Tsunamis should not be confused with storm surges, which are domes of water that rise underearth hurricanes or cyclones and cause extensive coastal flooding when the storms reach land. Storm surges are particularly devastating if they occur at high tide. A cyclone and accompanying storm surges killed an estimated 500,000 people in Bangladesh in 1970. The tsunami which struck south and southeast Asia in late 2004 killed over 200 thousand people.