The National Park Service is cautioning people to heed safety precautions while watching volcanic activity since the latest eruption of Hawaii's Kilauea volcano.

What had been low-level lava flows since Thursday morning became more vigorous fountaining Friday evening, according to the U.S. Geological Survey’s Hawaii Volcano Observatory.

Molten rock began shooting from the volcano before dawn on Monday when fissures opened in the caldera floor and propelled lava 295 feet (90 meters) into the air. The red liquid formed tall fountains and then spread across 650 acres (263 hectares). The Hawaiian Volcano Observatory estimated the lava was about 1 yard (1 meter) thick.