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"Geochemical cycles."
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Investigating the rock cycle
Igneous rocks, sedimentary rocks, and metamorphic rocks make up the three main types of rocks and are constantly being created, destroyed, and created again? Colorful illustrations show how the rock cycle works.
Book
Review article: Global monitoring of snow water equivalent using high-frequency radar remote sensing
Seasonal snow cover is the largest single component of the cryosphere in areal extent, covering an average of 46 × 106 km2 of Earth's surface (31 % of the land area) each year, and is thus an important expression and driver of the Earth's climate. In recent years, Northern Hemisphere spring snow cover has been declining at about the same rate (∼ −13 % per decade) as Arctic summer sea ice. More than one-sixth of the world's population relies on seasonal snowpack and glaciers for a water supply that is likely to decrease this century. Snow is also a critical component of Earth's cold regions' ecosystems, in which wildlife, vegetation, and snow are strongly interconnected. Snow water equivalent (SWE) describes the quantity of water stored as snow on the land surface and is of fundamental importance to water, energy, and geochemical cycles. Quality global SWE estimates are lacking. Given the vast seasonal extent combined with the spatially variable nature of snow distribution at regional and local scales, surface observations are not able to provide sufficient SWE information. Satellite observations presently cannot provide SWE information at the spatial and temporal resolutions required to address science and high-socio-economic-value applications such as water resource management and streamflow forecasting. In this paper, we review the potential contribution of X- and Ku-band synthetic aperture radar (SAR) for global monitoring of SWE. SAR can image the surface during both day and night regardless of cloud cover, allowing high-frequency revisit at high spatial resolution as demonstrated by missions such as Sentinel-1. The physical basis for estimating SWE from X- and Ku-band radar measurements at local scales is volume scattering by millimeter-scale snow grains. Inference of global snow properties from SAR requires an interdisciplinary approach based on field observations of snow microstructure, physical snow modeling, electromagnetic theory, and retrieval strategies over a range of scales. New field measurement capabilities have enabled significant advances in understanding snow microstructure such as grain size, density, and layering. We describe radar interactions with snow-covered landscapes, the small but rapidly growing number of field datasets used to evaluate retrieval algorithms, the characterization of snowpack properties using radar measurements, and the refinement of retrieval algorithms via synergy with other microwave remote sensing approaches. This review serves to inform the broader snow research, monitoring, and application communities on progress made in recent decades and sets the stage for a new era in SWE remote sensing from SAR measurements.
Journal Article
The rock cycle
\"Within the rock cycle, there are so many other processes! Weather, erosion, and the creation of metamorphic, igneous, and sedimentary rock are all part of the greater process scientists call the rock cycle. In this colorful and engaging volume, readers read about each process in accessible language and then review it in an easy-to-follow flowchart. Full of Earth science content that supports classroom learning, the main content guides readers through important subject areas including what rock is made of, how minerals are used, and metal mining. Full-color photographs correlate to and complement each chapter.\"--Amazon.
Book
Microbial Biodeterioration of Cultural Heritage
Geochemical cycles result in the chemical, physical, and mineralogical modification of rocks, eventually leading to formation of soil. However, when the stones and rocks are a part of historic buildings and monuments, the effects are deleterious. In addition, microorganisms also colonize these monuments over a period of time, resulting in formation of biofilms; their metabolites lead to physical weakening and discoloration of stone eventually. This process, known as biodeterioration, leads to a significant loss of cultural heritage. For formulating effective conservation strategies to prevent biodeterioration and restore monuments, it is important to know which microorganisms are colonizing the substrate and the different energy sources they consume to sustain themselves. With this view in scope, this review focuses on studies that have attempted to understand the process of biodeterioration, the mechanisms by which they colonize and affect the monuments, the techniques used for assessment of biodeterioration, and conservation strategies that aim to preserve the original integrity of the monuments. This review also includes the “omics” technologies that have started playing a large role in elucidating the nature of microorganisms, and how they can play a role in hastening the formulation of effective conservation strategies.
Journal Article
The rock cycle
\"Get ready to get your hands dirty with The Rock Cycle. With its reader-friendly and interactive approach, this title covers key curriculum Earth science topics in an engaging way. This title explores the natural processes, how geologists study the rock cycle, and how the rock cycle relates to the reader's daily life\"-- Publisher's description.
Book
Early Archaean onset of volatile cycling at subduction zones
The subduction of pelagic sediments and altered oceanic crust modulates the global cycle of volatile elements. Sulfate and carbonate fluids released when one plate descends beneath another modify the redox state of the mantle, and generate the return of water and reactive gases to the atmosphere and hydrosphere via arc volcanism, affecting planetary habitability over geologic timescales. However, the timing of the onset of subduction remains uncertain, hindering our understanding of how deep geochemical cycles operated on the early Earth. Here we measure sulfur and neodymium isotope data on Eoarchaean mantle-derived rocks of the Innuksuac Complex in northern Québec, Canada, with petrological characteristics of arc magmas. These rocks exhibit anomalous sulfur isotopic compositions originally produced by photochemical reactions in the atmosphere more than 3.8 Gyr ago. Combined sulfur and neodymium isotope data suggest that these signatures were transferred to the Innuksuac mantle through devolatilization and partial melting of terrigenous sediments derived from a Hadean (4.3–4.4 Gyr ago) continental source, providing a record of an early continental margin subduction environment. This result pushes back direct evidence of a subduction-driven volatile cycle to the onset of the terrestrial rock record, approximately 1 Gyr earlier than previously inferred from diamond inclusions.
Combined sulfur and neodymium isotopes suggest that volatile cycling at subduction zones began 3.8 Gyr ago or earlier, according to a study of Eoarchaean mantle-derived rocks with arc-lava characteristics.
Journal Article
A look at minerals
\"Describes minerals, how they are formed and how they are used\"-- Provided by publisher.
BOOK
Abrupt episode of mid-Cretaceous ocean acidification triggered by massive volcanism
Large-igneous-province volcanic activity during the mid-Cretaceous triggered a global-scale episode of reduced marine oxygen levels known as Oceanic Anoxic Event 2 approximately 94.5 million years ago. It has been hypothesized that this geologically rapid degassing of volcanic carbon dioxide altered seawater carbonate chemistry, affecting marine ecosystems, geochemical cycles and sedimentation. Here we report on two sites drilled by the International Ocean Discovery Program offshore of southwest Australia that exhibit clear evidence for suppressed pelagic carbonate sedimentation in the form of a stratigraphic interval barren of carbonate minerals, recording ocean acidification during the event. We then use the osmium isotopic composition of bulk sediments to directly link this protracted ~600 kyr shoaling of the marine calcite compensation depth to the onset of volcanic activity. This decrease in marine pH was prolonged by biogeochemical feedbacks in highly productive regions where elevated heterotrophic respiration added carbon dioxide to the water column. A compilation of mid-Cretaceous marine stratigraphic records reveals a contemporaneous decrease of sedimentary carbonate content at continental slope sites globally. Thus, we contend that changes in marine carbonate chemistry are a primary ecological stress and important consequence of rapid emission of carbon dioxide during many large-igneous-province eruptions in the geologic past.Volcanic activity led to ocean acidification at the onset of Oceanic Anoxic Event 2, which then persisted for 600,000 years due to biogeochemical feedbacks, according to marine osmium isotope and carbonate sedimentation records offshore from southwest Australia.
Journal Article
A look at metamorphic rocks
\"Describes metamorphic rocks, how they are formed, how they are used, and their role in the rock cycle\"-- Provided by publisher.
Book
Characteristics, origins, and significance of pyrites in deep-water shales
As important metal sulfides in the geochemical cycle of sulfur, the characteristics and formation processes of pyrites can provide useful clues regarding their environment. Based on previous findings, shale pyrites were divided into three major classes (euhedral pyrites, framboidal pyrites (framboids) and metasomatic pyrites) and six sub-classes in this study. At the microscopic scale, each type of pyrite is associated with a different formation process. Framboids are formed by burst nucleation in environments with a homogeneous distribution of nutrients while euhedral pyrites are usually formed on pre-existing sites (such as =FeS on the minerals surface) in the heterogeneous system. Metasomatic pyrites formed by the replacement of other ions in accountable material by iron ions and hydrogen sulfide ions in hydrothermal events. The morphology and isotope value of pyrite provide information to track the origins of their nutrient and characteristics of sulfur and iron pools. In addition, the trace element content of pyrite can serve as a proxy for paleo-ocean trace element abundance, indicating changes in atmospheric oxygen content. Additionally, pyrite can also serves as an indicator of shale gas reservoirs.
Journal Article