left over after burning coal in that "clean" way they touted so much. The exhaust is filtered through water, kinda like a bong, to remove pollutants and ash. This does cut down on the amount of dirty black smoke given off during the combustion of coal, by a lot. However it shares another trait in common with your standard bong, the water gets dirty and nasty. Now, since it turns out this shit has some legit uses, you'd think "clean coal" is awesome. It would be, except for other problems and the fact that they usually just fill up lake sized holes with the stuff. Which, while less than ideal, also works in keeping the ash from going everywhere. Unless the earthen dam holding the ashy water breaks of course, then things start looking like it would've been better to have not filtered it in the first place.
A fossil reactor is what used to be a natural nuclear reactor. You read that right, natural nuclear reactor. The picture in our graphic is one of the Oklo reactors. About 1.7 billion years ago in what would eventually become Africa, nature was smashing atoms, making plutonium and creating nuclear waste. This was back when life on Earth would've considered oxygen to be a deadly form of pollution, if they had more than one cell of course. So next time somebody says that plutonium and nuclear waste are man made, you'll know they are wrong and will be able to call them on it with the word Oklo.
A lahar, pronounced la-har, is what geologists call mudflows caused by the eruption of a volcano. The one in our graphic happened after Mt. St. Helens erupted in 1980. Before it fell apart and exploded the mountain had glaciers which became mud. Here's some of it is clogging the South Fork Toutle River over six months after the eruption.