Hi Andrew! I have listened to all the JRE podcasts with Randall Carlson and several of his other posts around the internet. He is certainly extremely knowledgeable and a great source. However, I do not believe that he is interpreting the mechanism that caused the change appropriately. It is a very complex subject, because there are many nuances of detail.
Firstly, he accepts radiometric dating as a valid metric. While the dating since ~12,000 years ago may be generally accurate'ish, I firmly believe that there is a very large assumption that the Earth has not undergone any drastic change that may cause dating prior to this "event" to be substantially miscalculated in absolute senses.
This is because of the second most important thing he does not include in his considerations, nor most models out there: the Earth expanded. This is not a question, but rather is only a matter of what exactly happened in the process. Plate tectonics is a complete misinterpretation that, when included in any explanation for the history of Earth, utterly misleads every other aspect of the model. The question of "how" is a matter of physics, which is a very detailed answer that all I can do is suggest you to look carefully through my other posts here and consider checking out my book (audio linked above).
This is extremely important when it comes to Carlson's work. As he interprets the Earth to be extremely old, billions of years as per radiometric dating analysis, he is open to there being a vast number of impacts as well as a high probability of impacts across its history. However, if one is not so certain of the radiometric dating process, then they will not hold it as an absolute but rather as something of note. This opens the door to the possibility that a catastrophic event, particularly one linked to what Randall Carlson discusses, produced a drastic change in the rate of radioactive decay and made it appear as if the Earth's age was much older when basing it off the present radioactive decay rates. It is an assumption that this is the case, however.
When the Earth is considered to possibility be younger than claimed by radiometric dating, then the question of the frequency of impacts comes into play. They do not occur frequently and with a much shorter span of time for them to occur within the probability becomes much lower. So much lower that all impact craters are questionable. I literally just finished writing a follow-up article on impact craters, The Not-So Impact Craters.
My personal interpretation, which is hard to explain the details of why it is the case in a short comment, is that the Earth was physically smaller and it had more energy (mass) into it than it was releasing. This led to a buildup that led to the sudden and rapid transformation of Earth when sufficient activation energy was input. The crust of the Earth then literally shattered along the edges of what we call the continental crust and then the Earth was free to expand outward to a new steady-state. As it did this, the oceanic floor was produced and water which was built up due to being literally created inside of the Earth (where an electromagnetic field merges, it is composed of particles that combine and fuse into larger particles such as hydrogen and oxygen) was released. This water then flooded across the planet, as well as Earth shattering earthquakes rippling through the crust. This produced mountains and all the features we see on the globe today, while moving continents into new positions where they then became stable as the oceanic floor was created and their positions became largely locked once more as the water then receded to the newly created ocean basins.
This is therefore not repetitive. Carlson interprets the impact as melting the glaciers and causing flooding, but in reality the massive flooding is even beyond his interpretations because he is not thinking globally enough. That is why I point to the Himalayas and Indonesia being literally created in this sudden event. In fact, all mountain ranges we see today are related. The Rockies, Appalachians, Andes, Himalayan; they were all caused by this event. It is no accident that the Rockies and Andes are along the Pacific Ocean, and the Ring of Fire surrounding it. This is where the Earth shattering epicenter occurred, sending out shockwaves creating deep trenches, volcanic arcs, and so on.
Carolina Bays also were caused due to water runoff after the Appalachian mountains were formed which is why the bays are all angled specifically in the direction from the Appalachian towards the ocean (Northwest to Southeast along the eastern coast of the US and North to South as they approach and cross Florida).
Physics is my "expertise", but unless we start from the Expanding Earth geology will remain completely off-base.
In my interpretation, Randall Carlson is extremely knowledgeable and I believe he would change his perspective if he gave these particulars, and the physics of the Expanding Earth, more rigorous consideration. I suspect most of these concepts have simply not occurred to him or crossed his path, so he considers a comet impact to be the most likely culprit of what he recognizes occurred: massive flooding and extinction and reverting the human race "back to the stone age".
I do love him, he's a great source. I am sure I am wrong in places, but understanding is a process that comes with time, focus, and consideration to as many possibilities as we are able to expose ourselves to.
RE: Earth History: The Himalayas as a Key to Understanding