Changes can appear in a variety of forms. There are creeping changes: everything seems to take its usual unchanged course - we are in constant contact with people who are familiar to us and perceive them - and yet we do not perceive that we are changing: there are signs of age, the body changes or our movements. It takes an occasion, a nudge, to realize: hmm, something is different. And then there are upheavals, that we notice very abruptly and immediately: A storm devastates a settlement or a forest, a flood sweeps everything away and leaves damages.