Puerto Rico lies at the boundary between the Caribbean and North American plates. This means that it is currently being deformed by the tectonic stresses caused by the interaction of these plates. These stresses may cause earthquakes and tsunamis. These seismic events, along with landslides, represent some of the most dangerous geologic hazards in the island and in the northeastern Caribbean. The largest, most recent major earthquake occurred on October 11, 1918 and had an estimated magnitude of 7.5 on the Richter scale. It originated off the coast of Aguadilla and was accompanied by a tsunami. On September 24th, 2019 an earthquake over 6.0 was recorded 49 miles off the island's northwest coast at a shallow depth of 6 miles. It was recorded by the United States Geological Survey (USGS) organization.