By Louise Rasmussen and Johannes Birkebaek COPENHAGEN (Reuters) – Icelanders are working round-the-clock to build dykes the size of three-storey buildings to protect a vital power plant and homes from lava flows, since volcanoes near the capital Reykjavik that were dormant for nearly 800 years became active. The six volcanic systems, which experts forecast will be active for up to three centuries, stretch under Iceland’s southwestern Reykjanes peninsula, home to 30,000 people, nearly 8% of the country’s total population. They form an underground meshwork on the peninsula, stretching to the edg…