Peter Haff

• Duke University

The Anthropocene as a prospective new, ongoing series/epoch must be defensible against all relevant concerns. We address the seven, still-relevant challenges posed to the Anthropocene Working Group by the Chair, International Commission on Stratigraphy (ICS), in 2014. (1) Concept or reality? The Anthropocene possesses a substantial, sharply distinc...

Merritts et al. (2023) misrepresent Paul Crutzen’s Anthropocene concept as encompassing all significant anthropogenic impacts, extending back many millennia. Crutzen’s definition reflects massively enhanced, much more recent human impacts that transformed the Earth System away from the stability of Holocene conditions. His concept of an epoch (henc...

The technosphere, the interlinked network of the world’s humans and technological artefacts, is the defining structure of the Anthropocene. The technosphere is undesigned, autonomous and possesses agency. Where influenced by human knowledge, its future behaviour is unpredictable, although constrained by generic principles of organization. Humans fa...

Event stratigraphy is used to help characterise the Anthropocene as a chronostratigraphic concept, based on analogous deep-time events, for which we provide a novel categorization. Events in stratigraphy are distinct from extensive, time-transgressive ‘episodes’ – such as the global, highly diachronous record of anthropogenic change, termed here an...

Event stratigraphy is used to help characterise the Anthropocene as a chronostratigraphic concept, based on analogous deep-time events, for which we provide a novel categorization. Events in stratigraphy are distinct from extensive, time-transgressive ‘episodes’ – such as the global, highly diachronous record of anthropogenic change, termed here an...

Event stratigraphy is used to help characterise the Anthropocene as a chronostratigraphic concept, based on analogous deep-time events, for which we provide a novel categorization. Events in stratigraphy are distinct from extensive, time-transgressive ‘episodes’ – such as the global, highly diachronous record of anthropogenic change, termed here an...

The extensive array of mid-20 th century stratigraphic event signals associated with the 'Great Acceleration' enables precise and unambiguous recognition of the Anthropocene as an epoch/series within the Geological Time Scale. A mid-20 th century inception is consistent with Earth System science analysis in which the Anthropocene term and concept a...

The Anthropocene defined as an epoch/series within the Geological Time Scale, and with an isochronous inception in the mid-20th century, would both utilize the rich array of stratigraphic signals associated with the Great Acceleration and align with Earth System science analysis from where the term Anthropocene originated. It would be stratigraphic...

We analyse the ‘three flaws’ to potentially defining a formal Anthropocene geological time unit as advanced by Ruddiman (2018). (1) We recognize a long record of pre-industrial human impacts, but note that these increased in relative magnitude slowly and were strongly time-transgressive by comparison with the extraordinarily rapid, novel and near-g...

We analyse the ‘three flaws’ to potentially defining a formal Anthropocene geological time unit as advanced by Ruddiman (2018). (1) We recognize a long record of pre-industrial human impacts, but note that these increased in relative magnitude slowly and were strongly time-transgressive by comparison with the extraordinarily rapid, novel and near-g...

The Anthropocene, a term launched into public debate by Nobel Prize winner Paul Crutzen, has been used informally to describe the time period during which human actions have had a drastic effect on the Earth and its ecosystems. This book presents evidence for defining the Anthropocene as a geological epoch, written by the high-profile international...

This essay aims to show how what is most intimately and essentially human – our ideas, personal purposes, feelings, and dreams – finds space for expression within the autonomous, unfeeling, physical dynamics of the technosphere – the defining system of the Anthropocene. The approach adopted is based on systems science and aims to avoid metaphysical...

This is the link to the press release from University of Leicester for the new AWG paper authored by the above members of the working group: https://www2.le.ac.uk/offices/press/press-releases/2017/march/the-anthropocene-scientists-respond-to-criticisms-of-a-new-geological-epoch

A range of published arguments against formalizing the Anthropocene as a geological time unit have variously suggested that it is a misleading term of non-stratigraphic origin and usage, is based on insignificant temporal and material stratigraphic content unlike that used to define older geological time units, is focused on observation of human hi...

We assess the scale and extent of the physical technosphere, defined here as the summed material output of the contemporary human enterprise. It includes active urban, agricultural and marine components, used to sustain energy and material flow for current human life, and a growing residue layer, currently only in small part recycled back into the...

The dynamics of the modern Earth-system is not explicable without reference to systems that have a purpose, i.e., that exhibit goal-seeking behavior. This paper develops the physical basis of agency or purposiveness in the technosphere-the human-technological system that defines the Anthropocene-as part of an analysis of the organizational requirem...

Biospheric relationships between production and consumption of biomass have been resilient to changes in the Earth system over billions of years. This relationship has increased in its complexity, from localised ecosystems predicated on anaerobic microbial production and consumption, to a global biosphere founded on primary production from oxygenic...

Across a large proportion of Earth’s ice-free land surfaces, a solid-phase stratigraphic boundary marks the division between humanly modified ground and natural geological deposits. At its clearest, the division takes the form of an abrupt surface at the base of deposits variously called ‘artificial ground’, ‘anthropogenic ground’ or ‘archaeologica...

We evaluate the boundary of the Anthropocene geological time interval as an epoch, since it is useful to have a consistent temporal definition for this increasingly used unit, whether the presently informal term is eventually formalized or not. Of the three main levels suggested e an ‘early Anthropocene’ level some thousands of years ago; the begin...

The dominant mode of entropy production enabled by the large-scale technological systems that power the world economy is the degradation of chemical energy in fossil fuels. One key parameter determining the rates of fossil fuel consumption and entropy production is the price of energy. The Rayleigh-Benard cell provides a laboratory analog in which,...

Humans play an essential role in creating the technological systems of the Anthropocene, but, nonetheless, large-scale technology – the ‘technosphere’ – operates according to a quasi-autonomous dynamics, summarized by six rules: (1) the rule of inaccessibility, that large components of the technosphere cannot directly influence the behavior of thei...

The technosphere, the interlinked set of communication, transportation, bureaucratic and other systems that act to metabolize fossil fuels and other energy resources, is considered to be an emerging global paradigm, with similarities to the lithosphere, atmosphere, hydrosphere and biosphere. The technosphere is of global extent, exhibits large-scal...

Certain desert surfaces called desert pavements are characterized by a nearly stone-free layer of fine granular material, mostly silt (diameter of hundredths of mm) and sand (tenths of mm) capped by a monolayer of pebble-sized (few cm) stones. The fine granular material is deposited as dust from the air, so the stones must be levitated to accommoda...

As humans have colonised and modified the Earth’s surface, they have developed progressively more sophisticated tools and technologies. These underpin a new kind of stratigraphy, that we term technostratigraphy, marked by the geologically accelerated evolution and diversification of technofossils – the preservable material remains of the technosphe...

As humans become increasingly dominant agents of geologic change, prediction of the reaction of natural systems to human intervention and of the performance of geoengineered structures assumes increasing importance. To help clarify the role of geological prediction in an anthropic world, we examine the end-member cases of prediction in natural geol...

Displacement of mass of limited deformability ("solids") on the Earth's surface is opposed by friction and (the analog of) form resistance - impediments relaxed by rotational motion, self-powering of mass units, and transport infrastructure. These features of solids transport first evolved in the biosphere prior to the emergence of technology, allo...

We provide a probabilistic definition of the bed load sediment flux. In treating particle positions and motions as stochastic quantities, a flux form of the Master equation (a general expression of conservation) reveals that the volumetric flux involves an advective part equal to the product of an average particle velocity and the particle activity...

Displacement of mass of limited deformability ("solids") on the Earth's surface is opposed by friction and (the analog of) form resistance - impediments relaxed by rotational motion, self-powering of mass units, and transport infrastructure. These features of solids transport first evolved in the biosphere prior to the emergence of technology, allo...

We provide a concise, probabilistic definition of the bed load sediment flux. In treating particle positions and motions as stochastic quantities, a flux form of the Master Equation reveals that the volumetric flux involves an advective part equal to the product of an average particle velocity and the particle activity (the solid volume of particle...

We analyzed bedload transport through detailed spatial-temporal mapping of sand grains from high-speed images taken during flume experiments. These experiments involved four different average fluid velocities. We tracked individual particles at a time resolution of 1/25th of a second over a total of four seconds for each average fluid velocity. Vir...

The surface of the earth is being transformed by a new force in the form of technological systems and processes that move significant quantities of mass large distances. Because movement of mass is perhaps the most basic geomorphic process, and because the continuing rise of technology appears to characterize a new epoch in earth evolution (the Ant...

In soil-mantled steeplands, soil motions associated with creep, ravel, rain splash, soil slips, tree throw, and rodent activity are patchy and intermittent and involve widely varying travel distances. To describe the collective effect of these motions, we formulate a nonlocal expression for the soil flux. This probabilistic formulation involves ups...

We live in the Anthropocene: For better or for worse, the Earth system now functions in ways unpredictable without understanding how human systems function and how they interact with and control Earth system processes. Regardless of whether this transition from the Holocene (generally thought of as the past 12,000 years) to the new epoch of the Ant...

1] For hillslopes undergoing ''diffusive'' soil transport, it is often assumed that the soil flux is proportional to the local land-surface gradient, where the coefficient of proportionality is like a diffusion coefficient. Inasmuch as transport involves quasi-random soil particle motions related to biomechanical mixing and similar dilational proce...

We formulate soil grain transport by rain splash as a stochastic advection-dispersion process. By taking into account the intermittency of grain motions activated by raindrop impacts, the formulation indicates that gradients in raindrop intensity, and thus grain activity (the volume of grains in motion per unit area) can be as important as gradient...

It just doesn't add up.

The following is a white paper (adapted here for print) for the U.S. National Research Council's committee on Challenges and Opportunities in Earth Surface Processes, drafted at a National Science Foundation sponsored workshop associated with the 38th Binghamton Geomorphology Symposium, “Complexity in Geomorphology,” held at Duke University in Octo...

We formulate soil grain transport by rainsplash as a stochastic advection-dispersion process. By taking into account the intermittency of grain motions activated by raindrop impacts, the formulation indicates that gradients in raindrop intensity, and thus grain activity, can be as important as gradients in grain concentration and surface slope in e...

An analogy between turbulent fluid systems and landscape drainage systems [Parker, G., Haff, P.K., Murray, A.B., 2001, EOS, Transactions of the American Geophysical Union, 82, pp. F564.] is suggested by the observation that transport in both systems can be approximated by diffusion with size-proportional effective diffusivities, with a cross-over a...

Conservation should benefit ecosystems, nonhuman organisms, and current and future human beings. Nevertheless, tension among these goals engenders potential ethical conflicts: conservationists' true motivations may differ from the justifications they offer for their activities, and conservation projects have the potential to disempower and oppress...

Sediment erosion laws form the basis for most landscape evolution models and guide geomorphologists in the pursuit of understanding how landscapes evolve. This focus on the alluvial surface, however, ignores the role of intrinsic feedbacks between sediment transport and bedrock weathering in shaping Earth's landforms. Here, we present a new, p...

We present model results suggesting that a physical erosion–bedrock weathering feedback is responsible for the development of isolated bedrock knobs (tors/inselbergs) that often punctuate otherwise smooth pediments of homogeneous basement lithology. Tors and larger, more heavily jointed and morphologically complex exposures, inselbergs, may arise a...

Sediment transport by wind is one of many processes of interest to the geomorphologist in which grain to grain contacts play an important role. In order to illustrate the modelling of collections of frictional, inelastic sedimentary grains with the particle dynamics method (PDM), we use the grain impact process in aeolian saltation as a specific ex...

Coupled equations of motion for steady state saltation over an infinite plane are derived and solved for a simplified model of the grain-surface impact process. Experimentally observed features of the wind velocity profile in saltation are qualitatively reproduced, including a diminution of the sub-saltation layer mean wind speed, as the friction s...

ABSTRACTA critical event in the trajectory of a sand grain saltating in air is its interaction with the surface. We examine the phenomenon of grain-bed impacts in two dimensions using a combination of dynamical computer simulations, analytical models and physical reasoning. The results indicate that the grain-bed collisions can be treated as two-bo...

We previously developed a numerical model to explain the origin and maintenance of a) laterally extensive (km`s), planar bedrock pediments of low slope covered by a nearly uniformly thin regolith blanket, b) bare-bedrock or boulder pile edifices (tors and `inselbergs’), and c) the piedmont junction, a sharp slope discontinuity that often demarcates...

The October 1999 Mw 7.1 Hector Mine earthquake in the Mojave Desert, California, generated characteristic surface disturbances on nearby desert pavements. These disturbances included (1) zones of wholesale gravel displacement interspersed with zones of intact pavement, (2) displaced and rotated cobbles, (3) moats around loosened, embedded boulders,...

We previously developed a model that incorporates a feedback between bedrock weathering and physical erosion (stream flow and diffusive processes) to explain the origin and maintenance of the laterally extensive (km’s), nearly uniformly thin regolith blanket that characterizes pediments in arid regions such as the southwestern United States. Specif...

Although widely disseminated throughout many different climatic environments, pediments, or gently sloping, laterally extensive surfaces characterized by a thin veneer of alluvium covering bedrock, are particularly well developed in granitic desert locales such as the Mojave and Colorado Deserts in southern California and the Sonoran Desert in west...

The surface of the earth is undergoing profound change due to human impact. By some measures the level of human impact is comparable to the effects of major classical geomorphic processes such as fluvial sediment transport. This change is occurring rapidly, has no geologic precedent, and may represent an irreversible transition to a new and novel l...

We live at a time when the surface of the Earth, as represented by its soils, vegetation, streams, and topography, is being radically transformed by human activity. The change is global and rapid (occurring on human time scales). Periods of change provide opportunity for science, and the present time is no exception for the opportunities it offers...

Ongoing disruption of ancient, varnished desert pavement surfaces near Death Valley National Park is inferred to be the result of unusually intense animal foraging activity. Increased levels of bioturbation are associated with enhanced vegetation growth stimulated by recent El Nino precipitation. The occurrence of abundant, recently overturned, var...

The dendritic structure of fluvial drainage networks is a fascinating problem in morphodynamics. In recent years it has become possible to implement numerical models in which drainage networks self-evolve in response to relatively simple local laws so as to yield a fractal "cover" of the catchment. Such models are, however, incapable of capturing a...

Waterbots are elements of a landscape evolution model based on discrete units of runoff that are able to pick up and deposit sediment. The waterbot model is a cellular automaton model (Toffoli and Margolus, 1989) that captures much of the essence of more detailed hydrologic models. Waterbots are similar to the precipitons introduced by Chase (Chase...

The long-standing problem of explaining metabolic scaling in animals, whereby whole-animal metabolic rate B is observed to increase as a function of body mass M approximately as M3/4, has been recently revisited by Banavar et al. (see also ref. 3, in which allometric scaling rules are derived from fractal geometry). These authors derive and general...

The principal goal of the present study has been to construct and test computer algorithms for fluvial sediment erosion and deposition processes. Real-life topographic features in arid terrain have been used as a source of groundtruth information. Much use is being made today of generic landscape evolution models. But little effort has gone into te...

Diffusion of topography is normally considered a smoothing process, but at the scale of the diffusive disturbance, diffusion becomes a roughening process. Roughening is exemplified by topographic features associated with disturbances such as animal burrows, hoof prints of grazing animals, and small landslides (here called large-scale processes). Di...

Mature desert pavements are traditionally regarded as hallmarks of stability, but their stability is dynamic, not static. In a study aimed at documenting this dynamic stability and its role in healing surface disturbances, experiments were performed over a 5-yr period on small cleared patches, or plats, on pavement surfaces in Panamint Valley, Cali...

Sources of uncertainty or error that arise in attempting to scale up the results of laboratory-scale sediment transport studies for predictive modeling of geomorphic systems include: (i) model imperfection, (ii) omission of important processes, (iii) lack of knowledge of initial conditions, (iv) sensitivity to initial conditions, (v) unresolved het...

Rates and directions of motion have been determined for 19 barchan dunes near the Salton Sea, California, for the period 1941 to 1981. Between 1941 and 1956 these barchans moved with an average speed of 15.5 m y⁻¹ in the direction 89° T (T = from true north). During the period 1956–1963 the rate of motion increased to 24.4 m y⁻¹, and the direction...

The partial differential equation (PDE) is often the tool of choice for describing the behavior of complicated fluid or solid mechanical systems. Sometimes, however, mechanical systems are composed of physically distinct elements that are not so large in number that a continuum description of the entire system is feasible or possible, or, although...

We present two examples of micromechanical simulations and show how the calculations can be used to draw useful conclusions at the macroscopic leve. In bedload transport by water we examine the mixing depth of sediments undergoing shear traction. In transport of dry sand grains by wind we examine the development of periodic bedforms and the burial...

We solve the Newtonian equations of motion to follow the trajectories of each of a large number of two-dimensional circular bed load particles as they move in response to stresses exerted by an overlying fluid. The fluid is modeled as a moving layer or ``slab'' which exerts a velocity-dependent drag force on embedded particles and satisfies its own...

The PDM or Particle Dynamics Method for simulation of clastic sediment motion has been used to study the motion of clastic sediment at the level of the individual particle. This technique can be used to assign properties to sediment beds like grain size and grain size distribution, grain shape, and so forth, and then to study the response of the sy...

Stratigraphic patterns preserved under translating surface undulations or ripples in a depositional eolian environment are computed on a grain by grain basis using physically based cellular automata models. The spontaneous appearance, growth, and motion of the simulated ripples correspond in many respects to the behavior of natural ripples. The sim...

Continuum theories of highly agitated granular flows have recently been developed based on ideas from the kinetic theory of gases, with the fluctuation velocity of the grains corresponding to the temperature of the gas. Most often the boundary conditions for a granular system at a wall have been taken to be the same as the boundary conditions for a...

A model of eolian sediment transport has been constructed, a special case of which is that corresponding to sand-sized mineral grains subjected to moderate winds: saltation. The model consists of four compartments corresponding to (1) aerodynamic entrainment, (2) grain trajectories, (3) grain-bed impacts, and (4) momentum extraction from the wind....

First Page of the Article

A model of eolian sediment transport has been constructed, a special case of which is that corresponding to sand-sized mineral grains subjected to moderate winds: saltation. The model consists of four compartments corresponding to aerodynamic entrainment, grain trajectories, grain-bed impacts, and momentum extraction from the wind. Each sub-model e...

Numerical simulation of the eolian saltation process has produced tightly constrained probability distributions of hop lengths, impact angles, and speeds, as well as the total numbers of grains in saltation for any given combination of grain size, density, and wind speed. These distributions allow modeling of two processes important to the developm...

A summary of progress which has been made on the computer simulated and modeling of wind blown sand transport is included. Keywords: Abstracts; Sediments; Suspended particles; Mass fluxes; Sand; Suspensions; Saltation; Wind; Fluid dynamics.

A technique for simulating the motion of granular materials using the Caltech Hypercube is described. We demonstrate that grain dynamics simulations run efficiently on the Hypercube and therefore that they offer an opportunity for greatly expanding the use of parallel simulations in studying granular materials. Several examples, which illustrate ho...

A technique for simulating the motion of granular materials using the Caltech Hypercube is described. We demonstrate that grain dynamics simulations run efficiently on the Hypercube and therefore that they offer an opportunity for greatly expanding the use of parallel simulations in studying granular materials. Several examples, which illustrate ho...

Saltation is important in the transport of sand-sized granular material by wind and in the ejection of dust from the bed both on Earth and on Mars. The evolution of the saltating population and all its characteristic profiles is calculated from inception by pure aerodynamic entrainment through to steady state. Results of numerical simulations of si...

Coupled equations of motion for steady state saltation over an infinite plane are derived and solved for a simplified model of the grain‐surface impact process. Experimentally observed features of the wind velocity profile in saltation are qualitatively reproduced, including a diminution of the sub‐saltation layer mean wind speed, as the friction s...

We report the results of impact experiments in which high velocity steel spheres (BBs) were directed against a loose bed of similar particles. The purpose of these experiments is to shed some light on the collision processes which occur when saltating sand grains driven by the wind strike the bed. The scattered particles fall into two categories: a...

A two-dimensional system of inelastic frictional disks all of equal diameter save one was studied by computer simulation. A single large disk was placed on the bottom of a container and covered by 30 smaller disks. When the container was agitated to induce a shear motion in the disk assembly, the large particle showed a tendency to rise toward the...

We give a physical and heuristic discussion of the kinetic model of granular fluids, wherein the grain plays the role of a molecule. A consideration of the details of grain‐grain and grain‐wall interactions leads naturally to the equations of motion and to suitable boundary conditions. Examples from a Couette flow geometry are used to support the a...

The dynamics of granular materials has proved difficult to model, primarily because of the complications arising from inelastic losses, friction, packing, and the effect of many grains being in contact simultaneously. The kinetic model of granular systems is similar to the kinetic theory of gases, except that collisional energy losses are always pr...

Proceeding from the observation that planetary satellites are important sources of mass for planetary magnetospheres, it is noted that meteoroid impact vaporization may compete with charged particle sputtering as a supply mechanism. After considering meteoroid-driven vapor sources in the Jovian and Kronian systems, it is concluded that while the la...

A self-consistent kinetic grain flow model proposed earlier has been applied in detail to the description of rapid flow in a verticad channel. The equations of motion reduce to an ordinary differential equation for the fluctuation velocity , which is solved numerically. Boundary conditions on are derived which incorporate the nature of grain-wall c...

The sputtering of Cu atoms from liquid targets by normally incident 5 keV Ar+ ions was simulated using the multiple interaction molecular dynamics technique. Yields, energy distributions, and angular distributions of sputtered atoms were obtained at several temperatures slightly above and below the experimental melting point of copper. In all cases...

Assuming that the profiles of eolian sand ripples remain constant over a short distance, it is possible to measure their shapes by casting a shadow perpendicular to the ripple crests. We describe a method whereby this can be done accurately and easily. Tests of the method demonstrate that accuracies on the order of one sand-grain diameter can be ac...

The multiple interaction, molecular dynamics code SPUT1 has been used to simulate the effects of isotopic mass differences on atoms sputtered from single crystal Cu targets by normally incident Ar ions. Calculations were carried out for 1 keV and 5 keV ions incident on natural Cu targets (69.1% 63Cu, 30.9% 65Cu). and for 5 keV ions incident on pseu...

The energy and angular distributions of copper atoms ejected by 5 keV incident Ar ions have been simulated using the multiple interaction molecular dynamics technique. Calculations carried out with two independently written computer codes yielded essentially identical results. As in previous simulation studies of low to medium energy sputtering, vi...

Material ejected from the surfaces of satellites in the outer solar system plays an important role in the magnetospheres of the outer planets, and may dominate the mass loading, as in the vicinity of the Jovian satellite Io. At least four potential ejection mechanisms can be identified - intrinsic geologic activity, thermal sublimation, sputtering,...

Boundary conditions are developed for rapid granular flows in which the rheology is dominated by grain–grain collisions. These conditions are $\overline{v}_0 = {\rm const}\,{\rm d}\overline{v}_0/{\rm d}y$ and u0 = const du0/dy, where $\overline{v}$ and u are the thermal (fluctuation) and flow velocities respectively, and the subscript indicates tha...

The E ring associated with the Kronian moon Enceladus has a lifetime of only a few thousand years against sputteringly by slow corotating O ions. The existence of the ring implies the necessity for a continuous supply of matter. Possible particle source mechanisms on Enceladus include meteoroidal impact ejection and geysering. Estimates of ejection...