Episode notes
Volcanic rift zone reorganization and massive underground magma chambers are required to solve the mystery of Mauna Loa’s Ninole Hills. Mauna Loa’s lava flows repave 90% of the surface every 4,000 yrs, finding 100,000 yr old rocks is a geological detective sleuthing game.
Dr. Jeffrey Zurek (P.Geo) marks the 10 yrs of his research in Geophysical Research Letters by diving into the geophysics of Hawaii. Using high-precision Bouguer gravity mapping, he reveals how catastrophic mass wasting events can knock a volcanic rift zone off its axis, preserving ancient topography and reshaping the evolution of basaltic island volcanism.
Topics
The Survival of the Ninole Hills: Why these ancient outcrops shouldn't exist on the surface of this active shield volcano
Gravity Anomalies Explained: How "boxes with springs" allow geophysicists to detect high-density olivine crystal accumulations
Failed vs. Migrated Rifts: Mauna Loa’s southwest rift zone likely once had a completely different orientation
Landslide Trigger: Mass wasting 600 cubic kilometers can geologically "instantly" shift a volcano’s internal stress regime
Chapters
(00:00) 10-Year Anniversary My Research
(02:40) Hotspots: Stationary Plumes vs. Moving Plates
(03:45) Basics of Isostasy: The Pool Floaty Model
(05:10) Convection, Ridge Push, and Slab Pull
(06:50) Shear Waves: How We Know the Mantle is Solid
(08:30) 90% of Mauna Loa's Surface is less 4000 yr old
(12:30) The Subsurface Density of the Ninole Hills
(14:45) Anatomy of a Rift Zone: Intrusions and Instability
(16:20) Dismissing the Proto-Volcano Hypothesis
(18:30) Fieldwork in Hawaii: Gravimeters and GPS
(20:15) Settling Olivine: Signature of Magma Chambers
(22:00) Triple Junction Physics: Rifts Prefer 120 Degrees
(23:45) Kilauea’s East Rift: Asymmetric Gravity Signals
(25:30) Geologically Instantaneous Migration Events
(28:00) West Flank Landslides: 240,000 yrs ago
(30:15) Comparing Mauna Loa to Tenerife’s Angara Volcano
(31:45) Impact on Global Island Volcanism
(32:30) Volcanic Faults: The Dad Joke Segment
Links
HVO: https://www.usgs.gov/observatories/hvo
Research Paper doi: 10.1002/2015GL065863
Email: whimsical.wavelengths@gmail.com
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Whimsical Wavelengths: Deep-dive conversations where a working scientist unpacks how we know what we know, one paper, one idea, or whimsical detour at a time. Hosted by Dr. Jeffrey Zurek (P.Geo).