Nina investigates what volcanoes are - with the help of Luke, her sight neuron and Belle, her hearing neuron. Explorers Lily and Rebekah visit Nina in her workshop and discover that volcanoes erupt and hot, red liquid called lava comes out and makes the volcano a cone shape. Next they visit a metal works and see very, very hot metal which looks just like lava. Last, they make their own volcano and find out that lava pushes up out of the volcano because it has bubbles in it that are trying to get out.
