“No, Mother Earth is not fixed, but continually changing, both inside and out. There are tremendous fires on the interior and these often crack open the dirt and rock, letting in large quantities of sea-water. Then comes an explosion, just as you may have at home if you throw cold water into a red-hot kitchen range. The steam and gases don’t know where to go, and consequently there is a volcanic eruption, or else something breaks loose underground and an earthquake follows. If this happens close to the sea, or under the sea, there is a tidal wave, the water going down and up with the movements of the ocean bed.” “Do all earthquakes come from volcanic fires?” asked Sam. “We cannot answer that, Samuel. Some earthquakes seem not to have any connection with volcanoes, as for instance the earthquake at Charleston, South Carolina, in 1886. There was no fire there, and but little gas, and what caused the quaking, with its tremendous damage to property and human life, is a mystery.” “What was the very worst earthquake known?” came from Frank. “That at Lisbon, Portugal, in 1755. It happened late in the year, and before it occurred there were numerous small earthquakes and volcanic outbursts throughout Europe. When the big earthquake came there were three shocks in quick succession and the very bottom of the harbor dropped out. After many ships were engulfed, the bottom of the harbor came up again and there was a fierce onrush of water. What was left standing of the city took fire, and fully fifty thousand people lost their lives.” “Isn’t Vesuvius the largest of all known volcanoes?” asked Darry.