Monthly Archives: October 2015

Seawater isotope ratios through time: sulfur and carbon

Low sea levels = heavy carbon, light sulfur in seawater

  • Low sea levels = more land space for plants = plants use lighter carbon = lighter carbon stuck on land = heavy carbon in the sea!
  • Low sea levels = less habitat for sulfate-reducing bacteria = less light sulfur in pyrite = more light sulfur in the sea!

High sea levels = light carbon, heavy sulfur in seawater

  • High sea levels = less space for plants = less light carbon uptake by plants = light carbon in the sea!
  • High sea levels = expanded habitat for sulfate-reducing bacteria = more light sulfur in pyrite = less light sulfur in the sea!

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Subducted seawater the source of fluid-rich diamonds

Subducting oceanic plates that dive hundreds of kilometers beneath Earth’s surface carry with them cargoes of sediment and seawater. As the plate heats up the deeper it sinks, this seawater not only initiates melting in the rock above it, but can also trigger diamond formation, suggest the authors of a new study in Nature. Read more

How the west was made: western North American orogenies

Western North America is a patchwork is hundreds of terranes, which are crustal pieces or microplates (think of islands), that collided with and attached to North America across hundreds of millions of years -- adding piece-by-piece to the continent's width and building mountains as they produced volcanoes or pushed up sediments and rocks. This posts provides a very simplified timeline of the major orogenies and terranes that affected western North America. For a more in-depth look, see the resources below. Read more