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.
If the lava has low viscosity then the molten material will act fluidly and flow fast down the volcano flanks. As lava travels down the volcano sides, the surface of the flow will cool much more rapidly. The surface of the flow forms two different types called 'aa' and 'pahoehoe'. Aa lava (pronounced ah-ah) has a rough, jagged surface due to the gas explosions tearing apart the external crust. It looks like a pile of blocks and rock fragments but underneath lies molten lava. As the lava flow advances it is churned and folded over itself, allowing gas to escape.