Thematic Articles

The Odds and Evens of Mercury Isotopes: Applications of Mass-Dependent and Mass-Independent Isotope Fractionation

Mercury (Hg) is a redox-active trace metal that is viewed internationally as a priority pollutant. Research into Hg stable isotope biogeochemistry is rapidly providing new insight into the behavior of Hg. With the recent discovery that Hg can exhibit both mass-dependent (MDF) and mass-independent fractionation (MIF) (range of >6‰ for both), Hg isotopes are providing a valuable new tool for tracing this important toxin through the environment. MDF alone, which occurs during redox transformations, biological cycling, and volatilization of Hg, can be exploited to increase understanding of the processes that control Hg distribution and bioaccumulation. The addition of MIF signatures greatly increases the usefulness of Hg isotopes because MIF provides a unique fingerprint of specific chemical pathways, such as photochemical reduction.

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Metal Stable Isotopes in Low-Temperature Systems: A Primer

Recent advances in mass spectrometry have allowed isotope scientists to precisely determine stable isotope variations in the metallic elements. Biologically influenced and truly inorganic isotope fractionation processes have been demonstrated over the mass range of metals. This Elements issue provides an overview of the application of metal stable isotopes to low-temperature systems, which extend across the borders of several science disciplines: geology, hydrology, biology, environmental science, and biomedicine. Information on instrumentation, fractionation processes, data-reporting terminology, and reference materials presented here will help the reader to better understand this rapidly evolving field.

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Visual Communication: Do You See What I See?

Visual displays of data, images of subatomic to planetary-scale features, and animations of geological processes are widely used to enrich our disciplines. However, their communicative power may be dramatically different to a student and to an expert because of the need for prior knowledge and inference when interpreting visuals. To “see” equivalent visual information, the non-expert must learn the visual language of the expert. Teaching visual literacy is important to instruction at all levels and is as fundamental to a discipline as its vocabulary. The underlying foundations of visual literacy and the recognition of what one “sees” and interprets in a visual depiction are critical for enhancing student learning and for effective communication in our visually rich discipline.

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Using Alignment and Reflection to Improve Student Learning

Greater participation, and the associated increase in student diversity, has changed university education worldwide. The old ways of teaching a small number of well-qualified committed students do not work as well with large classes and more diverse student needs. This essay documents one approach to this challenge. It involves understanding student needs and preferences better, developing a range of ways to deliver learning and assess the results, and finally reflecting on the outcomes. The annual process of reflection allows changes that improve alignment of course aims with their delivery and assessment, and results in improved student learning and perception of the subject.

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Teaching for Deeper Understanding and Lifelong Learning

A growing body of research confirms that active approaches to learning offer many advantages over traditional instructional methods, including improved retention of information, conceptual understanding, and problem-solving skills. Content coverage in active-learning courses can be facilitated through careful selection and design of activities that guide student learning. Importantly, activities should engage groups of students in cooperative questioning, problem solving, analytical reasoning, and critical thinking. Focused instruction and reflection on thinking and learning help students develop as intentional learners.

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What Should Our Students Learn?

Traditionally, college science teachers have focused on delivering content to students. The assumption was that students would learn the information and could recall and use it later. Current research on learning, however, tells us that such an approach to teaching, by itself, is not the best way to promote learning. Learning is not a process that simply involves knowledge transfer. Instead, it is a physiological process that involves changes in the brain. Good teaching, therefore, should focus on helping students develop their cognitive skills, while simultaneously helping them become better learners. Students will learn specific ideas and facts in our classes, but the information learned is of much less importance than the learning and thinking skills acquired. Our overall goal should be to help students become lifelong learners, successful as citizens and professionals. Assessment and self-reflection are keys. Students must learn to reflect on, and assess, their own learning. Instructors must also constantly assess their own efforts to promote student learning.

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Improving Instruction in Mineralogy, Petrology, and Geochemistry— Lessons from Research on Learning

Effective instruction can enhance our ability to retain students in the geoscience major and to raise their level of expertise in mineralogy, petrology, and geochemistry (MPG). Research on learning and education provides a framework for designing learning experiences in our classes. As a community we are well positioned to consider the goals of MPG instruction and to evaluate the materials and methods we currently use in our teaching. This will enhance the ability of faculty members to design and implement courses that meet the needs of their department and capitalize on their strengths as teachers.

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New Directions at the Intersection of Research about Earth and Research on Learning

New advances in cognitive psychology and learning science provide insights into how people construct knowledge, with important implications for how we learn from, and teach about, the Earth. Research on learning has demonstrated that effective instructional practices require students to construct their own knowledge bases (i.e. a shift in emphasis from teaching to learning), address diverse student learning styles, employ a variety of active-learning strategies, and encourage inquiry and discovery. These emerging principles provide a context for us to reflect collectively on what and how we teach in our mineralogy, petrology, and geochemistry courses. If we are to meet the challenges of the 21st century, our new instructional goal should be to develop students who are lifelong learners and who use the knowledge base, technical skills, and cognitive strategies that are used by “master” geoscientists. As a result, we will help sustain the long-term health and relevance of the mineralogy, petrology, and geochemistry community

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Gold and Nanotechnology

The properties of gold change dramatically at the nanoscale. Gold nanoparticles and nanoporous gold have remarkable optical and catalytic properties, which are being investigated for applications in biomedicine and manufacturing. Using a variety of synthetic methods, the shape, size and properties of these materials can be optimized, making them a powerful platform for the development of new contrast agents for optical imaging of biological tissues, photothermal destruction of tumours and catalysis of various reactions.

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The Biogeochemistry of Gold

The biosphere catalyzes a variety of biogeochemical reactions that can transform gold. Microbial weathering contributes to the mobilization of gold by releasing elemental gold trapped within minerals and by solubilizing gold via oxidation-promoting complexation. Subsequent microbial destabilization of gold complexes coupled with bioprecipitation and biomineralization can immobilize gold, completing the cycle. Secondary gold can occur as colloidal particles, crystalline gold and bacteriomorphic structures, the latter being a controversial form of ‘biogenic’ gold.

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December 2025 --The Variscan Orogeny in Europe – Understanding Supercontinent Formation

The Variscan orogen formed between 380 and 300 million years ago through several accretionary and collisional cycles, culminating with the construction of the Pangea supercontinent. This process occurred via sequential opening and closure of oceanic basins, synchronous detachment of Gondwana derived continental ribbons, and their outboard amalgamation onto the Laurussia margin. The Variscan orogen is rather unique compared with other orogenic belts on Earth: its overthickened and dominantly magmatic crust in the central belt, surprisingly minor mantle involvement in the magmatic and geodynamic processes, coherent and pulsed magmatism along the collision suture, and its complex accretionary history. Because its final product, Pangea, is the youngest and best-understood supercontinent on Earth, the Variscan orogeny offers clues for understanding the mechanisms of supercontinent formation.