The 366 daily episodes in 2014 were chronological snapshots of earth history, beginning with the Precambrian in January and on to the Cenozoic in December. You can find them all in the index in the right sidebar. In 2015, the daily episodes for each month were assembled into monthly packages, and a few new episodes were posted. Now, the blog/podcast is on a weekly schedule with diverse topics, and the Facebook Page showcases photos on Mineral Monday and Fossil Friday. Thanks for your interest!

Monday, January 13, 2014

January 3: The Late Heavy Bombardment: 4.1 to 3.9 billion years ago

By Richard I. Gibson

The Late Heavy Bombardment was 200 million years of meteor collisions with the Earth and Moon. At least it probably happened, and it may have re-set the timing for age dates of earth rocks, a possible explanation for why the oldest rocks (which we’ll discuss tomorrow) are younger than this event that (probably) took place about 4.1 to 3.9 billion years ago.

Note that we’ve changed the sequence of this entry from the book, where it was on January 4. This makes the order of events more accurate.  Moon image from NASA (public domain). 

Listen to the podcast:


  1. I wanted to ask how the Late Heavy Bombardment hypothesis holds up to scientific scrutiny and the evidence supporting its existence

  2. When one listens to this podcast, one might wonder, "if there are no rocks older than 3.8 billion years old, then how do we know that the Earth is 4.6 billion years old. Good site below on how scientists came to the 4.6 billion years figure from the USGS: