In the podcast, Cees Van Staal tells us about the Paleozoic tectonic events that led to the formation of the Appalachians. The events are closely related to those involved in the Caledonian orogeny and the mountains it created in what is now Ireland, Scotland, east Greenland, and Norway, as discussed in the episode with Rob Strachan. However, the Appalachians that we see today are not the worn-down remnants of the Paleozoic mountains. Instead, they reflect much more a topography that was created during processes associated with rifting and magmatism that accompanied the opening of the Atlantic Ocean as well as the effects of the ice ages as recently as about 10,000 years ago.

Van Staal has been studying the Appalachians for over 35 years, focusing especially on the large-scale tectonics of their formation. He is Emeritus scientist at the Geological Survey of Canada and an Adjunct/Research Professor in the Department of Earth and Environmental Sciences at the University of Waterloo in Ontario.

In previous episodes of Geology Bites, Barbara Romanowicz gave an introduction to seismic tomography and Ana Fereira talked about using seismic anisotropy to reveal flows within the mantle. In this episode, Andreas Fichtner explains how, despite the many fiendish obstacles that stand in our way, we are making steady improvements in our ability to image the Earth on both regional and global scales. These give us confidence that we can make three-dimensional maps of certain structures, such as the plume below Iceland, cold continental interiors, mid-ocean ridges, and the large low shear-velocity provinces.

Fichtner is a Professor in the Department of Earth and Planetary Sciences at the Federal Institute of Technology in Zurich.

When the Earth formed, it was covered by a hot magma ocean. So when and how did thick, silica-rich continental lithosphere form? Were the first, ancient continents similar to the present-day continents? And did the continents form in a burst of activity at a certain point, or was it a gradual build-up over Earth history?

In the podcast, Renée Tamblyn addresses these questions, as well as how early geological processes created molecular hydrogen that may have powered the first forms of life. In her own research, she has focused on the critical role played by water released from hydrous minerals that formed within oceanic lithosphere on the sea floor.

Tamblyn is a Postdoctoral Researcher at the University of Bern.