Frequently Asked Questions: Earth Movements

Q. Which workers are most exposed to radioactivity?
A. The workers most exposed to radioactivity in Australia are not miners such as those at the uranium mines. They are the guides at the Jenolan Caves near Sydney. These guides work only short shifts because there are high levels of natural radon gas released from minerals washed down in the underground rivers. The heavy gas cannot escape because the caves cannot be ventilated, for fear of destroying the cave formations.

Q. Why does the Earth 'hum'?
A. The constant movement of the earth's crust causes a humming sound that can be detected by low frequency sound receiving devices.

Q. Are there mountains under the ocean?
A. There are mountains as high as Mt Everest under the ocean.

Q. What is the largest volcanic eruption observed by humans?
A. In 1815, an Indonesian mountain named Mount Tambora erupted with a force equivalent to 800 million tonnes explosive. This eruption was sixteen times more powerful than the largest nuclear bomb ever exploded.

Q. How is pumicestone made?
A. Pumicestone is an igneous volcanic rock formed when lava was thrown upwards into the air. Air bubbles were trapped inside the rock so it can float on water!

Q. How are tsunamis formed?
A. Tsunamis are tidal waves caused by underwater earthquakes.