In 1969, when I was a student in California, there was a rash of predictions from astrologers, clairvoyants, and evangelists that there would be a devastating earthquake and the entire state—or at least a large part of it—would fall into the ocean. The seers claimed this would happen during April, although they were not in agreement about the precise date.

The geologic story of North America is a fascinating one. It’s also more than 4 billion years long—much more than we could ever hope to cover here. However, if you’re curious about the world around you, enjoy the big-picture perspective, and are interested in some of the processes that are constantly reshaping our planet, here’s a crash course on the basics. It’s a good place to start on your aerial tour of the continent’s most breathtaking landforms.

Geologists, also known as Geoscientists, are trying to understand the constitution of the earth. The surficial portion, which is directly visible to the geologists, is made up more of water bodies (the seas, the oceans, and the lakes, together constitute nearly 2/3rds of the entire surface of the earth) than the land masses (Africa, America, Asia etc.). Large area of land around the north and the southpoles, is covered with a thick blanket of ice sheet, throughout the year.

Compositional models of the Earth are critically dependent on three main sources of information: the seismic profile of the Earth and its interpretation, comparisons between primitive meteorites and the solar nebula composition, and chemical and petrological models of peridotite-basalt melting relationships. Whereas a family of compositional models for the Earth are permissible based on these methods, the model that is most consistent with the seismological and geodynamic structure of the Earth comprises an upper and lower mantle of similar composition, an Fe-Ni core having between 5% and 15% of a low-atomic-weight element, and a mantle which, when compared to Cl carbonaceous chondrites, is depleted in Mg and Si relative to the refractory lithophile elements.