To be sure, the American Mastodon is a worrywart. You would be, too, if you spent most of your waking life fleeing scantily clad indigenous people and their pathetically constructed wobbly wooden spears. However, his worries tend to be of the personal and private matters, like whether or not that salve is working on that open wound on his foot. On the other hand, the Mastodon's older brother, the Wooly Mammoth, is a mammal to whom the words, "just relax" don't apply. His worries tend to originate from larger, more cataclysmic concerns. E.g., the possibilies of a nuclear holocaust, a city-razing earthquake, an Ebola outbreak, or the invasion of the Russkies a la Red Dawn are all more likely to keep him from sound sleep.
Therefore, he is undoubtedly twittering the night away in worry of the possibility of not one, but two mega-tsunamis in the near future: an imminent Hawaiian volcanic eruption, sending a topshelf into the Pacific and wiping out the western American coast, or, more dire still, the combo of a North Korean atom bomb being detonated for the purpose of the world's largest mega-tsunami - those bastards are trying to send a whole mountain into the ocean! It'll kill everyone!!