[OAB 69] Dr. Gentry also found radiohalos in coalified wood in the Colorado Plateau (R.V. Gentry et al, Science, v.194, pp.315-318 (15 Oct 1976)). This time the halos are due to polonium-210, which is the same element (and thus has the same chemical properties) as the polonium-218 discussed above (see Parentless polonium halos), but a different isotope and thus has different nuclear properties. For example, polonium-210 has a half-life of 138 days, much longer than polonium-218's half-life of 3 minutes. Many of the halos found by Gentry are elliptical rather than spherical, which, according to Gentry, indicates that they were formed while the wood was still relatively soft, and then were "squashed" into an elliptical shape when the wood was compressed. In some cases, there is an elliptical and a spherical halo centered at the same point. Gentry claims that the second halo was formed by polonium-210 derived from the decay of lead-210, a process that takes 50 to 100 years. Since the second halo is not "squashed" but spherical, Gentry claims that the compression of the wood must have been completed before the second halo formed, implying that the compression and coalification of wood occurs in less than 50 years. Gentry also claims that, since coalified wood containing these halos occurs in strata of various geological ages, all geological ages are suspect. Need rebuttal from knowledgable source. This claim is not present in the Defender's Bible, indicating that it has been abandoned by ICR as weak.¹