environmental geology edward keller pdf download

Down-plated slabs are overpassed by advancing arcs and plates, and thus transferred to enlarging oceans and backarc basins.

Broadside-sinking slabs push all sublithosphere oceanic upper mantle inward, forcing rapid spreading in shrinking oceans. Slabs sink more steeply than they dip and, if old and dense, are plated down on the 660 km discontinuity. Subduction rights the density inversion that is produced when asthenosphere is cooled to oceanic lithosphere: plate tectonics is driven by top-down cooling but is enabled by heat. The behavior of arcs and the common presence of forearc basins on the uncrumpled thin leading edges of advancing arcs and continents are among features indicating that subduction provides the primary drive for both upper and lower plates. These and other first-order features of global tectonics cannot be explained by conventional models. The Pacific spreads rapidly yet shrinks by rollback, whereas the subduction-free Atlantic widens by slow mid-ocean spreading. Subduction-hinge rollback is the key to viable mechanisms. Popular models that present plate tectonics as being driven by bottom-heated whole-mantle convection, with or without plumes, are based on obsolete assumptions, are contradicted by much evidence, and fail to account for observed plate interactions. Photo by the Author.Ī conceptual shift is overdue in geodynamics. Notice how rugged the Clark's Fork Canyon gets as it exits the mountains. PreCambrian of the high Beartooth Uplift in the background, with the canyon of the Clark's Fork in front of it. Even more subtle, you can see the switchbacks on the Dead Indian access road on the left (shaded and wooded) side of the transgressive ramp -where the picture with Antelope Mesa was taken from. If you look carefully you can see bright little cliffs of west dipping Paleozoic carbonates, sitting on the transgressive ramp. Heart Mountain had to have been transported from west of this view up across the monocline and came to rest on the younger sediments several miles to the east.

Antelope Masa and the moved blocks still on the bedding plane segment of the detachment, are a few miles to the west of this view. The forested west-facing slope of this view contains the same strata seen in Heart Mountain, several miles to the east. Aerial view north along the monocline that separates the Beartooth Mountain block, and the bedding plain segment of the detachment surface south of it, from the Bighorn basin on the right.

Environmental geology edward keller pdf download