A lithospheric instability origin for Columbia River flood basalts and Wallowa Mountains uplift in northeast Oregon

Article Abstract:

The elevation of the interface between Columbia River basalts (CRB) and other geological formations indicate that mild pre-eruptive subsidence took place in the Wallowa Mountains. After studying the seismic velocity structure of the mantle underlying this region and erosion corrected elevation maps, it is concluded that convective downwelling and detachment of a compositionally dense plutonic root can explain the timing and magnitude of CRB magmatism, as well as the surface uplift.

Oregon, Environmental aspects, Uplift (Geology), Columbia River Gorge

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What's on the plume channel?

Article Abstract:

Geochemical anomalies in the mid-ocean ridge basalts (MORB), which are compositionally alike, indicate the presence of a near-ridge hotspot. The plume-jet model postulates that the plume rises to the ridge as a single jet and disperses along it. Several geophysical data support this model. Moreover, the helium isotope composition of MORB is determined by physical processes occuring within the mantle as the plume-derived material migrates to the melting zone below the ridge axis.

Mid-ocean ridges

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When crust is bred

Article Abstract:

The helium-isotope ratios in basalts found in oceanic islands and derived from Earth's mantle are studied. The results of this analysis might prove to be very important for understanding some of the most distinctive volcanic features on Earth.

United States, Methods, Usage, Geochronology

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