Reasons to Believe

Grand Canyon Formed over Millions of Years


So exclaimed my then five-year-old son as our car approached the south rim of the Grand Canyon. His reaction echoes the sentiments of most people witnessing the grandeur of this natural wonder for the first time. The canyon ranges anywhere from four to eighteen miles wide, and it extends over 250 miles in length. Visible from the top rim, the turbulent rapids in the Colorado River nearly one mile below grind away at the rock in the canyon’s bottom. An impressive site indeed!

Most young-earth creationists (YECs) argue that a global flood during the time of Noah (which they typically date around 5,000 years ago) was responsible for laying down the bulk of the sediments which comprise the walls of the Grand Canyon as well as carving out the canyon itself. In contrast, the vast majority of the scientific community supports a model explaining that the Grand Canyon formed over millions of years as the Colorado River cut through the southwestern section of the Colorado Plateau. Furthermore, according to this model, the strata in the walls of the canyon were deposited throughout the last two billion years.

Most old-earth creationists (OECs) acknowledge the validity of the model developed by the scientific community and find it consistent with, and supportive of, the biblical text. Recently published data provides strong evidence for the model favored by the scientific community (hereafter referred to as the “prevailing scientific” model).

As the Colorado River cut through the Colorado Plateau, tectonic forces also pushed the plateau to higher elevations. Consequently, the level of the water table should have moved downward through the sedimentary layers that comprise the Grand Canyon walls today. Numerous caves existing in the canyon walls contain formations—called speleothems—that formed as water moves through the ground into the caves. One particular formation called a mammillary forms just below the groundwater table level.  

Three geologists from the University of New Mexico analyzed samples of these mammillaries from nine different sites to see how quickly the water table dropped during the formation of the Grand Canyon.1 The mammillaries only formed in any given cave when the groundwater level coincided with the cave’s location. After the groundwater level dropped below the cave, no new material was added to the mammillary formation. Thus, the team used radioisotope dating of the mammillary material to determine an absolute date when the water level matched the level of the cave. They used two different dating techniques to ensure that the measured dates were correct.

The data show that the older mammillary formations reside at the higher elevations above the current river level. Additionally, it took 17 million years for the groundwater table level to drop to its present location starting from an elevation 3,800 feet higher. The data also demonstrate that the western section of the Grand Canyon formed earlier than the eastern section and that the western section formed more slowly. All these results confirm the prevailing scientific model of how the Grand Canyon formed. In contrast, they present significant problems for the standard YEC model, which suggests that the groundwater level in the Grand Canyon dropped from the top of the Colorado Plateau to near its current level within a few years as the global flood subsided.

The most common response I hear from the YE community is that the dates obtained by radiometric dating are unreliable. However, the scientists performing the research used two different methods to verify the validity of the measured dates. Additionally, even if the dates are incorrect as the YE model posits, the YE model must still explain the coherent picture revealed by the data. For example, why are the oldest cave formations consistently higher above the river than more recently formed speleothems?  

While the data favors the prevailing scientific model currently, hundreds of additional caves exist in the Grand Canyon which should contain preserved mammillary formations. Thus, future tests will determine which model is correct. If the prevailing scientific model holds true, tests from these additional caves will continue to affirm that the Colorado River cut through the preexisting strata of the Colorado Plateau starting around 17 million years ago. On the other hand, if the YEC model is accurate, future research will explain the data discussed in this article (in the context of a few-thousand-years-old Earth) and show that the sedimentary layers and cave formations formed at the same time roughly 5,000 years ago.

I, along with the scholars at Reasons to Believe, expect future research to validate the prevailing scientific model, which supports a belief in old-earth creationism. Let the testing of this spectacular natural treasure begin.

Subjects: Scientific Evidence for an Old Earth

Dr. Jeff Zweerink

While many Christians and non-Christians see faith and science as in perpetual conflict, I find they integrate well. They operate by the same principles and are committed to discovering foundational truths. Read more about Dr. Jeff Zweerink.


  1. Victor Polyak, Carol Hill, and Yemane Asmerom, “Age and Evolution of the Grand Canyon Revealed by U-Pb Dating of Water Table-Type Speleothems,” Science 319 (March 7, 2008): 1377-80.