Grand Canyon Unconformities and Deep Time – Part 2

Are there “incontrovertible” reasons to affirm a young Earth? What does it mean to be incontrovertible?  Some YEC seem to believe that this means that it is claimed by any YEC author that they appreciate.  It is easy to list claims that might sound impressive.  What happens if we dig into those claims?  Can they stand up to analysis?

Geologists interpret the tremendous amount of sedimentary rocks on the Earth to have been deposited over billions of years.  That is a big disconnect with YEC claims that the Earth is 6,000 years old.  Such sediment accumulations are often miles thick.  If this had been deposited over a 1-year period of time, that would indicate that the beds were almost contemporaneous, deposited at incredible rates by catastrophic processes. Is that what the rocks tell us?  Some YEC have made physical models that they interpret to be saying that much of the Earth’s sedimentary rock formed almost simultaneously.  This is another one the “incontrovertible” evidences from Paul Humber’s “Reasons to Affirm a Young Earth”.  (Humber 2013)

The reason given in this case is: 

• 18. “Two very distinct, Grand Canyon unconformities” Part 2

As with Part 1, first we will state distinctly the observation from nature and then the assertions derived from it.

2. The Great Unconformity

Most everyone agrees that a lot of sediment has been removed along the Great Unconformity. The name alone tells you it is very significant. (Figure 1).  Both Dr. Tim Clarey (ICR) (Clarey 2020) and Dr. Andrew Snelling (AIG) (Snelling 2021) interpret this surface to represent the base of deposits from Noah’s flood.  I have written more technical articles on the units involved here:  “Does Flood Geology explain the rocks in the Grand Canyon?”

Figure 1. Great Unconformity in the Grand Canyon.

In view of the assertions that are given here to support a young Earth, some key observations are relevant.

1. The Base of the Cambrian overlies rocks of many ages.

2. The Great Unconformity is recognized to be a composite surface that is comprised of several unconformities. (Figure 2) (Karlstrom 2019).

3. In some areas, the rocks under the unconformity were chemically weathered for a long period of time before being buried by later sediments such as the Tapeats Sandstone. (Sharp 1940)

4. The rocks beneath the unconformity were well lithified before at least the later erosive episodes as evidenced by the cobbles from the underlying rocks in the Tapeats and other overlying sediments.

Figure 2  Schematic cross-section through the Grand Canyon showing the Great Unconformity as a highly angular unconformity.

Discussion.

 The proposal that the Great Unconformity could not have resulted from erosion over 1 billion years has an element of truth in it.  No scientist believes that this unconformity developed by simple constant erosion for a billion years.  Even so, how slowly can the processes of geologic weathering and erosion take?  While they can be fairly rapid, think about the pyramids or other ancient stone monuments that have stood for millennia.  How long would it take to erode them away completely? 

• The gap in age is variable and the 1 billion years gap does not mean that there was 1 billion years of erosion. Imagine that some sand is laid down along the Colorado River today. (Figure 2)  If the Vishnu Schist happens to be  ~1.7 billion years old at the river, then the age gap between the sand and the schist is 1.7 billion years, but it does not at all mean that the Colorado River carved down for 1.7 billion years.  Many geological events intervened. Same with the Great Unconformity. (Point 1 above) 

• Geologists find that the Great Unconformity in the Grand Canyon is a complex surface that was formed by several long erosional periods of time. (Point 2 above) We are limited in what we can prove in terms of deposition or erosion during the time between the base of the Cambrian Tapeats and underlying rocks. As shown in the second figure, we can see that there was faulting and different levels of erosion, but how much was eroded is more difficult to be sure of. In some cases, we can correlate to areas where the unconformities are smaller or missing, but in this area, it is just an argument from silence. 

• While we don’t know how long it took to erode off the sediments, these were not loose sand and mud. (Point 4 above). They would have been harder to erode.

• In some areas, erosion at the base of the Tapeats cut down through the underlying rocks such as the Shinumo Quartzite and the Hakatai Shale and sets on what was at the time freshly eroded rock. The deposition might have been very soon after the erosion. As was mentioned in the earlier posts on unconformities, areas where the underlying rocks were chemically weathered indicate that rocks in other areas were exposed for a long time before being buried. (Point 3 above).  A lot of just non-deposition may have been involved, though we don’t know how deeply weathered the original rocks were, so we still don’t know exactly how much rock was removed by erosion.

Do the two unconformities given in the publication demand a young Earth?  Quite the opposite can be argued.  They support erosion and deposition over deep time. They reflect a rich and varied history on this planet. Earth might have been like other planets, dead and lifeless.  The unconformities reflect an active planet that has supported life amazingly for over 3.5 billion years.

Additional Information source:  “Missing Time: Gaps In the Rock Record” chapter from the book:  The Grand Canyon: Monument to Ancient Earth.

References Cited:

Clarey, Dr Timothy. 2020. Carved in Stone: Geologic Evidence of the Worldwide Flood. ICR Institute for Creation Research.

Hill, Carol. 2016. “The Grand Canyon, Monument to an Ancient Earth: Can Noah’s Flood Explain the Grand Canyon?” Perspectives on Science and Christian Faith 68 (4): 268–71.

Humber, Paul G. 2013. Reasons to Affirm a Young Earth. Vol. e-book revision. https://static1.squarespace.com/static/54235fb7e4b0dab08d8d81dd/t/57d6e6b3d482e999611d7888/1473701556828/ReasonsAffirmYE+CRS+e-book.pdf?fbclid=IwZXh0bgNhZW0CMTAAAR0J_JCi_6zH1KuNlHYrgIJjTAhCgOm4zwio8ks44k5CGnJIAiETnqThXLI_aem_BA94GfB1gm5q86tQj_pW2w.

Karlstrom, Karl E. 2019. “Parsing Grand Canyon’s Great Unconformity– Composite Erosion Surface From at Least Three Episodes Between 1,350 and 508 MA.” In . GSA. https://gsa.confex.com/gsa/2019AM/webprogram/Paper332195.html.

Sharp, Robert P. 1940. “Ep-Archean and Ep-Algonkian Erosion Surfaces, Grand Canyon, Arizona.” GSA Bulletin 51 (8): 1235–69. https://doi.org/10.1130/GSAB-51-1235.

Snelling, Andrew A. 2021. “The Petrology of the Tapeats Sandstone, Tonto Group, Grand Canyon, Arizona.” Answers Research Journal 14. https://assets.answersingenesis.org/doc/articles/pdf-versions/arj/v14/petrology_tapeats_sandstone.pdf.