CHAPTER 3 Earth Systems: Processes and Interactions Major Concepts and Questions Addressed in This Chapter A What is the rock cycle, and how is it related to plate F How do the atmosphere and continental configuration tectonics and the tectonic cycle? a ect ocean circulation? B What are the major types of rocks, and how do we infer G What accounts for the distribution and diversity of how and where they formed? plants and animals over Earth’s surface? C What are the major patterns of atmospheric H How is the availability of energy related to the structure circulation? of biologic communities? D How does atmospheric circulation a ect the I How are nutrients and other elements recycled, and distribution of heat and moisture over Earth’s surface? why is nutrient recycling important? E How fast do the oceans circulate? J How has the tectonic cycle a ected the atmosphere and hydrosphere? Chapter Outline 3.1 The Solid Earth System: Components and 3.3 Atmosphere and Its Circulation Processes BOX 3.1 Asian Monsoon: Influence of Large Land 3.2 Rock Cycle Masses on Atmospheric Circulation and the 3.2.1 Igneous rocks Hydrologic Cycle Intrusive igneous rocks: occurrence, texture, 3.4 The Hydrosphere and composition 3.4.1 Hydrologic cycle Extrusive igneous rocks: occurrence, texture, 3.4.2 Ocean circulation and composition 3.5 The Biosphere How do di erent kinds of magmas form? 3.5.1 Biogeography: distribution of plants and 3.2.2 Sedimentary rocks animals over Earth’s surface 3.2.3 Metamorphic rocks 3.5.2 Energy relationships Metamorphic rocks: texture and mineralogy 3.5.3 Biogeochemical cycles Types of metamorphism 3.6 The Tectonic Cycle and Earth Systems Yellowstone Gorge, Yellowstone National Park, Wyoming. The bright colors of the rocks result from lava ows and ash falls. © Filip Fuxa/Shutterstock, Inc. 56 © Jones & Bartlett Learning, LLC, an Ascend Learning Company. NOT FOR SALE OR DISTRIBUTION 9781284457162_CH03_056_084.indd 56 07/11/16 5:28 pm 3.1 The Solid Earth System: 3.2 Rock Cycle Components and Processes The major cycle operating within the solid Earth sys- B tem, especially the lithosphere, is the rock cycle Chapter 3 examines each of Earth’s major systems in (Figure 3.1 ). The rock cycle involves the formation and A greater detail. As we proceed, recall the basic features destruction of the three major rock types, or lithologies : igne- of natural systems introduced in Chapter 1: (1) each major ous , sedimentary , and metamorphic . Igneous rocks are Earth system consists of a series of parts or compartments those that have cooled and solidified from magma (from the that comprise a larger integrated and complex whole, Latin, for “characterized by fire”). (2) each system is an open system that exchanges matter and In an idealized example of the rock cycle, igneous energy with the environment, and (3) each system behaves rocks erode to produce sedimentary rocks that are later in a cyclic manner because of the flow of matter and energy metamorphosed and then melted to produce igneous rocks through the system. ( Figure 3.1 ). Usually, though, the rock cycle does not func- The flows of matter and energy within and between tion this simply. Depending on conditions, all preexisting systems are known as fluxes. This chapter emphasizes two rocks, whether they are igneous, sedimentary, or metamor- major features of the fluxes of matter and energy: phic, can be subjected to any one or more of the processes 1. Fluxes of matter and energy within systems and between of the rock cycle out of this sequence. Igneous rocks can, systems are cyclic. for example, be metamorphosed without first having been 2. Systems interact with one another through the uxes of eroded; metamorphic rocks can erode to produce sedimen- matter and energy. tary rocks; sedimentary rocks can be metamorphosed; or sedimentary rocks can become caught up in a “sedimentary Recall, for example, that plate tectonics is driven by loop” in which they are recycled through the processes of the flow of heat, which is itself produced by radioactive erosion, transport, deposition, and lithification all over again decay (Chapter 2). We will concentrate on how plate tec- to produce new sedimentary rocks. tonics interacts with each of the other major Earth systems beginning with the rock cycle, and then move on to the behavior of the modern atmosphere, the hydrosphere, and 3.2.1 Igneous rocks biosphere. This will allow us to then examine how the tec- tonic cycle has broadly influenced the other systems through Intrusive igneous rocks: occurrence, texture, geologic time. and composition Intrusive igneous rocks form beneath Earth’s surface. Bodies of solidified magma beneath Earth’s surface are referred to as plutons and vary substantially in size and shape. Gigantic plutons are called batholiths , whereas smaller dome-shaped Sediments Sedimentary rocks Lithification Sedimentary beds Erosion Erosion Metamorphism Transport Deposition Uplift Sedimentary beds Compression Igneous Metamorphic Lithospheric rocks Magma rocks plate Crystalization Melting Intrusion (a) (b) Data from: Hawkesworth, C. J., and A. I. A. Kemp. 2006. Nature , 443, 811–817. FIGURE 3.1 The rock cycle in relation to plate tectonics. The rock cycle involves the formation of molten magma and its intrusion into surrounding rocks or extrusion onto the Earth’s surface as volcanoes; upli , weathering and erosion, and redeposition to form sedimentary rocks; and metamorphism of preexisting rocks. Note the similarity of plate tectonics and the rock cycle. 3.2 Rock Cycle 57 © Jones & Bartlett Learning, LLC, an Ascend Learning Company. NOT FOR SALE OR DISTRIBUTION 9781284457162_CH03_056_084.indd 57 07/11/16 5:28 pm ones are called laccoliths (Figure 3.2). The dome shape of Although no one has ever seen an intrusive igneous laccoliths occurs because the magma is still relatively thick rock form, their emplacement beneath Earth’s surface can and tends to collect in one spot, resulting in an igneous be inferred from their coarse-grained, or phaneritic, texture body with a relatively flat base and domed upper surface. (“phaneritic” means visible, referring to the visible mineral Intrusive rocks can also occur as relatively thin bodies cut- faces in the rock). The term texture refers to the size, shape, ting across surrounding rocks (dikes) or injected parallel to and arrangement of the grains in a rock. Phaneritic textures strata (sills). One of the most spectacular sills is the Pali- occur when minerals in the rock exhibit relatively large, sades Sill, located along the Hudson River, north of New blocky mineral faces that make them easily visible. This hap- York City; the Palisades are composed primarily of igneous pens when the flux of heat from the magma to the surround- rocks emplaced as the supercontinent Pangaea rifted apart ing environment occurs very slowly, giving the crystal faces (Figure 3.3). sufficient time to grow into visible surfaces (Figure 3.4). Active Recent Cinder volcanism lava flows cone Laccolith Volcano Dike Sill Magma chamber Batholith (a) Reproduced from: U.S. Geological Survey (http://pubs.usgs.gov/of/2004/1007/volcanic.html). Accessed April 27, 2011. (b) Courtesy of Dr. Allan Thompson, University of Delaware. FIGURE 3.2 (a) Intrusive igneous rock bodies: batholiths, laccoliths, dikes, and sills. (b) Igneous dikes cut across one another in this outcrop. We can use cross-cutting relationships like this to date rocks (see Chapter 5). 58 Chapter 3 Earth Systems: Processes and Interactions © Jones & Bartlett Learning, LLC, an Ascend Learning Company. NOT FOR SALE OR DISTRIBUTION 9781284457162_CH03_056_084.indd 58 07/11/16 5:28 pm ultramafic rocks of the mantle give rise to mafic intrusive igne- ous rocks called gabbros (Figure 3.4). Gabbros are very dark in color because they contain relatively large amounts of iron and magnesium. Gabbros are probably common at the base of continental crust, and the boundary between ultramafic and gabbroic rocks is typically interpreted as the base of the oce- anic crust. Diabase is a more medium-grained mafic igneous rock that is often found in dikes and sills. Most continental crust is composed of granite, or rocks of “granitic” composition (Figure 3.4). The term “granitic” means the continental crust has an overall chemical com- position similar, but not necessarily identical, to granite. Granites consist predominantly of the minerals potassium feldspar and silica-rich minerals such as quartz, and paper- like micas; hence, granitic rocks are sometimes referred to Courtesy of Fred Wehner, www.tug44.org. as being felsic. Between gabbro and granite are igneous rocks of inter- FIGURE 3.3 The Palisades Sill along the Hudson River, north of mediate chemical composition. Like granite, these rocks also New York City. These rocks are enriched in the mineral olivine and tend to be associated with continental crust. One of the most were intruded during the early riing of the supercontinent Pangaea important of these rocks is diorite. Unlike granite, diorite (see the section “Tectonic Cycle” in Chapter 2). does not have visible quartz crystals (Figure 3.4). Its white and dark grains tend to impart a salt-and-pepper appearance Intrusive igneous rocks also vary according to their chem- to it. Although diorite is sometimes involved in mountain ical (mineralogic) composition. Rocks that are highly enriched building or other tectonic activity, granite is more commonly in magnesium and iron, such as those within the mantle, are intruded as large felsic bodies. So, too, are granodiorites, referred to as ultramafic. Rocks of the mantle are thought which are grayish rocks with a composition intermediate to consist mainly of peridotite. At shallower depths in the between diorite and granite (Figure 3.4). Granodiorites, in mantle, where lower pressures and temperatures are found, part, form the enormous batholiths of the Sierra Nevada of (a) © Tyler Boyes/Shutterstock, Inc.