From coastal traces to earthquake histories
Meeting 3 of 13
Drafted v0.4 · not yet held · record discussion
Central question
When do geological traces discriminate a causal history, and when can different processes produce similar deposits?
Anchor and companion
- Everyone reads the selected anchor sections and the companion abstract/overview. The rotating reader presents the companion in depth.
- Pairing: Discovery claim / diagnostic scrutiny. Full records and access notes: bibliography.
Anchor
Atwater, B. F. (1987). Evidence for great Holocene earthquakes along the outer coast of Washington state. Science, 236(4804), 942–944. https://doi.org/10.1126/science.236.4804.942
Read Atwater in full.
Companion
Nelson, A. R., Shennan, I., & Long, A. J. (1996). Identifying coseismic subsidence in tidal-wetland stratigraphic sequences at the Cascadia subduction zone of western North America. Journal of Geophysical Research: Solid Earth, 101(B3), 6115–6135. https://doi.org/10.1029/95JB01051
Read Nelson and colleagues’ abstract, discussion of diagnostic criteria, and conclusions; the discussant examines the detailed examples.
Why these readings belong together
Atwater presents evidence for great past earthquakes. Nelson and colleagues examine how to distinguish coseismic subsidence from processes that also occur on passive coasts. This is refinement of the inference, not a blanket rejection of the discovery. (Atwater 1987; Nelson et al. 1996)
Prepare and discuss
Read the selected anchor sections and the companion abstract or overview. Bring one source passage or artifact relevant to the case; the rotating reader presents the companion in depth.
- Which observations are directly measured and which quantities are reconstructed?
- What would make a peat-mud contact insufficient evidence by itself?
- What new trace would distinguish competing interpretations?
Case exercise: scientific gain and epistemic mode
Construct rival coastal histories and identify the next trace that could discriminate among them. State shared assumptions, the supported scope, and what later evidence changed.
- Profiles to examine: synthesis, hypothesis, observation.
- Record source kind and unknown chronology; distinguish documented practice, philosophical argument, association, and our proposed agent rule.
- Ask what was gained, what warrants it, which action helped, and what a comparable agent would need to demonstrate.
The agent
- After the meeting, say what these papers change in the unit skill, agents/skills/unit-of-inquiry/SKILL.md: a rule at a node, a new composition of units, or a planted flaw. Meeting 1’s page shows the form.
- Modes exercised here, whose “agent actions” sections the rule would enter: synthesis, hypothesis, observation.
- Written from the texts after the papers are read in full, as for meeting 1; nothing here yet.
Optional extensions
- Satake et al. (1996): Time and size of a giant earthquake in Cascadia inferred from Japanese tsunami records of January 1700. Nature (1996). The independent trace that dated the event Atwater inferred: written records from Japan and tsunami modelling, with no Cascadia geology in the argument. Cleland’s smoking gun, found in another country’s archive.
- Yamaguchi et al. (1997): Tree-ring dating the 1700 Cascadia earthquake. Nature (1997). A third line of evidence, from the rings of drowned cedars, that converges on the same winter. The three papers together show what convergence of independent traces looks like, and how many competences it borrowed; see meeting 11.
- Bond et al. (2007): What do you think this is? “Conceptual uncertainty” in geoscience interpretation. GSA Today (2007). 412 geoscientists interpreted the same seismic section; their interpretations varied with their training and experience. The base rate for the variability the trace-inference mode has to live with.
- Polson and Curtis (2010): Dynamics of uncertainty in geological interpretation. Journal of the Geological Society (2010). How expert judgment in interpretation moves, drifts, and settles, followed over time.
- Baddeley et al. (2004): An introduction to prior information derived from probabilistic judgements: elicitation of knowledge, cognitive bias and herding. Geological Society, London, Special Publications (2004). Eliciting geological prior knowledge from experts, and the herding and cognitive bias that come with it.
- Rudwick (1985): The Great Devonian Controversy: The Shaping of Scientific Knowledge among Gentlemanly Specialists. University of Chicago Press (1985). The classic close study of how a body of geological knowledge was argued into being, from correspondence and notebooks. The model for reconstructing a trajectory rather than accepting a narrative.
- Currie (2018): Rock, Bone, and Ruin: An Optimist’s Guide to the Historical Sciences. MIT Press (2018). What the historical sciences, paleontology and geology among them, can know and how they know it, against the pessimism about traces.
Record after the meeting
Sign and date the notes; preserve disagreements and what changed your assessment. Keep confidential examples in private notes.