The regional government of the Spanish Canary Island of El Hierro has issued a volcanic eruption alert following almost 10,000 small tremors recorded in the past three months. The government posted a yellow alert - second level in a scale of four - Sunday and closed some hillside roads and a tunnel to avoid possible injury by falling rocks. The island's 11,000 residents have been told to monitor communications by the civil protection authority. The island was shaken late Saturday by a 4.3-magnitude quake. Seismic activity began in the area on July 17. Like all the Canary Islands, El Hierro was formed by volcanic activity. It has some 500 volcanic cones.