Volcanoes are usually formed through the movement of tectonic plates and the build-up of pressure from convection currents - heat inside the earth - usually in the form of magma. Some volcanoes can form in places other than tectonic plate boundaries. These are known as hot spots.
When the magma bursts through the surface, it cools and hardens. Ash might also settle on top of this volcanic rock. This process continues to build up the sides of the volcano. Magma, rocks, gases and steam from the Earth's centre are emitted through volcanoes.
Volcanic activity can either be intrusive or extrusive. Intrusive volcanic activity results in magma making its way up to the crust, where it cools down and solidifies into volcanic rocks. Extrusive volcanism occurs when magma bursts through the Earth's crust.
The eruption of the volcano that remains as Table Top Mountain created what you see now. Below the ground molten rock or magma rose to the surface boiling all the nearby groundwater. The build up of pressure resulted in a violent explosion. The settling debris formed a crater of tuff (loose rocks in volcanic ash). Magma filled the crater and overflowed as lava. The cooled, solidified lava formed basalt.
Now for your assignment to log this cache... as always, do NOT post answers in your logs. Logs with answers will be deleted. Please e-mail me the answers to these questions, and the names of any cachers in your group. If I don't receive answers within seven days, logs will be deleted. I don't like doing it, but it is part of the game, so please comply.
1. How many years ago did the eruption occur?
2. Table Top is renowned for a particular feature that the basalt rocks have formed. Name this feature.
3. Do you think this volcano is extinct? What evidence could you look for?
4. (Optional) Post a photo without any spoilers, thanks.
FTF goes to Geo~Gypsies