Click on the link above to see what a volcano looks like after she's blown her top. This is the famed tourist destination, Santorini. Many people fail to realize that this is also the sight of a massive eruption that sent an ash cloud and tsunami across the water to Crete, thus destroying the culture and civilization there. This happened during ancient times. Something like this could very well happen again, as in the case of any massive landslide on Gran Canary Island, off of the North African coast. The volcano on that island split after a large and recent earthquake, and if the side of the volcano were to slip into the ocean, it could cause a tsunami large enough to cause massive damage to cities like New York. It's always good to be aware of these risks when choosing to live near the coast. Know the lay of the land, and the quickest routes to higher ground, if you do indeed live or work near the coast. Our planet is dynamic and always changing, and humankind is a small dot in comparison.