I've been like this about most of my special interests (though my interests in education, the brain, and learning disabilities have continued since childhood and high school, respectively, and hopefully they'll last for life). For example, I obsessively followed the news using publications of every political viewpoint in high school, and now I can't bear to hear, see, or read anything about politics. I agree with dyingofpoetry, there's no way I would be like this about disasters. It would be overwhelming emotionally as well as sensorily.
The way I explain it is, my brain is chronically understimulated (thank you ADD) and yet demands an absurd level of intellectual stimulation because it's wired to process a lot of information at a high level very quickly. (Because of the "use it or lose it" principle, the more information your brain is capable of processing, the more it also demands in order to just tick over). However, it's difficult to give myself that stimulation, because I also have a limited amount of attention and working memory (thank you again, ADD). Special interests are the most efficient way to a) focus that limited amount of attention and working memory, instead of having it be scattered all over the place, b) stimulate my brain, and c) keep my brain working at its optimum level.
Most of all, though, they don't just engage my brain, they engage my emotions like almost nothing else. With my special interests in dinosaurs, prehistoric people, and various animals as a kid, I used to imagine what it was like to BE all of those creatures. My current psychology-related interests have huge implications for how people see themselves, educate their kids, and live their lives, at least in theory. The feeling I get from pursuing special interests is a mix of energy and the most intense happiness imaginable...it's like pure essence of vitality. Csikszentmihalyi refers to the experience as "flow," (although he associates it with more than just special interests), and believes it's one of the keys to happiness. ( Here's a link to the book I'm talking about, because it's amazing: http://www.amazon.com/Flow-Psychology-O ... 298&sr=1-1) I totally agree with him about this.