Читать книгу Geology For Dummies - Alecia M. Spooner - Страница 40

Geologists describe characteristics of rocks with the intention of understanding the processes that formed those characteristics. For this reason, an observed characteristic, such as “layers,” will have different terms indicating what kind of process resulted in those layers. Here’s an example of what I mean:

 A rock with layers may be described as laminated. Laminations are thin layers formed by the accumulation of tiny particles that settle through standing water (such as at the bottom of a lake or pond). This layered (laminated) rock is a sedimentary rock.

 A rock with layers may also be described as foliated. Foliations are thin layers or sheets of minerals that are created by intense amounts of pressure and heat deep within the earth’s crust. This layered (foliated) rock is a metamorphic rock.

The layered characteristic of these rocks may seem similar at first glance but is actually the result of very different processes that occur under very different conditions on the earth. Closer inspection of the rocks (perhaps with a microscope) will reveal that the layers made of particles are different in appearance than the layers made of mineral sheets.