In my last post I tried to explain the fundamentals of delamination. I used a floating wooden board being weighed down by metal as an analogy for the state of the Earth’s lithosphere. In the Earth, the crust is buoyantly floating on top of the mantle and is being weighed down by cold mantle material stuck to its bottom. If the two materials were to separate, the cold mantle material would sink off in to the warmer mantle below and the buoyant crust would rebound, rapidly building mountain ranges. So, in the most general sense, delamination refers to the process of heavy material peeling of the lithosphere and sinking down in to the mantle. This can be manifested in a few different forms.
The first form I’ll mention is the one which most resembles the analogy I gave before. In this case the cold mantle lithosphere peels back from the crust and sinks away in to the mantle (Figure 1). Hotter mantle material from deeper in the Earth replaces the cold lithosphere as it recedes.
Figure 1. Mantle lithosphere can peel off from the base of the crust, forcing hotter mantle to flow in to its place.
This sort of thing is most likely happening beneath the edges of the Colorado Plateau, contributing the dish-like shape to its edges . Whether or not this is actually the case is a contentious question but the evidence is convincing enough to mention it here.
Secondly, it is possible for the mantle lithosphere to drip off, with similar shape to the form which cold wax at the top of a lava lamp takes as it convects back toward the bottom. This is known as a “Rayleigh-Taylor Instability.”
Figure 2. Mantle lithosphere can drip off of the crust as a Rayleigh-Taylor instability.
This appears to have happened as a late stage in the formation of the Wallowa Mountains in northeastern Oregon .
Lastly, lithosphere can be forced to depth by horizontal tectonic forces from the plates. In this case, the lithosphere isn’t really delaminating because of its own inherent density instability, but because it is being pushed to depth by the material above it.
Figure 3 Horizontal tectonic forces can push lithosphere deep in to the mantle.
This is apparently the case for lithosphere beneath the transverse ranges of southern California, around the Los Angeles basin for instance .
My research is focused on understanding the mechanisms that enable each of these processes to happen. Assuming the mantle lithosphere is always buoyantly unstable, can it actually ever stably stick around? Is delamination the exception or the rule? And what controls whether the lithosphere will drip off in small Rayleigh-Taylor stabilities or in massive intact slab roll-backs.
All of these questions have impacts on, and feedback from other, associated tectonic and magmatic processes. I’m interested in untangling the causes and effects of each of these mechanisms and placing them in real-world context using the western US as a natural laboratory. All of my experiments have already been run for me, I just need to sort out what happened.
 Levander, A., et al. “Continuing Colorado plateau uplift by delamination-style convective lithospheric downwelling.” Nature 472.7344 (2011): 461-465.
 Darold, Amberlee, and Eugene Humphreys. “Upper mantle seismic structure beneath the Pacific Northwest: A plume-triggered delamination origin for the Columbia River flood basalt eruptions.” Earth and Planetary Science Letters 365 (2013): 232-242.
 Houseman, Gregory A., Emily A. Neil, and Monica D. Kohler. “Lithospheric instability beneath the Transverse Ranges of California.” Journal of Geophysical Research: Solid Earth (1978–2012) 105.B7 (2000): 16237-16250.