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Geosphere

The geosphere refers to the solid, inorganic portion of Earth, encompassing all rocks, minerals, sediments, soils, and landforms from the surface to the planet's interior, including the crust, mantle, and core.^[1] It constitutes the rocky foundation of the planet, shaped by geological processes and comprising approximately 94% oxygen, iron, silicon, and magnesium by volume in its solid components.^[1] Structurally, the geosphere is divided into chemical layers based on composition: the thin outer crust (divided into continental and oceanic types, 5–80 km thick), the extensive mantle (extending to about 2,900 km depth, primarily composed of peridotite), and the dense core (inner solid and outer liquid portions, mainly iron and nickel, from 2,900 km to Earth's center).^[2] Physically, it includes the rigid lithosphere (crust plus uppermost mantle, 0–280 km thick, broken into tectonic plates), the ductile asthenosphere beneath (driving plate motion through convection), and deeper rigid zones like the mesosphere.^[2] These layers interact dynamically, with processes such as plate tectonics causing continental drift, mountain building, earthquakes, and volcanism that continually reshape the surface.^[1] The geosphere interacts extensively with other Earth systems, influencing and being influenced by the atmosphere, hydrosphere, biosphere, and cryosphere.^[3] For instance, weathering and erosion by water and wind break down rocks into sediments, while tectonic activity exposes new minerals and affects climate through volcanic emissions.^[3] Biological processes, such as root growth and burrowing, further alter soils, and glacial ice from the cryosphere carves landscapes over time.^[3] These interconnections highlight the geosphere's role in sustaining Earth's habitability and driving long-term environmental changes.^[4]

Definition and Scope

Definition

The geosphere encompasses all rocky and metallic materials forming Earth's interior, extending from the crust to the core and excluding the hydrosphere and atmosphere.^[4]^[1] It represents the inorganic portion of the planet, including rocks, minerals, and landforms from surface features like mountains and ocean floors to deep-seated molten rock and heavy metals.^[5] The term "geosphere" derives from the Greek words "geo," meaning earth, and "sphaira," meaning sphere, and was first used in the 19th century to describe the solid layers of Earth.^[6]^[7] In Earth system science, the geosphere is one of four primary interacting spheres—alongside the atmosphere, hydrosphere, and biosphere—focusing on lithic materials and their geological cycles, such as the rock cycle.^[8]^[9] Key characteristics of the geosphere include its composition, which is dominated by silicate minerals in the crust and mantle, alongside metallic elements like iron and nickel in the core.^[10] These materials are subject to extreme internal pressures and temperatures, driving processes like convection and differentiation.^[5] The geosphere accounts for approximately 99% of Earth's total mass, underscoring its dominance in the planet's overall structure.^[11] The rigid outer layer of the geosphere is known as the lithosphere.^[4] The geosphere encompasses the entire solid Earth, including the crust, mantle, and core, whereas the lithosphere refers specifically to the uppermost rigid layer comprising the crust and the brittle upper portion of the mantle.^[1]^[12] This distinction highlights the geosphere's broader scope, which includes deeper, more ductile layers beneath the lithosphere that influence long-term planetary dynamics.^[4] In contrast, the pedosphere represents the thin soil layer at Earth's surface, formed through the interaction of weathering processes involving the lithosphere, atmosphere, hydrosphere, and biosphere, and serves as a dynamic interface rather than the full solid interior of the geosphere.^[13] As a subset of the geosphere, the pedosphere focuses on pedogenic materials like regolith and humus, excluding the vast subsurface rock volumes that define the geosphere's structural integrity.^[14] The anthroposphere, meanwhile, denotes the human-altered components within Earth's systems, such as urban infrastructures and agricultural modifications overlaid on the natural geosphere, emphasizing anthropogenic impacts over the unmodified solid Earth.^[15] This term underscores human agency in reshaping surface features, distinguishing it from the geosphere's natural lithic foundation.^[16] Within Earth system science, the geosphere functions as one of the primary spheres alongside the hydrosphere, atmosphere, and biosphere, but its definition remains centered on solid materials for Earth, excluding liquid water elements.^[3]

Historical Development

Ancient and Pre-Modern Concepts

In ancient Greek philosophy, particularly in the 4th century BCE, Aristotle conceptualized the Earth as the stationary center of the universe within a geocentric model composed of four elemental spheres. The innermost sphere, associated with the geosphere, represented the natural place for the heavy elements of earth and water, which naturally gravitated toward the center due to their density, forming a solid, spherical body beneath the lighter elements of air and fire.^[17] During the medieval and Renaissance periods, these ideas evolved under the influence of Ptolemaic astronomy, which reinforced the view of Earth as a static, layered sphere at the cosmic center, with its interior structured hierarchically by divine order. Minerals and metals within the geosphere were thought to form through alchemical processes involving the combination of sulfur and mercury deep underground, guided by natural or supernatural maturation over time, as articulated by scholars like Albertus Magnus in his 13th-century treatise De Mineralibus.^[18]^[19] In the 17th and 18th centuries, precursors to modern geology emerged with speculative models of Earth's interior, such as Athanasius Kircher's 1665 work Mundus Subterraneus, which proposed a vast network of subterranean caverns, rivers, and fires connecting volcanoes and explaining phenomena like earthquakes through a central infernal heat source. Similarly, Edmond Halley in 1692 suggested a hollow Earth model with concentric shells to account for magnetic variations, envisioning an inner luminous atmosphere and potentially habitable spaces within.^[20]^[21] These pre-modern concepts were fundamentally limited by their reliance on philosophical deduction and observation without empirical testing, portraying the geosphere as an eternal, unchanging entity shaped by divine or elemental principles rather than dynamic physical processes. This static worldview began to shift in the late 18th century toward empirical investigations that revealed Earth's dynamic nature.

Modern Scientific Formulation

The modern scientific formulation of the geosphere emerged in the 19th century, building on the principle of uniformitarianism advanced by James Hutton, who argued in his 1785 and 1795 works that Earth's geological features result from slow, ongoing processes rather than sudden catastrophes, and further developed by Charles Lyell in his 1830–1833 Principles of Geology, which emphasized that the present provides the key to understanding the past.^[22] This framework shifted geology toward empirical observation of Earth's solid components, laying groundwork for conceptualizing the geosphere as the planet's rocky interior and surface. The term "geosphere" itself was introduced in 1871 by Stephen Pearl Andrews in his book Primary Synopsis, referring to the solid portion of Earth as distinct from other realms, influenced by earlier notions like William E. Doherty's 1864 "geospheric realm."^[23] Eduard Suess advanced this, coining "lithosphere" in 1875 for the crust and "barysphere" in 1885 for the dense interior, framing Earth's solid parts in relation to the biosphere as a unified system shaped by gradual forces.^[24]^[23] In the early 20th century, seismological studies propelled the geosphere concept forward by unveiling its internal structure. Seismological studies in the early 20th century, using data from various earthquakes worldwide, enabled Richard Dixon Oldham to identify the core in 1906 through S-wave shadow zones, suggesting its liquid outer portion.^[25] Complementing this, Andrija Mohorovičić's 1909 analysis of regional earthquakes revealed a discontinuity (the Moho) separating the crust from the mantle, using P- and S-wave travel times to infer velocity changes.^[26] Alfred Wegener's 1912 presentation of continental drift theory to the German Geological Society introduced dynamism to the geosphere, proposing that continents move across the Earth's surface like rafts on a viscous layer, supported by fossil, rock, and paleoclimate evidence, though initially rejected for lacking a driving mechanism.^[27] The mid-20th century solidified the geosphere as a dynamic entity through the plate tectonics paradigm, which gained acceptance in the 1960s via evidence from seafloor spreading, magnetic striping, and earthquake distributions. Pioneering work by researchers like Harry Hess (1962) and J. Tuzo Wilson (1965) explained continental drift as rigid lithospheric plates moving over the asthenosphere, driven by mantle convection, unifying disparate geological observations into a cohesive model of the geosphere's behavior.^[28] In the 1970s and 1980s, this evolved into Earth system science, with NASA's Earth System Science Committee (formed 1983) outlining interactions among spheres in its 1986 report, and the International Geosphere-Biosphere Programme (launched 1987 by ICSU and UNESCO) formalizing the four-sphere model—atmosphere, hydrosphere, biosphere, and geosphere—to study global change holistically.^[29] Post-2000 formulations integrate advanced geophysics, defining the geosphere through models like the Preliminary Reference Earth Model (PREM), developed by Adam M. Dziewonski and Don L. Anderson in 1981 and widely used today for its radial profiles of density, seismic velocities (P- and S-waves), and attenuation, derived from earthquake data, free-oscillation spectra, and surface-wave dispersion.^[30] PREM underpins simulations of Earth's interior dynamics, such as convection and magnetic field generation, emphasizing the geosphere's role in planetary evolution and interactions with other spheres in climate models.^[31]

Internal Structure

Crust

The Earth's crust is the outermost solid shell of the planet, comprising a thin layer of rock that forms the surface upon which life exists. It is divided into two primary types: oceanic crust and continental crust. Oceanic crust, which underlies the ocean basins and covers about 70% of Earth's surface, is primarily basaltic in composition and typically 5-10 kilometers thick. In contrast, continental crust, which forms the continents and underlies them, is granitic in composition and thicker, ranging from 30 to 50 kilometers, with an average thickness of approximately 35 kilometers.^[32]^[12]^[33] The crust is predominantly composed of silicate minerals, including feldspar and quartz in continental regions, while oceanic areas feature denser mafic rocks like basalt. These materials originate from the partial melting of the underlying mantle: oceanic crust forms primarily at mid-ocean ridges where upwelling mantle material melts due to decompression, producing basaltic magma that solidifies into new crust; continental crust develops through more complex processes involving partial melting in subduction zones, where hydrated oceanic slabs trigger magma generation in the mantle wedge, leading to the creation of felsic rocks.^[34]^[35]^[36] A key feature defining the crust's lower boundary is the Mohorovičić discontinuity, or Moho, which separates the crust from the mantle and is detectable through seismic wave analysis. This boundary is marked by a sudden increase in P-wave velocity from 6-7 km/s in the crust to about 8 km/s in the mantle, reflecting the compositional shift from lighter crustal silicates to denser mantle peridotite.^[37]^[38] The crust has undergone continuous formation and recycling over approximately 4 billion years, driven by geological processes that renew oceanic material while preserving continental blocks. The oldest oceanic crust dates to about 200 million years ago, as older sections are subducted and recycled into the mantle; continental crust, however, contains rocks up to 4 billion years old, representing ancient stabilized portions that have resisted widespread destruction. This dynamic recycling underscores the crust's role as the mobile, uppermost layer in plate tectonics.^[39]^[40]^[41]

Mantle

The mantle is the thickest layer of Earth's interior, extending from the Mohorovičić discontinuity (Moho) at the base of the crust to the core-mantle boundary approximately 2,900 km below the surface, and comprising about 84% of Earth's total volume.^[42] It is divided into the upper mantle, which reaches depths of about 660 km and includes the ductile asthenosphere within its uppermost portion, and the lower mantle, which spans from 660 km to 2,900 km.^[42] This intermediate layer plays a central role in planetary dynamics, facilitating the slow movement of material that influences surface geology. The mantle's composition is dominated by silicate rocks, primarily peridotite, a dense ultramafic rock consisting mainly of olivine (approximately 40-90%) and pyroxene (5-50%), with minor amounts of garnet and spinel in deeper regions.^[43] As depth increases, high pressures induce phase transitions; notably, at around 660 km, the post-spinel transformation occurs, where ringwoodite (a high-pressure form of olivine) breaks down into bridgmanite (MgSiO3 perovskite) and magnesiowüstite, marking the onset of the lower mantle's mineralogy and contributing to seismic discontinuities.^[44] These changes reflect the mantle's response to extreme conditions, altering its density and rheological behavior without altering its overall chemical makeup. Despite being predominantly solid, the mantle exhibits ductile behavior due to elevated temperatures and pressures, allowing it to flow over geological timescales like a highly viscous fluid. Convection within the mantle is primarily driven by internal heat sources, including radioactive decay of elements like uranium, thorium, and potassium, as well as residual heat from Earth's formation and conduction from the core.^[45] Temperatures range from about 500°C near the top of the upper mantle to approximately 4,000°C at the base, while pressures escalate to 136 GPa at the core-mantle boundary.^[46]^[47] This convective circulation redistributes heat and material, powering processes like plate tectonics. Direct evidence for the mantle's structure and dynamics comes from seismic tomography, which images low-velocity zones interpreted as thermal plumes rising from the lower mantle and high-velocity regions corresponding to cold subducting slabs penetrating into the deep interior.^[48] Additionally, xenoliths—fragments of mantle rock entrained in volcanic eruptions—provide physical samples; for instance, peridotite nodules from alkali basalt and kimberlite volcanoes worldwide confirm the upper mantle's ultramafic composition and reveal metasomatic alterations from fluid interactions.^[49] These observations, combined with laboratory experiments on high-pressure minerals, underpin models of mantle convection and evolution.

Core

The Earth's core, the innermost layer of the geosphere, is divided into two distinct regions: a liquid outer core and a solid inner core. The outer core begins at a depth of approximately 2,900 km below the surface and extends to about 5,150 km, while the inner core occupies the central region from 5,150 km to the planet's center at 6,371 km. This structure accounts for roughly 16% of Earth's total volume but comprises about 32% of its mass, reflecting the core's high density and metallic nature.^[50]^[51]^[52] The core's composition is dominated by iron, which constitutes 85-90% of its mass, alloyed with approximately 5% nickel and lighter elements such as sulfur and oxygen that account for the remaining portion. These lighter elements lower the density compared to pure iron, resulting in an overall density gradient from about 10 g/cm³ in the outer core to 13 g/cm³ in the inner core. The metallic alloy enables electrical conductivity, crucial for the core's dynamic role in planetary processes.^[53]^[54]^[55] Key properties of the core include the convective motion of the molten outer core, which generates Earth's geomagnetic field through the geodynamo effect, where fluid movements sustain electric currents that produce magnetism. The inner core solidifies despite extreme temperatures of around 5,700°C, as the overlying pressure—reaching 330-360 GPa at the inner core boundary—exceeds the material's melting point under those conditions. Evidence for the outer core's liquidity comes from seismology, where shear (S) waves are absent in the shadow zone between 103° and 180° from earthquake epicenters, indicating a fluid medium that cannot transmit them. Additionally, paleomagnetic records preserved in rocks show geomagnetic field reversals occurring on average every 200,000 to 300,000 years, supporting the dynamo process driven by core convection. The latent heat from inner core solidification serves as a primary heat source for overlying mantle convection.^[56]^[57]^[58]^[59]^[50]

Key Geological Processes

Plate Tectonics

Plate tectonics is the theory that explains the movement and interaction of the Earth's lithospheric plates, which form the rigid outer shell of the planet. The lithosphere is divided into several major plates, including the African, Antarctic, Eurasian, Indian, Australian, North American, Pacific, and South American plates (with the Indian and Australian plates previously considered together as the Indo-Australian plate)—and numerous smaller minor plates. These plates float on the semi-fluid asthenosphere beneath and move at rates ranging from 1 to 10 centimeters per year, driven primarily by thermal convection currents in the mantle that transfer heat from the Earth's interior to the surface.^[60]^[61]^[62] The plates consist of the crust and the uppermost mantle, creating a brittle layer that can fracture and shift over time.^[63] Interactions at plate boundaries shape the geosphere through three primary types of motion. At divergent boundaries, plates pull apart, allowing magma to rise from the mantle and form new oceanic crust via rifting, as seen along the Mid-Atlantic Ridge where the Eurasian and North American plates are separating. Convergent boundaries occur where plates collide, with denser oceanic crust subducting beneath lighter continental crust or oceanic plates, leading to mountain building; the Himalayas exemplify this, formed by the ongoing convergence of the Indian and Eurasian plates at about 4-5 cm per year. Transform boundaries involve plates sliding laterally past each other along strike-slip faults, such as the San Andreas Fault in California, where the Pacific Plate moves northwest relative to the North American Plate.^[36]^[64]^[36] The driving forces behind plate motion include slab pull, ridge push, and mantle drag. Slab pull exerts the dominant force, accounting for roughly 80% of the total driving power, as the gravitational weight of cold, dense subducting slabs pulls the rest of the plate into the mantle. Ridge push contributes by the gravitational sliding of elevated mid-ocean ridges away from spreading centers, while mantle drag arises from viscous traction by underlying convection currents. These mechanisms are supported by direct evidence from Global Positioning System (GPS) measurements, which precisely track modern plate velocities, and paleomagnetic data showing symmetric striping on the seafloor—alternating bands of normal and reversed magnetic polarity in basaltic rocks—that record the rate of seafloor spreading over millions of years.^[65]^[36]^[66] Over hundreds of millions of years, plate tectonics has profoundly influenced the evolution of the geosphere by redistributing continents, oceans, and geological resources. For instance, the breakup of the Pangea supercontinent, which began around 200 million years ago, fragmented a single landmass into the modern continents through rifting and drift, altering global geography and concentrating mineral resources in specific regions tied to ancient plate positions. This dynamic process continues to govern the long-term configuration of Earth's surface features.^[67]

Endogenic and Exogenic Forces

Endogenic forces originate from within the Earth's interior, primarily driven by geothermal energy from radioactive decay and residual primordial heat, leading to vertical and horizontal movements that reshape the geosphere without necessarily involving large-scale plate motions.^[68] These processes include isostasy, which maintains gravitational equilibrium between the crust and mantle, causing uplift in response to load removal, such as post-glacial rebound observed in regions like Hudson Bay where current rates average 1-1.2 cm per year.^[69] Diapirism represents another key mechanism, where less dense materials like salt rise buoyantly through overlying denser rocks, forming structures such as salt domes that pierce sedimentary layers.^[70] Folding, induced by compressional stresses often associated with plate tectonics, deforms rock layers into anticlines and synclines on regional scales.^[71] In contrast, exogenic forces are powered by external energy sources, including solar radiation and gravity, acting on the Earth's surface to break down and transport materials. Weathering encompasses physical processes like frost action that fragment rocks and chemical processes such as hydrolysis that alter mineral compositions, preparing materials for removal.^[72] Erosion follows, with agents like rivers mobilizing and transporting sediment; globally, rivers deliver approximately 16-20 gigatons of sediment to oceans annually, sculpting valleys and lowering elevations over time.^[73] The interplay between endogenic and exogenic forces maintains a dynamic balance in geomorphic evolution, where internal uplift constructs landforms through processes like orogeny, while external denudation wears them down, achieving steady-state topography over geological timescales in many regions.^[74] This equilibrium ensures that average landscape relief remains relatively constant, as rates of tectonic elevation match erosion, preventing indefinite buildup or complete flattening.^[75] Representative examples include geysers, such as those in Yellowstone National Park, which manifest endogenic heat driving hydrothermal activity and episodic eruptions, and karst landscapes formed by exogenic chemical dissolution of soluble rocks like limestone, creating sinkholes and caves through groundwater action.^[76]

Interactions with Other Spheres

With Hydrosphere

The geosphere interacts extensively with the hydrosphere through physical and chemical processes driven by the hydrological cycle, where water acts as both an erosive agent and a solvent. Rivers and oceans erode continental rocks, transporting vast quantities of sediment to marine environments; for instance, global rivers deliver approximately 14 billion metric tons of suspended sediment to the oceans annually. This erosion reshapes landforms and contributes to the deposition of sediments on continental shelves and abyssal plains. Additionally, groundwater percolates through the geosphere, dissolving minerals from rocks and sediments to form aquifers; as water flows through fractures and pores, it acquires dissolved ions such as calcium, magnesium, and silica, increasing in mineral content with depth and residence time.^[77]^[78]^[79] Key physical processes at the geosphere-hydrosphere interface include submarine landslides and hydrothermal activity. Submarine landslides occur frequently along continental margins, where steep slopes and sediment accumulation lead to massive failures that displace water volumes capable of generating tsunamis; these events redistribute sediments across ocean basins and can cover up to 33% of some continental slopes. At mid-ocean ridges, hydrothermal vents facilitate high-temperature fluid circulation through newly formed basaltic crust, altering its mineralogy by precipitating sulfides and clays while leaching metals; this process affects the upper 500 meters of oceanic crust, influencing its permeability and composition over geological timescales.^[80]^[81]^[82] Geochemically, water-mediated weathering in the geosphere sequesters atmospheric CO₂ and releases essential nutrients to the hydrosphere. Silicate mineral hydrolysis, a primary reaction, consumes CO₂ to form stable carbonates; for example,

\text{CaSiO}_3 + 2\text{CO}_2 + 3\text{H}_2\text{O} \rightarrow \text{Ca}^{2+} + 2\text{HCO}_3^- + \text{H}_4\text{SiO}_4

followed by precipitation as CaCO₃, contributes to long-term global CO₂ drawdown estimated at 0.1–0.3 gigatons of carbon per year from continental weathering. This process also mobilizes nutrients like phosphorus and iron from rocks, which rivers transport to oceans, fueling phytoplankton productivity and supporting marine food webs. Oceanic sediments subducted at plate boundaries play a brief role in recycling these elements back into the geosphere.^[83]^[84]^[85]^[86] Illustrative examples highlight these interactions' scale and impacts. The Grand Canyon exemplifies prolonged fluvial erosion, carved by the Colorado River over approximately 6 million years into a 446-kilometer-long chasm up to 1.8 kilometers deep, exposing 2-billion-year-old rocks through persistent downcutting and sediment transport. Similarly, geospheric displacements like underwater landslides or earthquakes generate tsunamis by rapidly displacing seawater, as seen in events where slope failures produce waves exceeding 10 meters in height near continental margins.^[87]^[88]

With Atmosphere

The geosphere interacts with the atmosphere through gas-solid processes that influence both geochemical cycles and climate dynamics. Atmospheric gases such as carbon dioxide (CO₂) and oxygen (O₂) drive chemical weathering of rock minerals, where CO₂ dissolves in rainwater to form carbonic acid, accelerating the breakdown of silicates and carbonates.^[89] Similarly, O₂ facilitates oxidation reactions, notably the rusting of iron-bearing minerals like those in basalts and granites, which alters rock composition and releases ions into the environment. These interactions contribute to the long-term regulation of atmospheric composition by sequestering gases into solid forms over geological timescales.^[90] Acid rain, with a typical pH of 4.2–4.4 due to anthropogenic pollutants like sulfur dioxide and nitrogen oxides, further intensifies mineral dissolution in the geosphere. This acidity enhances the weathering rate of carbonate rocks such as limestone, leading to increased erosion and the release of calcium and other cations that can influence atmospheric alkalinity.^[91] In contrast to natural rainwater (pH ~5.6), acid rain's lower pH promotes faster chemical reactions, amplifying the geosphere's role in buffering atmospheric acidity.^[92] Volcanism represents a direct geospheric input to the atmosphere, with global eruptions emitting approximately 23 Tg of SO₂ annually from passive degassing and explosive events. This SO₂ oxidizes to form sulfate aerosols in the stratosphere, which reflect incoming solar radiation and induce temporary global cooling.^[93] A prominent example is the 1815 Mount Tambora eruption, which injected massive SO₂ volumes, resulting in a global temperature drop of about 0.5°C and the "Year Without a Summer" in 1816. Such events highlight the geosphere's capacity to modulate short-term climate variability through aerosol forcing.^[93] The geosphere serves as the largest reservoir of carbon on Earth, storing approximately 65,000,000 Gt of carbon primarily in sedimentary rocks like limestone and shale.^[89] Silicate weathering links this reservoir to the atmosphere by consuming CO₂ over millions of years: rainwater carbonic acid reacts with silicate minerals (e.g., in feldspars), forming bicarbonate ions that are transported to oceans and eventually deposited as carbonates, thus regulating long-term atmospheric CO₂ levels and stabilizing climate.^[83] This feedback mechanism has maintained Earth's habitability by counteracting volcanic CO₂ outgassing.^[94] Dust storms exemplify aerial transport of geospheric materials, mobilizing 1–2 Gt of mineral aerosols annually from arid regions like the Sahara and Gobi deserts.^[95] These particles, primarily silicates and clays, are lofted into the atmosphere by winds, affecting air quality through deposition of fine particulates that can exacerbate respiratory issues in downwind areas. Additionally, mineral dust fertilizes distant ecosystems by supplying trace nutrients like iron, influencing atmospheric chemistry via heterogeneous reactions that alter ozone and aerosol lifetimes.^[96]

With Biosphere

The biosphere exerts profound influence on the geosphere through organism-mediated processes that drive rock disintegration, soil development, and elemental exchanges, fundamentally shaping Earth's solid surface over both short and long timescales. These interactions highlight the interconnectedness of life and lithosphere, where biological activity accelerates geochemical transformations that would otherwise proceed far more slowly. For instance, bioweathering and pedogenesis not only modify the geosphere's composition but also facilitate nutrient availability essential for sustaining ecosystems. Bioweathering represents a primary mechanism by which the biosphere degrades the geosphere, with microorganisms and plants enhancing both physical and chemical breakdown of bedrock. Lichens colonize rock surfaces and secrete organic acids, such as oxalic acid, which chelate cations and dissolve minerals, thereby accelerating weathering rates to approximately 0.1–1 mm of rock per year in suitable environments. Plant roots further contribute by exerting mechanical pressure as they expand into fractures, physically fracturing bedrock and widening cracks to depths exceeding 180 cm, as observed in shale formations where roots exploit pre-existing fissures for anchorage and resource access. These processes collectively weaken the geosphere's structural integrity, promoting the transition from solid rock to weathered regolith. Soil pedogenesis, the formation and evolution of soil profiles, relies heavily on biospheric inputs to create the pedosphere as a dynamic interface between geosphere and life. Decomposing plant and microbial biomass supplies organic matter that binds mineral particles, fostering aggregation and nutrient retention in fertile topsoil layers essential for terrestrial ecosystems. Soil fauna, particularly earthworms, intensify this by bioturbating the substrate; in temperate grasslands and forests, they can process and mix 20–50 tons of soil per hectare annually through burrowing and casting, improving aeration, drainage, and organic incorporation while redistributing minerals vertically. Biogeochemical cycling underscores the reciprocal exchange between spheres, with the geosphere providing bioessential elements whose availability modulates biospheric productivity. Phosphorus, primarily sourced from the chemical weathering of apatite in igneous and sedimentary rocks, exemplifies this linkage, as its slow release often limits net primary productivity in roughly 40% of global terrestrial ecosystems by constraining plant growth and microbial activity. This limitation shapes community structures and carbon fluxes, reinforcing the geosphere's role as a nutrient reservoir. On longer timescales, the biosphere's legacy imprints the geosphere through preserved organic deposits and ecological upheavals. Fossil fuels—coal, oil, and natural gas—derive from ancient photosynthetic biomass buried and lithified over millions of years, representing compressed remnants of prehistoric ecosystems that, when mined, expose and disrupt underlying stratigraphic layers, leading to landscape destabilization and erosion in extraction sites. Mass extinctions amplify these effects; the Cretaceous–Paleogene event, which eradicated non-avian dinosaurs, triggered vegetation shifts that re-engineered fluvial systems, resulting in wider, more sinuous rivers and expansive floodplains as mammalian herbivores and angiosperm dominance altered sediment dynamics and erosion patterns. Biological weathering also briefly aids atmospheric CO2 drawdown by amplifying silicate dissolution, converting CO2 into stable bicarbonate in runoff.

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Eduard Suess (1831-1914) is probably the greatest geologist who ever lived. He died 100 years ago and left us the modern geology as we know it. His work.
[26]
[PDF] Seismology and the Earth's Interior - Stanford University
Figure 18-8. The earthquake of 1906 was caused by slip along the. San Andreas fault. The offset fence shown here shows a slip of nearly 3 m. The scene is near ...
[27]
Oldham and Mohorovičić Determine the Earth's Interior Structure
Richard Dixon Oldham, Andrija Mohorovi Mohorovičić, and other seismologists, using data from earthquakes, revealed the layered internal structure of the earth.
[28]
Alfred Lothar Wegener [This Dynamic Earth, USGS]
Jul 11, 2025 · Tenacious by nature, Wegener spent much of his adult life vigorously defending his theory of continental drift, which was severely attacked ...
[29]
Plate Tectonic Theory: A Brief History - IRIS
This animation gives an overview of the most-recognized proponents (and opponents) of Plate Tectonics Theory up into the 1960's.
[30]
Earth system science - Wikipedia
Earth system science assumes a holistic view of the dynamic interaction between the Earth's spheres and their many constituent subsystems fluxes and processes.
[31]
Earth System Approach
Feb 6, 2006 · Since about 1980, an important paradigm has emerged in the geosciences, analogous to the plate tectonics revolution of the 1950s and 1960s.
[32]
[PDF] Preliminary reference Earth model * - Harvard University
The Preliminary Reference Earth Model, PREM, and auxiliary tables showing fits to the data are presented. Preamble and his models A and B were employed exten-.Missing: post- | Show results with:post-
[33]
Once Again on Preliminary Reference Earth Model - Guliyev - 2020
Jan 28, 2020 · We studied the isotropic ball using data of Preliminary Reference Earth Model (PREM). It is shown that such a ball should be either ...Missing: post- | Show results with:post-
[34]
The Oceanic Crust and Seafloor - University of Hawaii at Manoa
The oceanic crust is much thinner, ranging from 5 to 10 km thick. The continental crust has an average density of 2.7 g/cm3 and is composed primarily of felsic ...Missing: definition | Show results with:definition
[35]
[PDF] Lecture 34 - SOEST Hawaii
By area, oceanic crust is more abundant: oceanic: ~7 km average thickness. ~2/3 earth's surface continental: ~35 km average thickness. ~1/3 earth's surface.
[36]
Minerals – Introduction to Earth Science - Pressbooks at Virginia Tech
Quartz and feldspar are the two most abundant minerals in the continental crust. ... In fact, feldspar itself is the single most abundant mineral in the Earth's ...<|control11|><|separator|>
[37]
[PDF] Igneous Rocks - West Virginia Geological and Economic Survey
Earth's brittle oceanic crust is primarily composed of basalt while the brittle continental crust is mainly granite (Figure 1). Most of Earth's upper mantle is ...
[38]
Understanding plate motions [This Dynamic Earth, USGS]
Jul 11, 2025 · Divergent boundaries occur along spreading centers where plates are moving apart and new crust is created by magma pushing up from the mantle.
[39]
Layers of the Earth—What is the Moho? - Animation - IRIS
The Mohorovicic Discontinuity, commonly called the “Moho” is recognized as the boundary zone between Earth's crust and the mantle. This boundary marks a change ...
[40]
[PDF] Theory of the Earth - Caltech Authors
It separates rocks having P-wave velocities of 6-7 km/s from those having velocities of about 8 km/s.
[41]
Before the break-up of Pangaea [This Dynamic Earth, USGS]
Jul 11, 2025 · This is because the average age of the present-day oceanic crust is about 55 million years; the oldest parts are about 180 million years old, ...
[42]
[PDF] Continental Crust And Oceanic Crust
This results in oceanic crust that is relatively young, typically less than 200 million years old due to the constant recycling via subduction zones.
[43]
[PDF] Continent formation through time - LSU Scholarly Repository
The continental crust is also far more ancient than the oceanic crust. The oldest areas of continental crust are c. 4 Ga old with single zircon crystals as ...
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Mantle - National Geographic Education
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[45]
[PDF] Structure and Composition of the Mantle
The mantle has an ultrabasic composition; the compositional boundary between the crust and mantle is the Mohorovicic seismic discontinuity (the Moho). The ...
[46]
Complete agreement of the post-spinel transition with the 660-km ...
Apr 20, 2018 · We present new experimental data showing post-spinel transition pressures in complete agreement with the 660-km discontinuity depth.
[47]
3.3 Earth's Interior Heat – Physical Geology – H5P Edition
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[48]
Earth's Layers: Crust, Mantle & Core, Seismic Discontinuities
The crust is a silicate solid, the mantle is a viscous molten rock, the outer core is a viscous liquid, and the inner core is a dense solid. Watch video for ...
[49]
How lowermost mantle viscosity controls the chemical structure of ...
Dec 19, 2023 · This results in a pressure of 136 GPa at the CMB. Near the CMB, the initial temperature is superadiabatic in a thin thermal boundary layer ...
[50]
Mantle plume tomography - ScienceDirect.com
We review the resolution currently available with seismic tomography, in particular the ability of seismic waves to image mantle plumes.
[51]
[PDF] Mafic and Ultramafic Xenoliths from Volcanic Rocks of the Western ...
This document is about mafic and ultramafic xenoliths from volcanic rocks of the Western United States, and is a US Geological Survey Professional Paper.
[52]
The Interior of the Earth - USGS Publications Warehouse
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[53]
3-D Earth Structure Model - Purdue University
The core is ~16.5% of the Earth by volume but about 33% of the Earth by mass. No seismic shear waves travel in outer core. Convection currents in the ...<|control11|><|separator|>
[54]
[PDF] Lecture 9: The Earth and What's Inside
The core represents 32.5% of the Earth's mass. Scientists believe it is mostly iron-nickel alloy, although they do not know very much about the properties of ...
[55]
Journey to the center of the earth: exploring iron's equation of state
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[56]
A seismologically consistent compositional model of Earth's core - NIH
It is well known that Earth's core is made primarily of iron, alloyed with ∼5% nickel and some lighter elements, such as carbon, oxygen, silicon, or sulfur.
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Structure of the Earth - HyperPhysics
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[58]
How does the Earth's core generate a magnetic field? - USGS.gov
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[59]
The melting curve of iron to 250 gigapascals
The melting temperature of iron at the pressure of the core-mantle boundary (136 GPa) is 4800 + or - 200 K, whereas at the inner core-outer core boundary (330 ...
[60]
Seismic Shadow Zones: S wave shadow zone - IRIS
How do S waves give evidence for a liquid outer core? A seismic shadow zone is an area of the Earth's surface where seismographs cannot detect an earthquake ...
[61]
Is it true that Earth's magnetic field occasionally reverses its polarity?
Yes. We can see evidence of magnetic polarity reversals by examining the geologic record. When lavas or sediments solidify, they often preserve a signature ...
[62]
What is a Plate? - The Geological Society
The surface of the Earth is divided into 7 major and 8 minor plates. The largest plates are the Antarctic, Eurasian, and North American plates.
[63]
How fast do tectonic plates move? | U.S. Geological Survey
Tectonic plates move roughly at the same rate as fingernails grow, but at different speeds and directions, measured within a fraction of a millimeter per year.
[64]
Some unanswered questions [This Dynamic Earth, USGS]
Jul 11, 2025 · Scientists generally agree with Harry Hess' theory that the plate-driving force is the slow movement of hot, softened mantle that lies below the rigid plates.
[65]
What is a tectonic plate? [This Dynamic Earth, USGS]
Jul 11, 2025 · A tectonic plate is a massive, irregularly shaped slab of solid rock, composed of both continental and oceanic lithosphere.
[66]
The Himalayas: Two Continents Collide
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[67]
Geological archive of the onset of plate tectonics - Journals
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Developing the theory [This Dynamic Earth, USGS]
Jul 11, 2025 · When these magnetic patterns were mapped over a wide region, the ocean floor showed a zebra-like pattern. Alternating stripes of magnetically ...<|control11|><|separator|>
[69]
Historical perspective [This Dynamic Earth, USGS]
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Geomorphic Processes: Endogenic and Exogenic Forces in Earth ...
Sep 28, 2025 · The primary energy source for endogenic processes is geothermal energy, generated by radioactivity and primordial heat. Variations in geothermal ...
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Isostasy: A lithospheric balancing act - Geological Digressions
Jan 22, 2021 · Initial rebound (uplift) rates were as high as 8-9 m/100 years; present rates average 1-1.2 m/100 years – rates that even today are ...
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Diapirism - an overview | ScienceDirect Topics
Diapirism underlying less dense rock rises through buoyant forces. Diapirs (Fig. 4.15) are most commonly composed of evaporatic salt deposits (salt domes) ...
[73]
Folding and Faulting - University of Hawaii System
When endogenic forces squeeze rock in compression, it does not immediately fracture, but deforms extremely slowly. Because it can deform without breaking ...
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Weathering - National Geographic Education
Jun 5, 2025 · Once a rock has been broken down, a process called erosion transports the bits of rock and minerals away. Water, acids, salt, plants, animals ...
[75]
Spatial Trends and Drivers of Bedload and Suspended Sediment ...
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[76]
[PDF] Introduction to Geomorphic Principles
Mass Balance: Endogenic vs. Exogenic Processes. 1. Thus exists a balance between crustal uplift (endogenic) and crustal denudation. (exogenic) in the form of ...
[77]
Landscape evolution space and the relative importance of ...
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Karst Landscapes - Caves and Karst (U.S. National Park Service)
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World-Wide Delivery of River Sediment to the Oceans
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Groundwater | Dissolved mineral sources and significance - NGWA
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Sources of Dissolved Solids in Brackish Groundwater - USGS.gov
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[82]
Large Submarine Landslides on Continental Slopes: Geohazards ...
Oct 2, 2015 · Submarine landslides on open continental slopes can be prodigious in scale. They are an important process for global sediment fluxes, ...
[83]
Morphology of late Quaternary submarine landslides along the U.S. ...
They cover 33% of the continental slope and rise of the glacially influenced New England margin, 16% of the sea floor offshore of the fluvially dominated Middle ...
[84]
Effect of paleoseawater composition on hydrothermal exchange in ...
Nov 6, 2017 · Circulation of seawater through midocean ridges results in large-scale chemical transfer between the solid Earth and oceans.
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Global CO2 Consumption by Silicate Rock Chemical Weathering: Its ...
Apr 20, 2021 · Silicate rock weathering maintains a stable and long-term absorption of CO2. However, the magnitude, spatial pattern, and evolution ...
[86]
[PDF] The importance of terrestrial weathering changes in multimillennial ...
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Phosphorus and Life on a Water World - Filippelli - AGU Journals
Apr 1, 2022 · An adequate amount of phosphorus can be weathered rom seafloor basalts in anoxic settings to supply biological productivity and support a long-lived ecosystem.
[88]
The Role of Sediment Accretion and Buoyancy on Subduction ...
Oct 13, 2021 · Subducted sediments are thought to lubricate the subduction interface and promote faster plate speeds. However, global observations are not ...
[89]
Geology - Grand Canyon National Park (U.S. National Park Service)
Scientists know that the Colorado River carved Grand Canyon. The river is thus slightly older than the canyon, though the two are certainly close in age.
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How do landslides cause tsunamis? | U.S. Geological Survey
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The Carbon Cycle - NASA Earth Observatory
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[PDF] Chapter 13 CHEMICAL WEATHERING AND ITS EFFECT ON ...
During the weathering of silicate and carbonate minerals atmospheric. CO2 is taken up and converted to dissolved HCO3" in natural waters. The HCO3", after.
[93]
Acid Rain and Water | U.S. Geological Survey - USGS.gov
How does acid precipitation affect marble and limestone buildings? Acid precipitation affects stone primarily in two ways: dissolution and alteration. When ...
[94]
Effects of Acid Rain | US EPA
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[95]
Volcanoes Can Affect Climate | U.S. Geological Survey - USGS.gov
Yearly CO2 emitters, Billion metric tons per year (Gt/y) ; Global volcanic emissions (highest preferred estimate), 0.26 ; Anthropogenic CO2 from fuel combustion ...
[96]
How temperature-dependent silicate weathering acts as Earth's ...
Jan 26, 2023 · Silicate minerals solubilize CO2 from the atmosphere during weathering and release charged DIC species as the minerals release aqueous base ...
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Sand and dust storms - World Meteorological Organization WMO
Sand and dust storms (SDS) occur when strong winds lift sand and dust from dry soils into the atmosphere, transporting particles over vast distances.Missing: mineral Gt
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Mineral dust: An overview | Request PDF - ResearchGate
Aug 7, 2025 · It has been estimated that the 1990s global annual mineral dust emissions were of the order of 1490±160 Tg yr Mineral dust comes from a wide ...