All right. I'll explain these concepts the best I can. My work in this field assignment was mostly to analyze and map structures and patterns in the sedimentary rocks found around Western Maryland. Sedimentary rocks are the most common type of rock exposed at the surface of the earth---they are formed by the gradual deposition and cementation of small particles of rock over long periods of time. Because of how they form, they are always originally deposited in horizontal layers stacked on top of one another. One unit of sedimentary rock is called a bed, and the study of how these beds overlay one another is called stratigraphy. Several beds together are collectively referred to as Strata, and the boundary between two beds is known as a stratigraphic boundary.Stratigraphic boundary
Now, although sedimentary rocks are always deposited in horizontal planes, it is very rare to find exposed sedimentary rocks in the field in nice flat layers. Usually, the geological forces behind Plate Tectonics exert themselves on the sedimentary layers and they become deformed. Sometimes this just means that the layers are tilted a bit but still retain their "flatness", if you will. That is what I am referring to when I say "bedding planes". Other times, the rocks and the layers that make them up are completely deformed, and are no longer in straight flat layers. This phenomenon is called Folding. There are several basic types of folds, but the two most common are called synclines and anticlines. Here's a simple picture that illustrates these folds:
These sedimentary layers were originally flat, but compressional forces squeezed them together so that they became crushed and folded against each other in that manner. If you look in the photos I provided, you'll see a lot of examples of folding in pictures 3-7. What I am referring to when I say "small-scale folding" or "centimeter-scale folding" is simply the relative size of the fold. Some folds can be tiny, and you can measure the distance from the limbs, or the two sides of the fold, in centimeters. On the other hand, some folds can be kilometers and kilometers across, such as the ones in the Appalachian Mountains near my home.
Tectonic foliations are a bit tougher for me to define. A tectonic foliation is a uniform planar deformation that comes about as the result of weak metamorphism in the original sedimentary rock. Under great heat and pressure, driven by tectonic forces in this case, sedimentary rocks will begin to rearrange themselves and recrystallize into new forms of rocks. This recrystallization will realign the orientation of the rocks so that you can identify uniform patterns in the rocks themselves roughly aligned to the same plane. I'm sorry if that's a bit technical and hard to understand, but if you look carefully at my last picture, you will see that the rock seems to have a wrinkled surface, and all these wrinkles are aligned in the same way in a plane that is rather close to horizontal. That is a tectonic foliation.
Geology is not just an Earth science, it is the earth science. It is the study of the Earth and its natural processes. It covers several fields: Vulcanology, the study of Volcanoes---my main interest---Petrology, the study of igneous and metamorphic rocks, Sedimentology, the study of sedimentary rocks, Mineralogy, the study of minerals, Seismology, the study of earthquakes, and Paleontology, the study of extinct life, are some of them. I was always interested in rocks and minerals, and chiefly volcanoes, and when I found out through a serendipitous college visit that you could study these things as your career, I knew immediately that that was what I wanted to do. I'm not exactly sure what you mean when you ask "are there different crystals and rock formations", but if you have any other specific questions, I'll be happy to answer them the best I can.Is geology an earth science? Are there different fields in geology? Are there different crystals and rock formations. I'm interested in learning more about this and your in the field so to speak. How did you get into wanting to become a geologist? Are there different types of crystals and rock formations and how do they form?
I know asking too much. Thanks for the great photos.