Rock such as basalt and thorium is radioactive.

岩钍这样的岩石具有放射性。

The heat is a leftover from  Earth's formation and from from the decay of radioactive elements like thorium and uranium  that shower the crust with a constant wave of radioactivity.

热量是地球形成时遗留下来的，以及钍等放射性元衰变产的，这些放射性元不断向地壳释放出持续的放射性波。

The ages of these flowstones can be determined by the ratio within them of the radioactive elements uranium and thorium.

这些流石的年龄可以通过其中放射性元钍的比例来确定。

In 2011, just before an earthquake struck the east coast of Japan, nearby researchers recorded surprisingly high concentrations of the radioactive isotope pair: radon and thoron.

2011年，就在地震袭击日本东海岸之际，附近的研究人员侦测到了高浓度的放射性同位组：氡钍，对此他们十分震惊。