Alfred Wegener in the context of "Bergeron process"

The Isthmus of Panama, historically known as the Isthmus of Darien, is the narrow strip of land that lies between the Caribbean Sea and the Pacific Ocean, linking North and South America. The country of Panama is located on the isthmus, along with the Panama Canal. Like several isthmuses on Earth, as a relatively narrow land bridge between close seas, it is a location of great geopolitical and strategic importance.

The isthmus is thought to have finally formed around 3 million years ago (Ma), separating the Atlantic and Pacific Oceans and causing the creation of the Gulf Stream, as first suggested in 1910 by Henry Fairfield Osborn. Osborn based the proposal on the fossil record of mammals in Central America, a conclusion that would provide a foundation for Alfred Wegener when he proposed the theory of continental drift in 1912. Some recent studies suggest an earlier formation of the isthmus than the recognized age of 3 Ma, potentially stretching as far back as 19 Ma.

Continental drift is a highly supported scientific theory, originating in the early 20th century, stating that Earth's continents move or drift relative to each other over geologic time. The theory of continental drift has since been validated and incorporated into the science of plate tectonics, which studies the movement of the continents as they ride on plates of the Earth's lithosphere.

The speculation that continents might have "drifted" was first put forward by Abraham Ortelius in 1596. A pioneer of the modern view of mobilism was the Austrian geologist Otto Ampferer. The concept was independently and more fully developed by Alfred Wegener in his 1915 publication, "The Origin of Continents and Oceans". However, at that time his hypothesis was rejected by many, largely because there was no known geological mechanism which could propel such massive movements. In 1931, the English geologist Arthur Holmes proposed mantle convection for that mechanism, which is now known to be powered by radioactive decay and primordial heat and a much smaller amount of heat from tidal heating.

The Conrad discontinuity corresponds to the sub-horizontal boundary in the continental crust at which the seismic wave velocity increases in a discontinuous way. This boundary is observed in various continental regions at a depth of 15 to 20  km, but it is not found in oceanic regions.

The Conrad discontinuity (named after the seismologist Victor Conrad) is considered to be the border between the upper continental (sial, for silica-aluminium) crust and the lower one (sima, for silica-magnesium). It is not as pronounced as the Mohorovičić discontinuity and absent in some continental regions. Up to the middle 20th century, the upper crust in continental regions was seen to consist of felsic rocks such as granite (sial), and the lower one to consist of more magnesium-rich mafic rocks like basalt (sima). Therefore, the seismologists of that time considered that the Conrad discontinuity should correspond to a sharply defined contact between the chemically distinct two layers, sial and sima. Despite the fact that sial and sima are two solid layers, the lighter sial is thought to "float" on top of the denser sima layer. This forms the basis of Alfred Wegener's 'Continental Drift Theory.' The area of contact during the movement of the Continental plates is on the Conrad discontinuity.

George Gaylord Simpson (June 16, 1902 – October 6, 1984) was an American paleontologist. Simpson was perhaps the most influential paleontologist of the twentieth century, and a major participant in the modern synthesis, contributing Tempo and Mode in Evolution (1944), The Meaning of Evolution (1949) and The Major Features of Evolution (1953). He was an expert on extinct mammals and their intercontinental migrations. Simpson was extraordinarily knowledgeable about Mesozoic fossil mammals and fossil mammals of North and South America. He anticipated such concepts as punctuated equilibrium (in Tempo and Mode) and dispelled the myth that the evolution of the horse was a linear process culminating in the modern Equus caballus. He coined the word hypodigm in 1940, and published extensively on the taxonomy of fossil and extant mammals. Simpson was influentially, and incorrectly, opposed to Alfred Wegener's theory of continental drift, but accepted the theory of plate tectonics (and continental drift) when the evidence became conclusive.

He was Professor of Zoology at Columbia University, and Curator of the Department of Geology and Paleontology at the American Museum of Natural History from 1945 to 1959. He was Curator of the Museum of Comparative Zoology at Harvard University from 1959 to 1970, and a Professor of Geosciences at the University of Arizona from 1968 until his retirement in 1982.

Otto Ampferer (1 December 1875 in Hötting near Innsbruck – 9 July 1947) was an Austrian alpinist and geologist. To explain the complex processes of Orogeny, he developed his "theory of undercurrent" with the idea of a partially plastic deep Earth's crust (asthenosphere). He became – even before Alfred Wegener – the pioneer of the modern view of continental drift.