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NARROW
GeoRef Subject
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all geography including DSDP/ODP Sites and Legs
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Central America
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Costa Rica
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Irazu (1)
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geologic age
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Cenozoic
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Quaternary
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Holocene (1)
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igneous rocks
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igneous rocks
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volcanic rocks
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pyroclastics (1)
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Primary terms
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Cenozoic
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Quaternary
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Holocene (1)
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Central America
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Costa Rica
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Irazu (1)
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education (2)
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igneous rocks
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volcanic rocks
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pyroclastics (1)
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plate tectonics (2)
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Factors influencing non-expert term usage during a disaster: An analysis of the 2004 Indian Ocean tsunami
Research methods and underlying theories for research designs that integrate quantitative and qualitative approaches (i.e., mixed methods) are well documented in the field of education research. What is missing in the literature is a nuts-and-bolts description of the actual practice that goes into creating a good mixed-methods survey instrument for research in the science education domain. This paper will detail the steps involved in designing, implementing, and scoring a valid and reliable mixed-methods survey instrument. This survey instrument was designed to investigate experts' and novices' conceptual understanding of plate tectonics as inferred by their answers to a series of questions related to a modified version of a commonly used cross-section schematic published by the U.S. Geological Survey. Development of the instrument involved numerous revisions with iterative inputs from local and community-based experts. After integration of expert comments, the survey instrument was piloted to a physical science for nonscience majors course. This led to further revisions in the survey instrument to improve communication validity prior to widespread distribution. Development of scoring rubrics similarly required iterative modifications based on a thematic analysis of collected data. By outlining the steps involved in designing, validating, and analyzing this mixed-methods instrument, we believe that this paper can serve as a template for future survey instrument development. In particular, we hope to illustrate the iterative and time-intensive nature of mixed-methods inquiry, both in terms of pre-investigation design and postinvestigation analysis, and to offer our empirically based insights into the instrument and rubric development process.
Counting tectonic plates: A mixed-methods study of college students' conceptions of plates and boundaries
We explored students' conceptions of plate tectonics using a combined qualitative and quantitative approach consisting of multiple-choice ConcepTest questions, questionnaires, and interviews. When shown schematic images illustrating plate tectonics, half of the students were unable to determine the correct number of tectonic plates. These students appeared to have the most difficulty determining whether or not to count a divergent boundary as a plate boundary, but additional difficulties include confusion between continent-ocean boundaries (shorelines) and plate boundaries, and failure to see the larger picture as a result of focusing on individual boundaries. We propose that the underlying causes for these difficulties stem from the tendency for students to construct their understanding of plate tectonics based on inappropriately applied prior knowledge. For example, when viewing a divergent boundary, many students activate two lines of prior knowledge: (1) if entities are the same (such as ocean plates on both sides of a divergent boundary) then they are not considered separate; and (2) if there is no obvious break (which is not seen on diagrams of divergent boundaries), then they are also not considered separate. The application of both of these lines of prior knowledge results in students concluding the two sides of a divergent boundary are the same plate. Retention of these alternative concepts prevents conceptual change from occurring during the period of instruction and results in students not recognizing divergent boundaries as plate boundaries, leading them to incorrectly count the number of plates.
We report the first detailed study of recent tephra deposits at Irazú volcano, Cos-ta Rica. These ash-fall deposits consist of unconsolidated, moderately to well-sorted, mostly juvenile ash of porphyritic basalt to basaltic andesite. Ash accumulations are thickest SW of the crater, an area that includes the headwaters of the Reventado River, which flows through the city of Cartago. With increasing eruption intensities, deposition shifts more westerly—toward the capital city, San José. Of seventeen historic eruptions, only two have left distinct ash deposits. At least eight other ash-fall deposits from the past 2600 yr are preserved on the SW flank of Irazú. Carbon-14 based correlations of deposits indicate that the ash accumulation rate has been relatively consistent during this period (e.g., ≈18 cm/century, 5 km SW of the crater). This consistency combined with the historic preservation ratio and correlated prehistoric deposits implies that Irazú may have erupted >85 times during the past 2600 yr. Most of these would have been small, volcanic explosivity index (VEI) ≤2 eruptions, with only ten or so VEI = 3 eruptions likely occurring every 200–400 yr. The largest historic eruption occurred in 1963–1965, and we estimate a minimum tephra volume of 3 × 10 7 m 3 for that eruption. The 1963–1965 eruption was not quite as energetic as some eruptions of the past 2600 yr, but it is of the same order of magnitude, and, based on its thickness, it approximates the size and duration of the larger eruptions of the past 2600 yr.