Earth’s Perfect Erosion Processes

It may not occur to many of us, but continental erosion from the ongoing collision between the Indian subcontinent and Asia has contributed to weathering processes that make advanced life on Earth possible. In my book Weathering Climate Change I explain why—for global human civilization to be possible—we must be living in the midst of an ice age cycle.¹ The cycle has been in place for about 2.58 million years, a tiny fraction of Earth’s life history. However, the Sun is brighter than it ever has been during the entire past 3.8-billion-year-long history of life. Thus, an ice age cycle seems unlikely.

During the human era, the Sun has been shining about 23% brighter than it did at the time of life’s origin. Aside from the current cycle, for about 90% of the past 3.8 billion years Earth has measured to be ice-free.

Onset of Rapid Silicate Weathering
Why is there an ice age cycle during the Sun’s brightest epoch? The answer to this conundrum can be found in the late Cenozoic cooling of Earth caused by a sharp decline in atmospheric carbon dioxide. (The Cenozoic era extends from 66 million years ago until the present.) Since carbon dioxide is a powerful greenhouse gas, its decline would mean that the atmosphere would trap much less of the Sun’s incoming radiation. Geologists have recognized that the decline arose from accelerated silicate weathering, driven especially by enhanced erosion that followed the tectonic collision between the Indian subcontinent and Asia. This collision formed the Himalayan Mountains and uplifted the Tibetan Plateau. The resulting high glaciers and steep slopes accelerated Earth’s continental erosion rate.

Silicate weathering takes place when rain falling on exposed silicates (continents are primarily composed of silicates) acts as a catalyst to convert silicates and atmospheric carbon dioxide into carbonates and sand. The chemical reaction is displayed below:

CaSiO₃ + 2CO₂ + H₂O → Ca⁺⁺ + 2HCO₃ + SiO₂
Ca⁺⁺ + 2HCO₃ → CaCO₃ + CO₂ + H₂O

The net reaction is:

CaSiO₃ + CO₂ → CaCO₃ + SiO₂

The example here is for calcium silicate. The reaction is the same for any other metal silicate.

Measurements Affirming Accelerated Silicate Weathering
One way scientists learn about Earth’s past climate is to study proxies. These are preserved physical characteristics of the past that stand in for direct meteorological measurements. Multiple chemical proxies confirm that accelerated silicate weathering occurred during the late Cenozoic. These proxies include strontium, osmium, and lithium isotope measurements.² Confirmation also comes from measurements of carbonate compensation depth.³ Furthermore, sedimentary records show a nearly fourfold worldwide acceleration of erosion rates during the late Cenozoic,⁴ and bedrock thermochronometric measurements in the world’s most mountainous regions reveal a twofold increase in erosion rates during the past 8 million years.⁵ The one proxy that has not fit this scenario is beryllium isotope measurements.

Three geochemists, Shilei Li, Steven Goldstein, and Maureen Raymo, did a deeper, more extensive study of beryllium isotope measurements.⁶ They produced a detailed beryllium cycle model that completely resolved the discrepancy between the beryllium records and all the other silicate weathering proxies. They showed how Be-10/Be-9 records permit up to an elevenfold increase in beryllium weathering during the late Cenozoic. Now, all the weathering and erosion proxies are consistent with current understanding of accelerated silicate weathering and terrestrial erosion during the late Cenozoic.

Initiation of an Ice Age Cycle without Runaway Cooling
The collision between the Indian subcontinent and Asia is ongoing. Consequently, the Himalayas and the Tibetan Plateau are still being pushed up. To prevent a runaway cooling where thick ice covers nearly all of Earth’s surface, there must be compensating factors that counterbalance the cooling from accelerated silicate weathering by just-right amounts.

In their paper, the three geochemists identified four compensating factors:

1. Degassed carbon dioxide from volcanism and metamorphism
2. Enhanced carbonate dissolution by sulfuric acid produced by pyrite weathering
3. Accelerated oxidation of organic carbon
4. Reduced basalt weathering

All four occurred at just-right rates as the global climate cooled.

Geologic Design Features
Combining the team’s research findings with a much broader study of geologic, atmospheric, hydrospheric, and biological histories that I have described in three books⁷ establishes an astounding fine-tuning of Earth and its life. Earth’s history reveals the opening of a brief time window—less than 12,000 years wide—for global human civilization to thrive. This discovery provides one more out of many examples in the geosciences that the more we learn about our planet and its history, the more evidence we uncover for the supernatural, super-intelligent handiwork of the Creator God of the Bible.

Endnotes

1. Hugh Ross, Weathering Climate Change (Covina, CA: RTB Press, 2020), 81–93.
2. Frank M. Richter, David B. Rowley, and Donald J. De Paolo, “Sr Isotope Evolution of Seawater: The Role of Tectonics,” Earth and Planetary Science Letters 109, nos. 1–2 (March 1992): 11–23, doi:10.1016/0012-821X(92)90070-C; Sambuddha Misra and Phillip N. Froelich, “Lithium Isotope History of Cenozoic Seawater: Changes in Silicate Weathering and Reverse Weathering,” Science 335, no. 6070 (February 17, 2012): 818–823, doi:10.1126/science.1214697.
3. Heiko Pälike et al., “A Cenozoic Record of the Equatorial Pacific Carbonate Compensation Depth,” Nature 488 (August 30, 2012): 609–614, doi:10.1038/nature11360; Siobhan M. Campbell et al., “Effects of Dynamic Topography on the Cenozoic Carbonate Compensation Depth,” Geochemistry, Geophysics, Geosystems 19, no. 4 (April 2018): 1025–1034, doi:10.1002/2017GC007386.
4. William W. Hay, James L. Sloan II, and Christopher N. Wold, “Mass/Age Distribution and Composition of Sediments on the Ocean Floor and the Global Rate of Sediment Subduction,” Journal of Geophysical Research: Solid Earth 93, no. B12 (December 10, 1988): 14933–14940, doi:10.1029/JB093iB12p14933; Peter Molnar, “Late Cenozoic Increase in Accumulation Rates of Terrestrial Sediment: How Might Climate Change Have Affected Erosion Rates?,” Annual Review of Earth and Planetary Sciences 32 (May 19, 2004): 67–89, doi:10.1146/annurev.earth.32.091003.143456.
5. Frédéric Herman et al., “Worldwide Acceleration of Mountain Erosion under a Cooling Climate,” Nature 504 (December 19, 2013): 423–426, doi:10.1038/nature12877.
6. Shilei Li, Steven L. Goldstein, and Maureen E. Raymo, “Neogene Continental Denudation and the Beryllium Conundrum,” Proceedings of the National Academy of Sciences USA 118, no. 42 (October 19, 2021): id. e2026456118, doi:10.1073/pnas.2026456118.
7. Hugh Ross, Improbable Planet (Grand Rapids, MI: Baker Books, 2016); Hugh Ross, Weathering Climate Change (Covina, CA: RTB Press, 2020); Hugh Ross, Designed to the Core (Covina, CA: RTB Press, 2022).