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I n the essay series “Places that Reveal the Geological Mind,” we are going to explore what goes on in a mind at the cutting edge of disciplinary practice and when first learning geology. We have selected a series of places on Earth that reveal both geological processes and the mental processes that extract knowledge from rocks. Thomas (Tim) Shipley, a professor of cognitive science, has now been working with geologists and geoscience educators for over two decades. Funding from the NSF-sponsored Spatial Intelligence and Learning Center catalyzed leaving his familiar cognitive science community behind to try to understand how another scientific community thinks. Basil Tikoff, a professor of geology, has been a willing collaborator in the effort to link cognitive science and geology. The appeal, originally, was to understand spatial learning in a field that requires high levels of spatial thinking. It became apparent that understanding how one knows the natural world revealed aspects of spatial thinking that were not recognized by the cognitive science community. This series is the product of their ongoing collaboration. [ABSTRACT FROM AUTHOR]

* Sketching is a valuable but underutilized tool for science education. Sketch worksheets were developed to help change this, by using artificial intelligence technology to give students immediate feedback and [...]

The field of geology is poised to make a fundamental transition in the quality, character, and types of science that are possible for practitioners. Geologists are developing data systems--consistent with their workflow--to digitally collect, store, and share data. Separately, geologists and cognitive scientists have been working together to develop tools that can characterize the level of uncertainty of both data and models. The transformational change comes from the simultaneous combination of these two approaches: digital data systems designed to capture and convey scientific uncertainty. This approach promotes better data collection practice, improves reproducibility, and increases trust in community-based digital data. We applied these methods--attending to uncertainty and its incorporation into digital repositories--to the Sage Hen Flat pluton in eastern California, USA, where two published maps provide different interpretations. Incorporating uncertainty into our workflow, from field data collection to publication, allows us to move beyond binary choices (e.g., is this data/model right or wrong?) to a more nuanced view (e.g., what is my level of uncertainty about the data/model?) that is shareable with the larger community. [ABSTRACT FROM AUTHOR]

AbstractSpatial skills are embedded in all aspects of the geosciences. The teaching and learning of spatial skills has been a challenging, but vital, endeavor. To support student learning of spatial skills in undergraduate courses, we designed scaffolds for spatially dependent content in a mid-level geoscience course using playdough to allow students to model and manipulate geologic structures and processes. Using a semester-long geology course as a case study, we explore the ways in which students reported playdough supported their learning of geoscience content during the course. Students found the playdough most helpful for visualizing geologic structures, such as faults and domes, which students were then able to encode into their long-term memories, or “mental libraries,” for application to new contexts on assessments later. The playdough was more helpful at the start of the course when students were grappling with introductory course content and skills. Later in the course, the need for the playdough as a scaffold faded, as intended. Most students eventually sought new scaffolds, such as three-dimensional block models, which illustrate more complex and sophisticated structures and processes. Therefore, we see playdough as a useful scaffold for students in the early stages of spatial and geologic skill development as it aids students in developing both sets of skills. It is easy to utilize, inexpensive, portable, widely available, and familiar to most students.

The physical process of rhyolite segregation from crystal mushes remains elusive as microstructural evidence of conventional segregation mechanisms is not available. This study provides direct fabric evidence for deformation‐assisted segregation of eruptible rhyolite in the Chilean Andean arc. The shallow (<7 km), 6.4–6.2 Ma Huemul pluton comprises domains of quartz monzonite, granite, and high‐silica granite. Compositional modeling shows that rhyolitic melt (high‐silica granite) was extracted from a granitic parent, leaving behind silicic cumulates (quartz monzonite). To understand mechanisms of rhyolite segregation, we investigate magmatic fabrics in the pluton. Anisotropy of Magnetic Susceptibility analyses reveal oblate magnetic fabrics and NNW‐striking, subvertical magnetic foliations throughout Huemul. Within the high‐silica granite, magnetic lineations are subvertical and parallel to elongate miarolitic cavities. Magnetic lineations in the quartz monzoniteplunge moderately to the NNW, away from the high‐silica granite. In the quartz monzonite, the Shape‐Preferred Orientation of early feldspars is parallel to the magnetic lineation and developed while suspended in melt. Estimations of early feldspar clustering and crystallinity yield ~38% of interstitial volume loss in the quartz monzoniteand no volume loss in the granite. These fabric data suggest ENE tectonic shortening coeval with rhyolite extraction. We explain these observations with a model of tectonic filter pressing in which shortening is accommodated by interstitial melt flow at slow (10−5km3/yr) rates, segregating moderate volumes of rhyolite in Myr time scales. These interactions link plutonism, tectonic deformation, and upward mobility of eruptible rhyolite in tectonically active margins. Granitic fabrics in a silicic pluton show rhyolite segregation, accumulation, and extraction coeval with tectonic shorteningWe interpret that a portion of tectonic shortening is accommodated by displaced interstitial melt, that is, tectonic filter pressingTectonic filter pressing may be the key connecting segregation of rhyolite in volcanic and tectonic time scales in active arcs

ABSTRACTThis manuscript addresses the potential role of geoscience education research in understanding geoscience expert practice. We note the similarity between the perception–action framework of Ulric Neisser (Neisser, 1976) and the observation–prediction framework used by geoscience practitioners. The consilience between these two approaches is that learning takes place when links are formed between predictions and observations and that this linkage is formed through conceptual models. Use of conceptual models facilitates learning at all levels; hence, there is little difference between learning in expert practice and student learning at all levels. The field of geoscience education is uniquely poised to enhance geoscience practice through investigation of expert learning, both in traditional field research and when experts adopt new tools and techniques. The consilience of expert practice, student learning, and cognitive science outcomes provides a rich opportunity to enhance both the intellectual merit of research and the direct and indirect broader impacts.

ABSTRACTSpatial visualization is an essential prerequisite for understanding geological features at all scales, such as the atomic structures of minerals, the geometry of a complex fault system, or the architecture of sedimentary deposits. Undergraduate geoscience majors bring a range of spatial skill levels to upper-level courses. Fortunately, spatial thinking improves with practice, and students benefit from intentional training. Several promising teaching strategies have emerged from recent cognitive science research into spatial thinking: gesturing, predictive sketching, and comparison, including analogy and alignment. Geoscience educators have traditionally incorporated many of these tools in their teaching, though not always consciously, intentionally, and in the most effective ways. Our research team, composed of geoscientists and cognitive psychologists, has collaborated to develop curricular materials for mineralogy, structural geology, and sedimentology and stratigraphy courses that incorporate these strategies intentionally and purposefully, supporting student understanding of the spatially challenging concepts and skills in these courses. Collectively, these two dozen learning activities comprise the Spatial Thinking Workbook (http://serc.carleton.edu/spatialworkbook/index.html). Pre- to posttest gains on a suite of assessment instruments, as well as embedded assessments, show that these curricular materials boost students' spatial thinking skills and strengthen their ability to solve geological problems with a spatial component.

Tuolumne Meadows, in Yosemite National Park (USA), is a large sub-alpine meadow in the Sierra Nevada Mountains. Immediately adjacent to Tuolumne Meadows--and underlain by the same bedrock lithology (Cathedral Peak Granodiorite)--are vertical rock faces that provide exceptional opportunities to climbers. While the presence of a broad meadow suggests bedrock erodibility, the vertical rock walls indicate bedrock durability. We propose that the Tuolumne Meadows's landscape is the result of variable glacial erosion due to the presence or absence of preexisting bedrock fractures. The meadows and valleys formed because of concentrated tabular fracture clusters--a distinctive and locally pervasive type of fracturing--that were particularly susceptible to glacial erosion. In contrast, the vertical rock walls consist of sparsely fractured bedrock that was originally bounded by zones of pervasive tabular fracture clusters. Glacial erosion preferentially removed the highly fractured rock, forming prominent ridges in the upland surrounding Tuolumne Meadows. The orientation and spacing of the tabular fracture clusters, relative to ice flow, has exerted a fundamental control on the geomorphology of the area. The erosional variability exhibited by a single lithology indicates that the degree of fracturing can be more important than the host lithology in controlling landscape evolution. [ABSTRACT FROM AUTHOR]

The Paleoarchean Mt Edgar dome in the East Pilbara Terrane has long been studied as an archetypal dome within Archean dome‐and‐keel terranes, but the history of its formation is debated. Kinematic data presented in this study provide new insights into the late‐stage development of the Mt Edgar dome and East Pilbara Terrane. Quartz crystallographic preferred orientation (CPO), optical microstructures, and field structures all indicate that the granite‐greenstone contact of the Mt Edgar dome experienced reverse (greenstone‐up, dome‐down) sense of shear after the formation of the dominant schistosity. This reverse sense of shear is observed at localities along the entire extent of the sheared margin that rings most of the Mt Edgar dome, but is best documented along the southwest margin in the Warrawoona Greenstone Belt. Additionally, quartz CPO data from a dome triple junction outside of the sheared margin dominantly indicate a constrictional strain geometry, consistent with the previous interpretation that this area represents a zone of vertical foundering in a buoyancy‐instability driven system. However, buoyancy‐instability models do not necessarily predict the occurrence of greenstone‐up sense of shear preserved in solid‐state fabrics along the dome margin. Several geologic explanations are considered, including dome expansion or post‐doming deformation. The data are most consistent with explanations that directly relate to dome formation, especially when considered in tandem with recently published structural data from within the Mt Edgar dome. These kinematic data suggest that late dome development occurred in a near‐static crustal environment rather than an extensional or contractional setting. The granite‐greenstone interface at the margin of the granitic Mt Edgar dome is characterized by a late‐stage greenstone‐up sense of shearStrain geometry within the Warrawoona Greenstone Belt varies from constrictional to flatteningThe East Pilbara Terrane domes likely formed as diapiric structures in a near‐static crust The granite‐greenstone interface at the margin of the granitic Mt Edgar dome is characterized by a late‐stage greenstone‐up sense of shear Strain geometry within the Warrawoona Greenstone Belt varies from constrictional to flattening The East Pilbara Terrane domes likely formed as diapiric structures in a near‐static crust

ABSTRACTSpatial thinking skills are critical to success in many subdisciplines of the geosciences. We tested students' spatial skills in geoscience courses at three institutions (a public research university, a comprehensive university, and a liberal arts college, all in the midwest) over a two-year period. We administered standard psychometric tests of spatial skills to students in introductory geology, mineralogy, sedimentology and stratigraphy, hydrogeology, structural geology, and tectonics courses. In addition, in some courses we administered a related spatial skills test with geoscience content. In both introductory and upper level undergraduate geology courses, students' skills vary enormously as measured by several spatial thinking instruments. Additionally, students' spatial skills generally improve only slightly during one academic term, in both introductory and advanced geoscience classes. More unexpectedly, while there was a tendency for high-performing students to be adept at multiple spatial skills, many individual students showed strong performance on tests of one spatial skill (e.g., rotation) but not on others (e.g., penetrative thinking). This result supports the contention that spatial problem solving requires a suite of spatial skills, and no single test is a good predictor of “spatial thinking.”

Recent structural and geodetic data define the Guatemala City graben region as the continental triple junction between the North American plate, Caribbean plate, and the Central American Forearc sliver. We present minor fault analysis, geochronological and geochemical analyses, and newly updated GPS velocities in western Guatemala, west of the Guatemala City graben, to characterize the magnitude and timing of extensional deformation in this poorly understood area. Elongations estimated from fault data are parallel (∼east‐west) and perpendicular to the Polochic‐Motagua fault system to the north, similar to geodetically measured active deformation observed east of the Guatemala City graben. Four new 40Ar/39Ar dates and correlation of tephra deposits suggest that faulting was active during the Pliocene, but ceased eastward toward the Guatemala City graben over time. From west to east, fault cessation occurred before the deposition of the Los Chocoyos ash (75 ka) and E tephra (51 ka). Faulting just west of the Guatemala City graben appears to be active, where a major fault cuts the most recent Amatitlán tephras. Based on this data, we propose a time‐progressive strain model for deformation related to North America‐Caribbean plate interactions, whereby distributed elongation of the westernmost Caribbean plate occurred during the Pliocene but localized mostly within the Guatemala City graben and nearby faults during the Pleistocene. Our model supports that: (a) The Guatemala City graben is effectively the western limit of the Caribbean plate; and (b) Western Guatemala, which was the trailing edge of the Caribbean plate, has been transferred to the forearc region. Distributed deformation once extended across Guatemala and into Honduras and has localized into the Guatemala City graben region over timeThe Guatemala City graben region is the current North America, Central American Forearc, and Caribbean plate triple junctionFaulting in western Guatemala, representing internal deformation of the Caribbean plate, ceased in an eastward direction over the past ∼4 Ma Distributed deformation once extended across Guatemala and into Honduras and has localized into the Guatemala City graben region over time The Guatemala City graben region is the current North America, Central American Forearc, and Caribbean plate triple junction Faulting in western Guatemala, representing internal deformation of the Caribbean plate, ceased in an eastward direction over the past ∼4 Ma

Geoscience instructors and textbooks rely on analogy for teaching students a wide range of content, from the most basic concepts to highly complicated systems. The goal of this paper is to connect educational and cognitive science research on analogical thinking with issues of geoscience instruction. Analogies convey that the same basic relationships hold in two different examples. In cognitive science, analogical comparisonis understood as the process by which a person processes an analogy. We use a cognitive framework for analogy to discuss what makes an effective analogy, the various forms of analogical comparison used in instruction, and the ways that analogical thinking can be supported. Challenges and limitations in using analogy are also discussed, along with suggestions about how these limitations can be addressed to better guide instruction. We end with recommendations about the use of analogy for instruction, and for future research on analogy as it relates to geoscience learning.

The rhyolite‐producing Laguna del Maule volcanic field (LdMVF), Chile, has had numerous post‐glacial eruptions that produced large explosions and voluminous lava flows. During the Holocene ∼60 m of surface uplift is recorded by paleo‐shorelines of the fresh‐water Laguna del Maule, with an inflation source near the Barrancas volcanic complex. Rhyolites from the Barrancas complex erupted over ∼14 ka including some of the youngest (1.4 ± 0.6 ka) lava flows in the field. New gravity data collected on the Barrancas complex reveals a residual gravity low (−6 mGal, “Barrancas anomaly”) that is distinct from the pronounced gravity low (−19 mGal; “Lake anomaly”) associated with present‐day ground uplift to the northwest. Three‐dimensional inversion of the Barrancas anomaly indicates the presence of a magma body with a maximum density contrast with the host rock of −250 kg/m3centered at a depth of ∼3 km below surface. Nearby Miocene high‐silica granites represent frozen remnants of highly evolved rhyolitic magma. Comparison of the densities measured from samples of these plutons with the geophysical model densities, and integration of thermodynamic modeling of silicic melt evolution, provide constraints on our interpretation. We propose a magma body, containing <30% melt phase and low volatile content, exists beneath Barrancas. The Barrancas and Lake gravity lows represent magma in different physical states, associated with past and present‐day storage beneath LdMVF. The gravity model mirrors geochemical observations which independently indicate that at least two distinct rhyolites were generated and stored as discrete magma bodies within the broader LdMVF. The Laguna del Maule volcanic field (LdMVF) in Chile, has a long history of eruptions that produced large explosions and voluminous lava flows. Lava emitted during these eruptions comes from shallow sources of partially molten rock (magma) located a few kilometers below the surface. Magma pushing from below and into these shallow regions has caused the ground around the lake to rise over the last 10,000 years. To understand the causes of deformation and assess the likelihood of future eruptions, it is essential to know the location and present‐day state of magma within Earth's crust. Magma is typically less dense than the surrounding rock and these density variations cause small changes in the local gravity field, detectable with geophysical instruments. We collected a new set of gravity measurements at the Barrancas volcanic complex to determine if magma is present beneath the volcano that last erupted about 2000 years ago. Our data reveal a shallow magma body at depth beneath the Barrancas complex. This new magma body is separate from another magma body located in a different part of the LdMVF, which has important implications for the assessment of future volcanic hazards in the region. At least two separate magma storage regions in different physical states exist beneath the Laguna del Maule volcanic fieldA −6 mGal gravity anomaly below the Barrancas complex is close to a postulated inflation source which produced ∼62 m of Holocene upliftComparing model densities to nearby plutons and seismic models indicates Barrancas magma is above solidus with a small melt proportion At least two separate magma storage regions in different physical states exist beneath the Laguna del Maule volcanic field A −6 mGal gravity anomaly below the Barrancas complex is close to a postulated inflation source which produced ∼62 m of Holocene uplift Comparing model densities to nearby plutons and seismic models indicates Barrancas magma is above solidus with a small melt proportion

Ductile shear zones and associated stretching lineations are generally considered to be the result of two-dimensional, simple shear deformations, with stretching lineations interpreted to rotate into parallelism with the direction of tectonic transport with increasing deformation. However, stretching lineations perpendicular to the inferred tectonic transport direction are displayed by some shear zones. Field studies in the Sierra Nevada batholith have revealed a single shear zone (the Rosy Finch-Gem Lake shear zone) that contains both steeply-plunging stretching lineations in older metamorphosed sedimentary and granitic rocks, and shallowly-plunging stretching lineations in syntectonic granitoids. Dextral sense-of-shear indicators are found in all these units and deformation occurred simultaneously along the length of the shear zone.

Any simultaneous combination of finite simple shear and finite pure shear is a linear transformation which can be expressed as a single transformation matrix. For two dimensions, the matrix is upper triangular with an off-diagonal term, Γ, called the effective shear strain. Γ is a simple function of the pure and simple shear components. For three dimensions, a simultaneous combination of thrusting in the xdirection, thrusting in the ydirection, and a wrench in the xdirection, in addition to 3 orthogonal components of coaxial strain, can also be represented by a 3 × 3, upper triangular matrix. Here, three off-diagonal terms ( Γxy, Γx, y, and Γy, z) occur. Γxyis a simple function of the horizontal coaxial strain values and thrusting in the xdirection, Γyzdepends on the coaxial strain components in the yand zdirections and the thrusting in the ydirection, while Γxzis related to all six strain components. The matrix also allows for volume change, either homogeneously or preferentially in a single direction. A method of decomposing the deformation matrix into a series of incremental deformation matrices, where each incremental deformation records the same kinematic vorticity number as the finite deformation is shown. The orientation and magnitude of the finite-strain ellipsoid (ellipse) is easily and accurately found at any increment during the deformation.

In comparison to the six spinel end‐members in the spinel prism, magnetic information on the intermediate spinel compositions is relatively poorly established. To investigate magnetic properties of intermediate compositions of Cr‐rich spinel, we collected 12 samples that might contain potentially magnetic Cr‐rich spinel. On the basis of chemical composition analysis and physical magnetic behavior, magnetic Group A Fe‐rich spinel (i.e., magnetite), magnetic Group B Cr‐rich spinel, and paramagnetic Group C Cr‐Al‐rich spinel were identified. Magnetite is solely responsible for the natural remanent magnetization (NRM) in severely serpentinized samples from intraoceanic island arcs, orogenic exposures of ultramafics, and back‐arc continental lithosphere settings. Magnetic Group B Cr‐rich spinel shows maximum unblocking temperatures of 200–280°C. Such temperatures permit Cr‐rich spinel to contribute to magnetic anomalies up to about 8–12 km in terrestrial lithosphere settings, given a normal geothermal gradient of 25 K/km. The existence of magnetic Cr‐rich spinel requires certain compositional conditions including a cation ratio of [Cr]/[Fe2++ Fe3+] from 1.33 to 1.56 as well as a low oxide ratio of (Al2O3+ MgO)/(Cr2O3+ FeO + Fe2O3) less than 10%. It is evident that compositions of spinels are related with the degree of serpentinization as Group A spinel is observed along the fractures between/among olivine grains in heavily serpentinized rocks. Spinels in Groups B and C seem to experience less severe metasomatic or hydrothermal alteration during serpentinization. Distribution of magnetic Cr‐rich spinel along the fractures of silicates (mostly olivine) may support a chemical origin of the NRM. Thus, Cr‐rich spinel is a potential NRM carrier and a source of magnetic anomalies in ultramafic complexes. Cr‐rich spinel with unblocking temperatures up to 200–280°C can contribute to magnetic anomalies in terrestrial lithosphere up to 8–12 kmMagnetic remanence carriers reflect the degree of metasomatic reaction associated with serpentinizationIntermediate compositions of Cr‐rich spinel with a cation ratio of [Cr]/[Fe2++ Fe3+] ranging from 1.33 to 1.56 can be magnetic

The Laguna del Maule volcanic field (LdMVF) in Chile, a rapidly inflating silicic volcanic system without historical eruption, is intersected by active regional faults. The LdMVF provides an opportunity to observe how faults influence, accommodate, or are driven by an actively deforming large silicic system. Here we use Compressed High Intensity Radar Pulse (CHIRP) acoustic reflection data to map the fault network in sediments captured within the eponymous lake at the LdMVF and combine our fault maps with the volcanic history, earthquake locations, focal mechanisms, and lacustrine magnetic data to interpret how faults and magmatism interact. Our seismic data image dominantly dip‐slip faults forming grabens within the lake, subparallel to regional faults. No indications exist in the seismic data to suggest that fault patterns were created by the volcanic system, either ring or radial faults. Fault strikes interpreted from seismic and magnetic data are consistent with mapped dike and fault orientations on land. We therefore interpret that active faults at the LdMVF are tectonic rather than volcanic in origin, forming a transtensional zone that hosts the magmatic system. However, vertical motion along a NS‐striking fault near the center of uplift suggests trapdoor‐style faulting above the volcanic center in which tectonic faults are reactivated to accommodate magmatic inflation and overlying deformation. Magnetic anomalies follow regional faults, suggesting that faults also provide migration pathways. Depositional patterns indicate a prior episode of uplift followed by quiescence, indicating that significant magmatically related uplift at the LdMVF can occur without an associated major eruption. Active normal faults subparallel to regional faults are imaged in the upper 20 m of lake sediments in the Laguna del Maule volcanic fieldGrabens within the lake are on trend with magnetic lineations and faults mapped on land, consistent with normal offset focal mechanismsFault‐facilitated localized doming and venting are present near the center of magmatic inflation

Explosive eruptions of large-volume rhyolitic magma systems are common in the geologic record and pose a major potential threat to society. Unlike other natural hazards, such as earthquakes and tsunamis, a large rhyolitic volcano may provide warning signs long before a caldera-forming eruption occurs. Yet, these signs--and what they imply about magma-crust dynamics--are not well known. This is because we have learned how these systems form, grow, and erupt mainly from the study of ash flow tuffs deposited tens to hundreds of thousands of years ago or more, or from the geophysical imaging of the unerupted portions of the reservoirs beneath the associated calderas. The Laguna del Maule Volcanic Field, Chile, includes an unusually large and recent concentration of silicic eruptions. Since 2007, the crust there has been inflating at an astonishing rate of at least 25 cm/yr. This unique opportunity to investigate the dynamics of a large rhyolitic system while magma migration, reservoir growth, and crustal deformation are actively under way is stimulating a new international collaboration. Findings thus far lead to the hypothesis that the silicic vents have tapped an extensive layer of crystal-poor, rhyolitic melt that began to form atop a magmatic mush zone that was established by ca. 20 ka with a renewed phase of rhyolite eruptions during the Holocene. Modeling of surface deformation, magnetotelluric data, and gravity changes suggest that magma is currently intruding at a depth of ~5 km. The next phase of this investigation seeks to enlarge the sets of geophysical and geochemical data and to use these observations in numerical models of system dynamics. [ABSTRACT FROM AUTHOR]

The article focuses on a study related to communication between field based geoscience and cyber-infrastructure communities. Topics include integration of datasets and models from geoscience subdisciplines for enhancing the knowledge of how the Earth works, proposal of a project "(EC3) Earth-centered communication for cyber infrastructure: Challenges of field data collection, management and integration" funded by the U.S. National Science Foundation (NSF), and engaging with computer scientists.