What does the ancient earthquake detector do? it help tell the direction of where it came from and the slightest movement will make the ball fall if you are referring to the ancient china one Edit
Depending on the type of lava flow, the resulting rocks look very different. This was a pahoehoe flow. A lava flow is caused by a volcanic eruption. The lava can flow down the volcano at speeds ranging from 1/24 to 50 meters an hour. They can be 1,300 degrees fahrenheit or more. They are very destructive.
Shield Volcanoes. Because mafic lava is low viscosity, when it erupts from a volcano it flows downslope away from the vent, gradually cooling and crystallizing. Because of the relative ease of flow, basaltic volcanoes are broad, with gentle slopes. They don't have the stereotypical steep volcanic cone shape.