Session 7 — Inside the Planet: What We Know, What We Don’t#
Format C — Relevance Map Week 7 Relevance: Cascades volcanism · Sea level · Geothermal
PREM and its limits · Cascades volcanism · Glacial isostatic adjustment
Hook (0 – 7 min)
Show the PREM velocity profile alongside a seismic tomography image of mantle plumes under Yellowstone. Ask:
“PREM is a 1D model. This tomography image is 3D. What does the difference tell you — and what could you never learn from PREM alone?”
Let students argue the contrast for 3 minutes before moving on.
Discussion (7 – 42 min)
Three groups, three problems. 12 minutes of group work, then 3-minute reasoning presentations.
Group A — Cascade volcanoes: Why do the Cascades have volcanoes? What does earth interior structure tell you about where the magma comes from, and what method would you use to image the subducting slab?
Group B — Glacial isostatic adjustment and sea level: Sea level projections depend on how Earth’s mantle responds to ice sheet melting (glacial isostatic adjustment). How does seismology connect to sea level science? What Earth interior properties matter?
Group C — Geothermal prospecting: A geothermal company wants to know if there is a heat source at depth in a new area. How does PREM constrain where they should look?
After each presentation: “What assumption in your reasoning would most change your answer if it were wrong?”
Relevance
Basic science: Everything we know about the Earth’s liquid outer core, solid inner core, and 660-km phase transition came from seismology alone — no drill reaches any of it.
Climate: Glacial isostatic adjustment (GIA) — how the solid Earth rebounds after ice melts — is embedded in every IPCC sea level projection. The earth interior physics from this week affects where coastlines will be in 2100.
Energy: Geothermal energy development in the western US depends on seismic imaging of magmatic systems and heat flow models grounded in earth interior knowledge.
Go Deeper
IRIS “EarthScope and the Dynamic Planet” resources · Milne & Mitrovica (2008) on GIA and sea level
One name: Dr. Eric Ivins, JPL — solid Earth / ice sheet coupling. His group works at exactly the intersection of seismology and climate science.