USGS · 70033401
[No abstract available]
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D. A. John. 2008. Supervolcanoes and metallic ore deposits. https://doi.org/10.2113/gselements.4.1.22
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The hydrocarbon remnants of biologically diagnostic lipids inform our understanding of Earth’s early ecosystems, particularly where morphological vestiges of biology are absent or ambiguous. Yet both the analysis and interpretation of ancient biomarkers require scrutinous approaches. Here, we describe the status quo of Precambrian biomarker geochemistry with four examples that highlight current challenges and opportunities.
Volcanic activity is dictated by crustal pathways and reservoirs through which magma ascends and collects. The Cascades are a natural laboratory to study the variable influence of the crust on erupted magmas and subterranean reservoirs. The interaction of ascending magmas with the variable subduction geometry and tectonics of the overriding North American plate have given rise to a diversity of magmatic storage conditions. The confluence of geochemical and geophysical investigations emphasizes that most magmatic systems in the Cascades have been built at multiple levels in the crust as determined by tectonics, pre-existing structure, and magmatic flux from the mantle.
Subduction zones produce some of Earth’s most devastating geological events. Recent eruptions of Mount St. Helens and great earthquakes and tsunamis in Japan and Sumatra provide stark examples of the destructive power of subduction-related hazards. In the Cascadia subduction zone, large earthquakes, tsunamis, and volcanic eruptions have occurred in the past and geologic records imply that these events will occur in the future. As the population and infrastructure increase in the region, resilience to these natural hazards requires a detailed scientific understanding of the geologic forces and processes involved, combined with a society motivated to mitigate risks.