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.
The low viscosity of the magma allows the lava to travel down slope on a gentle slope, but as it cools and its viscosity increases, its thickness builds up on the lower slopes giving a somewhat steeper lower slope. Most shield volcanoes have a roughly circular or oval shape in map view.