Some things to think about in regards to the dreams that you are having. I am not saying that none of you are having prophetic dreams, it is possible, but before reading too much into a dream there are things to consider.
1. Volcano dreams = Something or someone has angered you but you try to repress the anger. You may think that you are over it because you are not AS angry, but it may still be needling you; you replay the offensive situation over and over in your mind. A dream about a volcano erupting is warning you that you are about to "erupt" if you continue to dwell on this. It can also indicate that you feel like you have a lot of pressure you are dealing with and that if something doesn't change soon you could blow up.
2. Lava/fire dreams = Similar to the volcano dreams in that you are feeling "the heat" of something that is occuring in your waking life. Is someone or something making you feel "hot under the collar" or "burns your ass" or any of the other phrases used to describe something that upsets you? You need to deal with those people or issues in order to relieve the pressure and "cool off" as it were.
3. Flood/Tsunami dreams = Water refers to emotions so dreams in which you are experiencing floods, tsumani's, or any other kind of water that can be described as "violent" is telling you that your emotions are overwhelming you. If you have a dream about drowning it is likely telling you that you are drowning in emotions...i.e. are you the type to get weepy, fearful, or extremely sad at the drop of a hat? That is what is causing your dreams of water.
4. UFO dreams = This one is often experienced when you are dealing with something unexpected or unfamiliar, or you have a great fear of the unknown.
5. Attack/War dreams = These are usually the result of feeling like you are being attacked by someone else. Does your spouse, boss, family, grocery store cashier, etc make you feel inferior or treat you like you are stupid? You may not conscious associate these things with being attacked but you are, whether you realize it or not. Often times in your dream you feel like you are fighting for your life and in some ways you are.
6. Prisoner/Trapped dreams = Do you feel that you are trapped in your circumstances and there is no escape. Whether it be a job, finances, relationship, or what-have-you, you will often have dreams about being a prisoner or being trapped somewhere.
7. OR...you just dwell on/think about these kinds of things so much that your fear of these things happening are spilling over into your dreams and thus, creating more fear and drama as you aren't even able to escape it when you are asleep.
These are just a few of the symbolic meanings of the dreams that we have about situations we are dealing with in our everyday lives. They are by no means exhaustive and there may be other things than what is listed above that is the basis for your dreams. Once you can break down the dreams, take out the extra "fluff" that is present, then 99% of the time you can see how your dreams are mimicking your current situations and then figure out how to deal with those issues.
Also...other people in your dreams are often different aspects of yourself and not necessarily the person you are seeing. Their actions, words, etc, are often things about yourself that you may not realize you do and say and that is being shown to you in a form that you can relate to.
Again, some dreams may be prophetic in nature but those are very rare. More than likely the reason people are having dreams of "DOOM" is because they are spending sooooooo much time on websites that deal with doom, watching the news, reading the paper, etc that their dreams are coming up as doomish.