On December 26, 2004, a 1300-km (800-mi) length of sea-floor boundary between two tectonic plates ruptured in the Sumatra-Andaman earthquake. This earthquake was one of the five largest earthquakes of the past 100 years and the largest since 1964. Sea-floor deflection from this massive earthquake created one of the largest and most far-reaching tsunamis observed by humans. Estimated deaths along the coastlines of Indian Ocean nations approached 300,000, marking this as one of the most lethal natural disasters in human history.