A mandatory evacuation order was issued Thursday night for a portion of the Leilani Estates subdivision as "vigorous lava eruptions" threaten more homes, the Hawaii County Civil Defense Agency said.Residents have been advised to evacuate by noon Friday. Emergency responders have no plans to rescue anyone from the evacuated areas past the deadline, the agency said."They are being asked to leave. Period," county spokeswoman Janet Snyder told reporters.Those in Kapoho — including Kapoho Beach Lots and Vacationland — also were ordered out due to the risk of getting trapped by the lava. Four weeks have passed since the first eruption rocked Hawaii's Big Island and lava continues oozing from volcanic fissures, burning homes to the ground and turning into rivers of molten rock.The US Geological Survey said the lava from the Kilauea volcano has covered an area of 5.5 square miles — that's four times as big as New York's Central Park.Fissure 8 remains the most active, the USGS says, sending "persistent fountains" of lava as high as 260 feet into the air. Lava lobes from Fissure 8 were advancing 100 yards an hour, the USGS said. "This is the hottest lava we've seen during this eruption," Wendy Stovall, a scientist with USGS told CNN affiliate Hawaii News Now. "Lava can't get hotter than where we are."Besides the lava, there's also the danger of "vog," or volcanic smog. Vog is a haze created when sulfur dioxide gas and other volcanic pollutants mix with moisture and dust.In addition to volcanic particles that can cause eye, skin and respiratory irritation, residents were warned to be on the lookout for sharp, thin strands of volcanic glass fibers known as "Pele's hair," a reference to the Hawaiian goddess of fire. The Civil Defense Agency warned it could cause injury if it got in residents' eyes or was breathed in.
CNN's Joe Sutton and Dakin Andone contributed to this report.