![]() These might be gemstones in jewelry or rocks that someone collected. You or your family members probably have some rocks of your own. With the above terminology in hand, you are ready to investigate the three basic rock types and their formation in a little more detail. That is why the singular and plural forms are often used interchangeably. Note, however, that because individual rocks could in principle break off from the walls at any time, it doesn’t really matter whether we refer to the “rock” or “rocks” that make up the Grand Canyon walls. When we talk about the “rocks of the Grand Canyon,” we are talking about all the individual rocks that we could find there. When we talk about plural rocks, we are referring to sets of objects that are made of rock.Īs a simple example, when we refer to the “rock layers” of the Grand Canyon, we are talking about the fact that the layers are made of the material that we call rock.When we talk about singular rock, we are generally referring to rock as a type of material that is solid and made from minerals.Note that these three terms are often used in interchangeably, which makes sense because fossils are found within rocks, and both rocks and fossils are studied in geology.įinally, a less crucial but sometimes surprising bit of terminology concerns whether we should talk about singular “rock” or plural “rocks.” The answer is that we tend to use both forms interchangeably, but there’s a subtle distinction in how we generally use the terms: The geological record encompasses both the rock record and fossil record. ![]() The fossil record is very similar, but refers to the information that can be read from fossils of organisms that died in the distant past.For example, we say that the walls of the Grand Canyon contain a rock record that stretches through hundreds of millions of years of time. The rock record refers to the history of our planet that can be read from individual rocks or from layers of rocks.With this in mind, geologists refer to the story that they can read from rocks and fossils as either the rock record, the fossil record, or the geological record. The general term for anything that preserves evidence of a past event is the word record (as a noun), which comes from a Latin term meaning “remember.” For example, your school records show your past performance in school, your medical records describe your past medical visits and treatments, and a music record (or recording) provides a way to hear a piece of music that someone performed in the past. Our second piece of terminology concerns how we describe the story that geologists can read from rocks. Slide show 5.1.1–2 illustrates the definitions of and differences between rocks and minerals. Some rocks contain only a single mineral type, but most rocks are a mix of two or more different minerals that have become stuck together. Each different type of mineral has a distinct chemical composition, with its atoms arranged in an orderly way to give the mineral what we call its crystal structure.Let’s start with the terms “rock” and “mineral.” These terms are often used interchangeably, but in science, minerals are the building blocks of rocks. We will use the rock cycle to consider rock formation in more depth, but first we need to talk about a little more of the terminology of rocks. Figure 5.1.1-1 – This is Figure 4.38, repeated. The diagram of the rock cycle from Chapter 4 is repeated here. You already know the basics of the rock cycle (see Section 4.2.2), which describes how rocks can be changed between the three major types: igneous, sedimentary, and metamorphic. The first step in learning to read rocks is to understand their basic types and how they form. You’ll see that we frequently repeat the definitions (within the “…” bubbles) to try to help students remember the meanings. We recommend that you try to stick with the more “plain language” terms to the extent possible, but if you are preparing students for NGSS-based tests, then be sure they know the meanings of all of the terms. In addition, however, we’ve included some terms that we don’t really think are necessary for middle schoolers, but that are explicitly used in the NGSS. Part of the reason is simply that some of these terms are necessary to the discussion. You will notice that this section is much heavier on jargon than most of the rest of this book.
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