I always thought this meant that ISIS would detonate the side of a western facing mountain/volcano in the Canary Is triggering a US east coast tsunami.
https://en.wikipedia.org/wiki/Megatsunami
La Palma is currently the most volcanically active island in the Canary Islands Archipelago. It is likely that several eruptions would be required before failure would occur on Cumbre Vieja.[20][21] However, the western half of the volcano has an approximate volume of 500 cubic kilometres (120 cu mi) and an estimated mass of 1.5 trillion metric tons (1.7×1012 short tons). If it were to catastrophically slide into the ocean, it could generate a wave with an initial height of about 1,000 metres (3,300 ft) at the island, and a likely height of around 50 metres (164 ft) at the Caribbean and the Eastern North American seaboard when it runs ashore eight or more hours later. Tens of millions of lives could be lost in the cities and/or towns of St. John’s, Boston, Halifax, New York, Baltimore, Washington, D.C., Miami, Havana and the rest of the Eastern Coasts of the United States and Canada, as well many other cities on the Atlantic coast in Europe, South America and Africa.[20][21] The likelihood of this happening is a matter of vigorous debate.[23]