IELTS, ESP, EAP and CALL

An enormous mass of warm rock is rising slowly but steadily toward the surface of New England and for now, researchers cannot explain this kind of abrupt activity. "Our study challenges the established notion of how the continents on which we live behave," The upwelling we detected is like a hot air balloon, and we infer that something is rising up through the deeper part of our planet under New England.

London Lectures: Free public lectures

The search for flight MH370 has resulted in some of the most detailed maps of the deep ocean ever created, revealing the sea bed in incredible resolution.

Earth's inner core is thought to be solid, which means it should support shear waves. However, the small size of the inner core makes detecting shear waves very difficult. Tkalčić and Phạm correlated different types of seismic phases to finally determine the speed of shear waves in Earth's inner core (see the Perspective by Irving). The detection of the waves closes an 80-year quest to find them and confirms a solid, but soft, inner core.

Science , this issue p. [329][1]; see also p. [294][2]

Seismic J waves, shear waves that traverse Earth’s inner core, provide direct constraints on the inner core’s solidity and shear properties. However, these waves have been elusive in the direct seismic wavefield because of their small amplitudes. We devised a new method to detect J waves in the earthquake coda correlation wavefield. They manifest through the similarity with other compressional core-sensitive signals. The inner core is solid, but relatively soft, with shear-wave speeds and shear moduli of 3.42 ± 0.02 kilometers per second and 149.0 ± 1.6 gigapascals (GPa) near the inner core boundary and 3.58 ± 0.02 kilometers per second and 167.4 ± 1.6 GPa in Earth’s center. The values are 2.5% lower than the widely used Preliminary Earth Reference Model. This provides new constraints on the dynamical interpretation of Earth’s inner core.

[1]: /lookup/doi/10.1126/science.aau7649
[2]: /lookup/doi/10.1126/science.aav2296