Columbia subject headings:
Continents.
Earth (Planet)--Crust.
Plate tectonics.
Seismic reflection method.
Seismic refraction method.
Seismology--Research.
Harvard subject headings:
Continents.
Earth (Planet)--Crust.
Plate tectonics.
Seismic reflection method.
Seismic refraction method.
Seismology--Research.
Princeton subject headings: