Siljan Ring Siljan Ring The Siljan Ring () is a prehistoric impact crater in Dalarna, central Sweden. It is one of the 15 largest known impact craters on Earth and the largest in Europe, with a diameter of about . The impact that created the Siljan Ring occurred when a meteorite collided with the Earth's surface during the Devonian period, about 376.8 ± 1.7 Ma. This coincides around the first Devonian extinction, the Kellwasser Event or Late Frasnian extinction at 376.1 Ma ± 1.6 Ma. The effects of the impact can clearly be seen in the bedrock in the area. The Cambrian,
Mora (canton) eastern border. The canton of Mora is subdivided into six districts ("distritos"): The canton of Pacaca was established by a decree of May 25, 1883. Three years later, the canton's name was changed to Mora in honor of Juan Rafael Mora Porras (1814-1860), the second President of Costa Rica. Mora (canton) Mora is the 7th canton in the province of San José in Costa Rica. The canton covers an area of 162.04 km², and has a population of 23,004. The capital city of the canton is Ciudad Colón. The Río Virilla establishes the northern boundary of the canton, with the