Fig. 1.24. The most frequent fold types: A. symmetric fold; B. oblique fold; C. isoclinal fold, D. overturned fold; E. horizontal fold (after Báldi 1991)

Because of friction and the rigidity of the rock, the rocks cannot glide or flow past each other. Rather, stress builds up in rocks and when it reaches a level that exceeds the strain threshold, the accumulated potential energy is dissipated by the release of strain. In this case stress causes fractures by exceeding the rock strength, causing the rock to lose cohesion along its weakest plane. A fracture will sometimes form a deep fissure or crevice in the rock. This deformation creates propagation of fractures. Faults are active form of fracture in a geologic environment. Geologists can categorize faults into three groups based on the sense of slip: a fault where the relative movement (or slip) on the fault plane is approximately vertical is known as a normal fault, or reverse fault depending on direction of movement; where the slip is approximately horizontal, the fault is known as a transcurrent or strike-slip fault (Völgyesi 2002, Hartai 2003) (Fig. 1.25.).

1.6. Presentation

For more information on this chapter see the presentation below

Presentation

1.7. Self-checking tests

1 Introduce the formation and the inner structure of the Earth! 2 Characterize the rocks of the lithosphere! 3 Explain the locomotion types of the lithosphere plates!

2. 2. Fundamentals of geology II. (palaeoecological reconstruction)

2.1. 2.1. Stratigraphy

Nicholas Steno established the theoretical basis for stratigraphy when he reintroduced the law of superposition and introduced the principle of original horizontality and the principle of lateral continuity in a 1669 work on the fossilization of organic remains in layers of sediment. Steno, in his Dissertationis prodromus of 1669 is credited with three of the defining principles of the science of stratigraphy: the law of superposition: "...at the time when any given stratum was being formed, all the matter resting upon it was fluid, and, therefore, at the time when the lower stratum was being formed, none of the upper strata existed"; the principle of original horizontality: "Strata either perpendicular to the horizon or inclined to the horizon were at one time parallel to the horizon"; the principle of lateral continuity: "Material forming any stratum were continuous over the surface of the Earth unless some other solid bodies stood in the way"; and the principle of cross-cutting relationships: "If a body or discontinuity cuts across a stratum, it must have formed after that stratum." These principles were applied and extended in 1772 by Jean-Baptiste L. Romé de l'Isle. Steno's ideas still form the basis of stratigraphy and were key in the development of James Hutton's theory of infinitely repeating cycles of seabed deposition, uplifting, erosion, and submersion.

Using Steno’s theory we are able to determine the relative age of strata (Fig. 2.1.). There are several methods for stratigraphic correlation. The most common used are lithostratigraphy, biostratigraphy and chronostratigraphy.