Hashtags for such situations also provide a way for the public to express their sentiment — something many of us feel compelled to do in the case of a disaster. When it comes to natural disasters, a hashtag is like an information lifeline. We cling to it, to learn more about the event and provide an emotional outlet. Trends are determined by an algorithm and, by default, are tailored for you based on who you follow, your interests, and your location. This algorithm identifies topics that are popular now,.