Geological Strata: They’re Everywhere

Grand Canyon Rock Strata

Evidence for the global flood

by Jonathan O’Brien

Sedimentologist Guy Berthault was one of a team who made an important discovery regarding how the world’s sedimentary layers were deposited. These geological strata are clearly-defined beds of sedimentary rock that often have the appearance of bands or stripes of alternating or repeating layers. Most people have noticed them in cliffs, where they are often seen in side view. Grand Canyon comes to mind, where bold horizontal layering in the sides of the canyon is a major visual feature.

Geologists once thought that all such layers formed upwards. This conventional view of layer formation was one of the three principles of stratigraphy identified by creationist geological pioneer Nicolaus Steno (1638–1686). However, today the typical way this is explained is that sand, silt, and clay settled to the bottom of a placid lake or sea, and accumulated over eons of time. Eventually, a significant layer of sediment formed, which slowly hardened into rock. Then, a new layer of sediment started to deposit on top of the first, and so on.

The extent and form of layers

Seen nearly everywhere, on all the continents, sedimentary rock strata cover some 75% of the earth’s land surface. Strata are often horizontal but can also be tilted. The tilting may be due to tectonic movement or to the angle of original deposition, as strata can deposit at gradients exceeding 30o. Some strata have been deformed into curves due to subsequent tectonic movement while the sediments were still soft. Sedimentary layers come in many different thicknesses and types, from enormous formations hundreds of metres deep, down to tiny laminae less than 1 mm thick.

These layered rock formations continue under the ground, right under our feet. Individual layers frequently continue, unbroken, over huge areas of the continents. Another way to visualize them is as vast ‘blankets’ of rock, on top of each other in series. Some of these layers or blankets are flat, and others are heavily ‘rumpled’. Clean, knife-edge contact surfaces between layers are common.

Layers covering large areas of continents are extremely difficult or impossible to explain using standard uniformitarian explanations of sediment deposition, as we don’t see depositional layers of such vast geographical extent and magnitude forming today. So how did all this incredible layering come about?…

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image credit: Sonaal Bangera