The fundamental process of oceanic subduction is explored in this chapter. It discusses subduction at global scale, including how subducted lithosphere sinks into the mantle, to the transition zone between the upper and lower mantle, and sometimes all the way to the core, creating subduction slab graveyards. These graveyards are linked to velocity variations near the mantle-core boundary. The subduction zone itself is explored at crustal levels from the slab to the top. This includes the bending, fracturing and serpentinization of the oceanic slab itself, the volcanic arc, the forearc basin. The chapter discusses hydration of the downgoing slab in the context of fluid circulation and melt formation, and how melting produces shallower magmatism. It also discusses the geochemical signature of arc magmatism and the associated back-arc heat flow. It also explores trench advance and trench retreat and consequences for subduction zone processes. Oblique subduction is covered together with strain partitioning into strike-slip and orthogonal motion along convergent plate boundaries. Examples from Central America, the Sunda trench (Sumatra), and from other location around the Pacific Ocean. Toward the end of the chapter, the complicated subject of subduction initiation is discussed.

Active collisional orogens represent the most impressive topographic features on Earth, with enormous masses of rocks being uplifted, exposed to surface erosion and sculptured into lofty mountains and deep valleys that show vast diversity in terms of climate, biodiversity, natural resources. In this chapter the modern Himalaya is presented in more detail, together with the Alpine system and the older Grenvillan orogenic belt that provides a deeper level of orogenic erosion. Differences are discussed and related to tectonic setting, duration of collisional phase, rigidness of colliding continents, synorogenic crustal heating and precollisional accretionary history. This chapter demonstrates that while the convergent Himalayan-Tibetan system generates a regime of thrust tectonics along its margins, the Tibetan plateau is dominated by extensional tectonics and strike-slip deformation. This is related to orogenic collapse and lateral extrusion linked to flow of partially molten middle to lower crust. Geophysical data are presented that give support to this interpretation. The Scandinavian Caledonides are presented as an example of a relatively short lived but major collisional orogen with deep continental subduction and a strong phase of extensional collapse.

The motion of plates is called plate kinematics. It can be relative or absolute, and both are explained in this chapter. Surface movements can be measured from space, and the results show that active deformation, volcanism and seismicity are focused along plate boundaries. This chapter emphasizes that the Earth‘s inner seismic structure confirms that the mantle is dynamic and in constant motion. Convective mantle flow has been suggested for a century and are a major field of research because of its indirect association with plate motions. Plumes represent more localized columns of upward moving hot mantle that generate crustal magmatism and volcanoes. They work together like a big internal machinery with implications for many geologic, geophysical and biologic processes. This chapter summarizes plate tectonics and the deeper plume and hotspot processes, and how it is possible to constrain and reconstruct plate motion into the past and, to some extent, also into the future.

This chapter describes how rifting may lead to continental break-up and the formation of a new ocean bound by passive continental margins. Passive continental margins define the transition from continental crust of normal thickness to oceanic crust. They are results of continental rifting that has caused the crust to break and give space to a new ocean. The break-up splits the rift into two, often unequal, parts that become tectonically inactive (passive) as the ocean starts to spread and widen. It is shown how some passive margins are magmatic with large amounts of volcanic activity, while other margins are magma-poor. Some margins are narrow, while others are wide and strongly thinned. The chapter also discusses hyperextended margins, where continental crust has been extended to the point that mantle rocks are exposed at sea bottom. This chapter presents these different settings and discusses how passive margin types are related to the final stages of rifting or initial stages of break-up. The type of magmatism involved is discussed, as are the depositional patterns that characterize the different kinds of passive margins. A number of natural examples are presented in this chapter, particularly from the south and north Atlantic margins.

Chapter 15 deals with the exciting first part of our planet, the time from which we have no actual rocks preserved. it summarizes our current understanding of how the planet first formed after formation of the solar system, how dust, stones, and gases collected into planetesimals that rapidly clustered to form planets. The importance of a molten planet Earth being hit by a Mars-size object is underscored, causing the formation of the Moon. In the following, Earth rapidly differentiated into a metallic core and a silicate mantle (magma ocean) that solidified from the bottom up in only a few million years. During solidification the magma ocean concentrated water into the shallow mantle, which set the stage for making the Earth’s oceans and generating a dynamic planet from its core to its surface. Emphasis is put on the information contained in Hadean zircon grains preserved in younger rocks, which has led some geologists to propose that the Hadean landscape resembled present-day Earth, with the presence of continents and oceans, and even the existence of some form of plate tectonics.

Chapter 2 provides a review of the fundamentals of Earth Science needed to understand the plate tectonic model. It provides an overview of the different kinds of forces involved in geoscience and continues on to stress, deformation and strain rate. The chapter explores the global stress pattern of the uppermost crust, shows how such information is retrieved, and discusses how it relates to the plate tectonic model. In this context, deformation structures such as faults, fabrics, folds and shear zones are briefly reviewed. Rheology, which relates to how the different parts of our planet react to stress, is also discussed. Further, simple models for rheological variations or profiles through the outer part of the planet are discussed, as such profiles strongly influence how lithospheric plates deform.

Chapter 13 deals with the ultimate stage of plate convergence, which is continent-continent collision. Collisional orogeny starts when an ocean is closed and two continental margins collides. Structures, processes and evolution of collisional mountain belts are covered from a general perspective, and different types of such orogens are outlined. Asymmetric versus symmetric belts are explained, and the overall structure of an orogenic belt, from the non-metamorphic foreland to the high-grade hinterland or core. The chapter explores foreland basins and foreland thrusting-related structures such as duplexes and detachment folds, and how deformed foreland layers can be restored to explore orogenic displacements involved. It explains why the hinterland heats up as crustal thickening continues or is maintained, and how this can enhance mid-crustal flow and orogenic plateau formation. Continental subduction is also discussed, where one of the continental margins is pulled down to sub-crustal depths and ultra-high pressures. Models for exhumation of (ultra)high-pressure rocks and the channel flow model are discussed, as is the role of syn- to postorogenic extension. The chapter also covers intracontinental orogeny, where no ocean is involved, and covers erosional aspects of continental orogens.

This chapter explains how pressure and density vary with depth and how they together control the different elevations of continental and oceanic regions, and reviews the fundamental concept of isostasy, the principle of flotation, where the lithospheric plates float on hot underlying mantle. It discusses Airy and Pratt models for isostasy and how and when high surface topography is compensated by a crustal root. The fundamental role of temperature is demonstrated in terms of the geotherm, heat production in the lithosphere, mantle and core, and how the Earth loses heat to the atmosphere through plate tectonic processes. The latter point also relates to how the geotherm varies through the upper crust, which again relates to geothermal energy exploitation. Temperature and pressure variations also control melting and magmatism, and this chapter covers the fundamental principles and characteristics of melting and magma crystallization. Also covered is metamorphic rocks and the metamorphic processes that occur in response to plate tectonic processes. Finally different kinds of sedimentary basins and their formation and classification according to plate tectonics are briefly reviewed.

This first of three chapters on orogeny presents a general introduction to mountain belts and further focuses on mountain belts formed by accretion of material onto a convergent plate boundary. The chapter starts out emphasizing some of the many tectonic scenarios that can lead to accretionary orogeny. The first example covered is Taiwan, where the transition from a regular accretionary wedge to an actual orogenic belt created by arc collision can be studied. Slab tear and the flipping of subduction is also covered by this example. The prime example of an accretionary mountain belt is the Andes, which is given special attention in this chapter with several maps and profiles. The Andes mountain chain shows lateral variations in terms of timing of orogenic initiation, orogenic events, arc collisions, magmatism, topographic development, strain and width. The chapter also covers the lateral and temporal variation in subduction zone dip and its implications. It continues by exploring tectonostratigraphic terranes and uses the North American Cordillera as the main example. The growth of western North America through repeated accretionary events is also explored, before exploring implications of accretionary orogeny for surface processes, climate and biodiversity.

This last chapter of the book focuses on the Archean and Proterozoic part of the Earth’s history, bridging the rapidly changing processes of early Earth with modern plate tectonics as dealt with in Chapters 1-14. It discusses the common Archean (4-2.5 billion years) granite and greenstone terranes and how they may reflect specific tectonic conditions associated with gravitational instabilities and tectonic accretion. Although different from today’s subduction-related accretion systems, these tectonic processes allowed for crustal accretion and amalgamation into (super)cratons. Proterozoic (2.5-0.54 billion years) terranes are widespread as accretionary complexes between or along Archean cratons. The chapter discusses how Paleomagnetic techniques and stratigraphic correlations constrain continental drift throughout the Proterozoic, and how their paths define cycles of supercontinent assembly, tenure, and dispersal. Evidence of modern plate tectonics are also discussed, and a lot of Proterozoic geology seems to be linked to plate tectonics, even though high-pressure rocks (eclogite, blueschist) are rare. It is concluded that the age and mechanism of onset of plate tectonics remains a controversial and fascinating topic that will continue to evolve into the future.

This chapter deals with the strike-slip fault zones that systematically offset midocean spreading ridges such as the mid-Atlantic ridge. Transform faults are one of three types of plate boundaries and are the active part connecting spreading ridge segments. The chapter investigates these in terms of size, distribution, dynamics, kinematics and seismicity. It looks at how transform faults relate and contrast to their mostly inactive extensions called fracture zones. Fracture zones can typically be traced across the ocean and record information about spreading direction and relative plate motions through geologic time. The chapter also discusses the origin of transform faults and how they provide a link to the mantle and their role as vertical conduits in terms of fluid flow between the mantle and the ocean floor. Several examples are shown where structural and seismic details are shown. This chapter also discusses complications caused by changes in opening direction, creating both transpressional and transtensional deformation along transform faults, and over time, curved fracture zones.

Chapter 6 covers continental rifting and rift-related processes that operate when continental lithosphere is thinned and broken. It covers the two fundamental modes of rift initiation; active and passive rifting. It also cover the role of mantle plumes and pre-rift structures that weaken the lithosphere. Magmatism typically varies along rift systems and is often related to plume influence during rift initiation. The main structural elements of rifts are presented, from rift transfer zones to fault relay ramps, together with the evolution of rifts in terms of fault growth, strain, crustal thinning and rift (a)symmetry. While some rifts open orthogonally, most rifts experience oblique rifting. Other rifts again show evidence of two or more phases of extension, and the interference between the two phases in terms of fault orientation and interaction is discussed. Different tectonic settings, such as back-arc rifting, transform fault settings, and orogen-related rifting are covered. The deposition of sediments in relation to structural elements is important, and both synrift and postrift sedimentation are discussed. Rifts also host important hydrocarbon and mineral resources, and examples from northern Europe and North America are provided in this chapter.

The Earth’s interior is the focus of this chapter, where we present the most important methods and data sources that allow us to gain information about the inside of our planet. Seismic waves give us refraction and reflection data and are used together with magnetic and gravity anomaly data in increasingly sophisticated ways. Seismic tomography is presented, which provides images and models of the interior. In this chapter it is shown how variations in S and P wave velocities are essential to our understanding of Earth’s interior, and how different kinds of geophysical data can be used to generate anomaly images that reflect rheologic variations, magma, partial melting and phase transformations. Some parts of the planet are dominated by descending cool lithosphere and mantle, while others are regions of net upwelling. The deep geodynamic processes are related to plate motions, but in a complex way that needs a better understanding.

In this first chapter, the concept of plate tectonics is briefly defined along with related terms such as tectonics, geotectonics, geodynamics and mantle dynamics. The uniqueness of Earth’s active plate tectonics is emphasized through comparisons with our neighboring planets, where asteroid impacts and volcanism tend to be important. Faults, folds and evidence of volcanism are common on many planets, but they are not related to plate tectonic processes. The Earth’s continents and oceans, zones of volcanism, seismic activity and topographic expression are not matched with any other planet in our solar system, and the chapter emphasizes that the plate tectonic model is able to explain first-order tectonic features and processes on Earth, and how it influences topography, climate and the evolution of life.

Chapter 8 gives an overview of the general structure and composition of oceanic lithosphere – the most common type of lithosphere on Earth. Its thickness, layered structure, seismicity, variation in seafloor elevation, magnetic anomaly pattern and composition are put in context of oceanic spreading and associated processes. The range of spreading rates, from ultraslow to superfast, is discussed. Differences in spreading rate have implications for the size of the magma chamber under the spreading ridge and therefore for the thicknesses of the different oceanic crustal layers. Slow spreading also favors exhumation of mantle and the formation of extensional detachments and core complexes. In this chapter the crystallization of melt to form oceanic crust is discussed along with the formation of hydrothermal mineralization and smokers. Hydrothermal activity produces ores that represent important metal resources that may be mined in the future. This chapter also presents ophiolites, oceanic crust on land, and simple models for obduction.