Reading Rocks & Structures

You have seen many different types of rocks and geologic features in this course, with each having a story to tell of its origin and subsequent experiences. Whether it's a granite river rock, high-angle normal fault, or cross-bedded sandstone, they all represent the keys we can use to unlock the unknown. Understanding the language of geology allows us to learn the story of Earth's past (and future).

Figure 16-4. Checkin' out rocks in the field is what a geologist does!

At left, liesegang banding displayed in sandstones in the lower part of the Pennsylvanian Supai Group along the Tanner trail. These colored bands form from the rhythmic precipitation of minerals, typically iron oxides, in fluid-saturated rocks.
At right, a pegmatite dike in Hermit Creek (In the Grand Canyon) shows large crystals of alkali feldspar (red), plagioclase feldspar (white), quartz (gray), muscovite (silver), and amphibole/tourmaline (black).

Quiz Me! questions B22 through B35 involve rock identification and interpretation. If necessary, you can refer to the various rock identification charts from previous labs (Igneous Rock ID chart HERE / Sedimentary Rock ID Chart HERE / Metamorphic Rock ID chart HERE) / Sedimentary Structures ID chart HERE).