Does the high uranium content of granite contribute to its breakdown?

Answer 1

Granite with a high uranium content breaks down faster than does granite with less uranium in it, but it would be wise to think a bit more about this before we walk away. Let's look more closely to see what's going on.

Uranium (whichever isotope or isotopes we consider) is radioactive. Every atom is unstable, and has some probability of decay (by a method or methods specific to that isotope). Radioactive decay releases energy, either particulate or electromagnetic, or both, and these can easily break down the matrix of granite. Further, daughter products of uranium decay are often radioactive themselves, and their decay will release further energy causing more damage. There is a catch or two, however.

First, it should be noted that structural damage to granite owing to the decay of uranium within it happens on an atomicscale. In a larger sense, the damage to a granite sample is slight. Lastly, the half-life of uranium isotopes is generally very, very long; they decay slowly. It is certainly possible to take granite samples to the laboratory and find structural defects in the rock's matrix that were caused by radiation damage. And granite with a higher uranium content will reveal more damage than a sample that has less uranium in it. But it takes lifetimes for "significant" damage to a rock sample to occur owing to the decay of uranium (or its daughter products) within that granite. You won't see a granite plinth or monolith falling apart from radiation damage right in front of your eyes as you view it.

Answer 2

Yes, the high uranium content in granite can contribute to its breakdown due to the radioactive decay of uranium, which produces heat and causes the surrounding minerals in the granite to expand and contract. This process, known as radioactive decay weathering, can weaken the granite and lead to its physical breakdown over time.