Iceland raised the alarm after its largest volcano was hit by the biggest tremors since 1977. Two quakes larger than 4 in magnitude early Monday rocked the crater of Katla, the country's Met Office said in a statement. That was followed by at least 10 more tremors at the volcano, which rises 1,450 meters (4,757 feet) into the air on the North Atlantic island's southern coast. There were no immediate reports of casualties or damages to property. Katla last erupted in 1955 and 1999. Neither of those were large enough to break the ice covering its 10 kilometer-wide (6 mile) caldera. Its last major eruption was back in 1918, when it spewed ash for more than five weeks. An eruption of the Eyjafjallajokull volcano in 2010 caused the cancellation of more than 100,000 flights across Europe on concern that glass-like particles formed from lava might melt in aircraft engines and clog turbines. Historically, Eyjafjallajokull has been known to erupt one to two years prior to Katla. A magnitude 6.2 quake killed at least 250 people in central Italy last week.