The Rock Cycle Guided Reading and Study Answers
Figure 1. The different colors and textures seen in this rock are caused by the presence of dissimilar minerals.
Introduction
There are three types of rocks: igneous, sedimentary and metamorphic. Each of these types is part of the rock bike. Through changes in conditions i rock type tin get another rock type. Or it can become a dissimilar rock of the aforementioned type.
What Are Rocks?
A rock is a naturally formed, non-living earth textile. Rocks are made of collections of mineral grains that are held together in a firm, solid mass (figure i).
How is a rock different from a mineral? Rocks are made of minerals. The mineral grains in a rock may be so tiny that you can merely see them with a microscope, or they may be equally large as your fingernail or even your finger (figure 1).
Figure two. A pegmatite from South Dakota with crystals of lepidolite, tourmaline, and quartz (1 cm scale on the upper left).
Rocks are identified primarily past the minerals they comprise and by their texture. Each type of rock has a distinctive ready of minerals. A rock may be made of grains of all ane mineral blazon, such every bit quartzite. Much more commonly, rocks are made of a mixture of different minerals. Texture is a description of the size, shape, and arrangement of mineral grains. Are the two samples in effigy 2 the same stone type? Do they have the same minerals? The same texture?
Figure 3. Rock samples.
| Sample | Minerals | Texture | Formation | Rock type |
|---|---|---|---|---|
| Sample 1 | plagioclase, quartz, hornblende, pyroxene | Crystals, visible to naked center | Magma cooled slowly | Diorite |
| Sample 2 | plagioclase, hornblende, pyroxene | Crystals are tiny or microscopic | Magma erupted and cooled speedily | Andesite |
As seen in table 1, these two rocks accept the same chemical limerick and contain mostly the aforementioned minerals, only they exercise not have the same texture. Sample 1 has visible mineral grains, but Sample two has very tiny or invisible grains. The two unlike textures bespeak dissimilar histories. Sample 1 is a diorite, a rock that cooled slowly from magma (molten rock) cloak-and-dagger. Sample 2 is an andesite, a rock that cooled quickly from a very like magma that erupted onto World's surface.
Three Chief Categories of Rocks
Rocks are classified into three major groups according to how they form. Rocks can be studied in hand samples that tin be moved from their original location. Rocks can also be studied in outcrop, exposed rock formations that are attached to the footing, at the location where they are establish.
Igneous Rocks
Igneous rocks grade from cooling magma. Magma that erupts onto World's surface is lava, equally seen in figure four. The chemical composition of the magma and the rate at which it cools determine what stone forms as the minerals cool and crystallize.
Figure 4. This flowing lava is molten rock that will harden into an igneous stone.
Sedimentary Rocks
Sedimentary rocks form by the compaction and cementing together of sediments, cleaved pieces of rock-similar gravel, sand, silt, or dirt (figure five). Those sediments can be formed from the weathering and erosion of preexisting rocks. Sedimentary rocks also include chemical precipitates, the solid materials left behind later a liquid evaporates.
Figure v. This sedimentary rock is made of sand that is cemented together to form a sandstone.
Metamorphic Rocks
Metamorphic rocks grade when the minerals in an existing rock are changed by oestrus or pressure level within the Earth. Run into figure 6 for an example of a metamorphic rock.
Effigy vi. Quartzite is a metamorphic rock formed when quartz sandstone is exposed to heat and pressure level within the Earth.
A simple explanation of the three rock types and how to identify them tin can be seen in this video:
This video discusses how to place igneous rocks:
This video discusses how to identify a metamorphic rocks:
This Science Fabricated Fun video discusses the conditions nether which the three main rock types form:
The Rock Cycle
Effigy 7. James Hutton is considered the Father of Geology.
Rocks change every bit a issue of natural processes that are taking place all the time. Most changes happen very slowly; many have identify below the Earth's surface, so we may not even notice the changes. Although nosotros may not run into the changes, the physical and chemical properties of rocks are constantly irresolute in a natural, never-ending cycle chosen the rock bike.
The concept of the rock wheel was first developed by James Hutton, an eighteenth century scientist oftentimes called the "Father of Geology" (shown in figure vii). Hutton recognized that geologic processes have "no [sign] of a beginning, and no prospect of an end." The processes involved in the rock bike often take place over millions of years. And then on the calibration of a man lifetime, rocks announced to be "rock solid" and unchanging, but in the longer term, modify is always taking place.
In the stone cycle, illustrated in figure 8, the 3 main stone types—igneous, sedimentary, and metamorphic—are shown. Arrows connecting the iii stone types bear witness the processes that change ane rock type into another. The cycle has no beginning and no end. Rocks deep inside the Earth are right now becoming other types of rocks. Rocks at the surface are lying in place earlier they are next exposed to a process that will change them.
Figure 8. The Rock Cycle.
Processes of the Rock Wheel
Several processes tin turn one type of rock into another type of rock. The primal processes of the rock cycle are crystallization, erosion and sedimentation, and metamorphism.
Crystallization
Magma cools either underground or on the surface and hardens into an igneous rock. Every bit the magma cools, different crystals course at dissimilar temperatures, undergoing crystallization. For case, the mineral olivine crystallizes out of magma at much college temperatures than quartz. The charge per unit of cooling determines how much time the crystals volition have to form. Tiresome cooling produces larger crystals.
Erosion and Sedimentation
Weathering wears rocks at the Globe'southward surface down into smaller pieces. The small fragments are chosen sediments. Running water, ice, and gravity all transport these sediments from one place to another by erosion. During sedimentation, the sediments are laid down or deposited. In order to class a sedimentary rock, the accumulated sediment must become compacted and cemented together.
Metamorphism
When a rock is exposed to farthermost heat and pressure inside the Earth only does not melt, the rock becomes metamorphosed. Metamorphism may change the mineral limerick and the texture of the rock. For that reason, a metamorphic rock may have a new mineral composition and/or texture.
Lesson Summary
- Rocks are collections of minerals of diverse sizes and types.
- The three primary rock types are igneous, sedimentary, and metamorphic.
- Crystallization, erosion and sedimentation, and metamorphism transform ane rock type into some other or change sediments into rock.
- The rock cycle describes the transformations of one type of rock to another.
Reflection Questions
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The Rock Cycle Guided Reading and Study Answers
Source: https://courses.lumenlearning.com/geology/chapter/reading-the-rock-cycle/