Clean, knife-edge contact surfaces between layers are common. 4 Some of these layers or blankets are flat, and others are heavily ‘rumpled’. Another way to visualize them is as vast ‘blankets’ of rock, on top of each other in series.

Individual layers frequently continue, unbroken, over huge areas of the continents. These layered rock formations continue under the ground, right under our feet. 3 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. Some strata have been deformed into curves due to subsequent tectonic movement while the sediments were still soft. The tilting may be due to tectonic movement or to the angle of original deposition, as strata can deposit at gradients exceeding 30 o. Strata are often horizontal but can also be tilted. Seen nearly everywhere, on all the continents, sedimentary rock strata cover some 75% of the earth’s land surface. Then, a new layer of sediment started to deposit on top of the first, and so on. Eventually, a significant layer of sediment formed, which slowly hardened into rock. 2 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. This conventional view of layer formation was one of the three principles of stratigraphy identified by creationist geological pioneer Nicolaus Steno (1638–1686). Geologists once thought that all such layers formed upwards. Layers covering large areas of continents are extremely difficult or impossible to explain using standard uniformitarian explanations of sediment deposition. Grand Canyon comes to mind, where bold horizontal layering in the sides of the canyon is a major visual feature. Most people have noticed them in cliffs, where they are often seen in side view. 1 These geological strata are clearly-defined beds of sedimentary rock that often have the appearance of bands or stripes of alternating or repeating layers. Sedimentologist Guy Berthault was one of a team who made an important discovery regarding how the world’s sedimentary layers were deposited. The transitions between the five main mass extinctions can be seen in the rock strata.Geological strata: they’re everywhere Evidence for the global floodīy Jonathan O’Brien /profile_kojihirano Multiple horizontal layering in Grand Canyon.

Paleontologists have identified five strata in the fossil record that appear to show sudden and dramatic losses in biodiversity known as mass extinctions.Biodiversity Change through Geological Time.The deeper layers are older than the layers found at the top, which aids in determining the relative age of fossils found within the strata.

The layers of sedimentary rock, or strata, can be seen as horizontal bands of differently colored or differently structured materials exposed in this cliff.Strata are differentiated from each other by their different colors or compositions and are exposed in cliffs, quarries, and river banks.Stratigraphy is the science of understanding the strata, or layers, that form the sedimentary record.Carbon Dating and Estimating Fossil Age.The development of radiometric dating techniques in the early 20th century allowed geologists to determine the numerical or 'absolute' age of various strata and their included fossils.The totality of fossils, both discovered and undiscovered, and their placement in fossiliferous (fossil-containing) rock formations and sedimentary layers ( strata) is known as the fossil record.The observation that certain fossils were associated with certain rock strata led 19th century geologists to recognize a geological timescale.The Fossil Record as Evidence for Evolution.Examples of strata in the following topics:

Rock strata definition