Inside Earth

Earthquakes, explosions, pyroclastic flows, and tsunamis can result from oceanic volcanic activity, both from underwater and island volcanoes. Documenting these volcanic edifices and ash flows resulting from eruptions is important in mitigating the resulting hazards to nearby residents. Ocean explorers at GSO routinely discover and map volcanic regions and associated ash flows using Remotely Operated Vehicles (ROVs) for a better understanding of the tectonic processes at work and importantly, to document biological activity around vents and seeps associated with the volcanism.

GSO geologists use a deep-diving submersible to collect samples for analysis back at the laboratory to uncover processes taking place at the margins of the large tectonic plates making up Earth’s crust. The plates plunge down into Earth’s mantle at subduction zones. Study of the fate of the volatiles such as CO2 and H2O carried on the crustal plates as they descend into the mantle leads to an understanding of the coupling of the crust and exosphere (ocean and atmosphere) in the whole-Earth system.

Many features on the surface of Earth can be attributed to activities in Earth’s mantle. For example, the Hawaiian island chain and Iceland are products of mantle melting above hot-spots, or, as many geologists believe, from a rising diapir (a column of rock moving upward piercing surrounding layers) of mantle called mantle plumes. Simulation of mantle dynamicism in the laboratory requires an understanding of the thermodynamic environment in the mantle. GSO geologists carry out these experiments in a fluid that in a short time period can simulate the long-term movements of these rising diapirs. These fluid dynamic experiments have explained the unusual distribution of volcanism associated with the Yellowstone hot spot. Studies such as these help us understand how Earth works on a global scale.

From the GSO Seismology Lab
Using compressional-to-shear wave conversions at the 410- and 660-km mantle discontinuities, it was discovered that the transition zone between the two discontinuities is 20 km thinner than in the average Earth beneath central and southern Iceland but is of normal thickness beneath surrounding areas, a result indicative of a hot and narrow plume originating from the lower mantle. Image from GSO Seismology Lab.

Understanding where mantle plumes originate is a major geological question of the past decade. Do plumes begin deep in the mantle or do they develop in shallower regions? For the mantle plume responsible for Iceland, one GSO seismologist has the answer. Data from earthquake seismic wave travel speeds allows for constructing a computer-generated tomographic image of Earth below Iceland, much like a physician uses x-rays to image a human body in a CAT scan. The answer? The mantle plume beneath Iceland comes from deep in Earth’s mantle. Discoveries such as this offer a better idea of how our globe functions.

Geologically, the ocean floor is remarkably diverse, consisting of huge mountain ranges, fissures, and fracture zones where crustal tectonic plates are spreading apart. Deepbasins, volcanoes, and folded sediments exist where the plates are converging. Satellite gravity sensors and ship-based magnetic and multi-beam (sonar) surveys allow GSO scientists to “view” and map undersea features associated with plate tectonics to relate a story about their origins and fate and the movements of large sections of Earth’s crust as it recycles back into Earth’s mantle.

The Deep Carbon Observatory (DCO) is a global, ten-year research program to transform our understanding of carbon in Earth. At its heart, DCO is a community of scientists, from biologists to physicists, geoscientists to chemists, and many others whose work crosses disciplinary lines, forging a new, integrative field of deep carbon science. GSO scientists play active roles in the Deep Life and Reservoirs and Fluxes Communities associated with DCO, and the Office of Marine Programs serves the home to the program’s internationally-focused Engagement Team.