A typical magnetic sensor suite at an INTERMAGNET-standard observatory: (front) fluxgate variometer, (left) proton-precession magnetometer, (right) theodolite with small fluxgate attached to telescope.
Apparent polar wander path for North America for Late Carboniferous to recent time. The numbers represent time in millions of years before present. Circles represent one standard error about the mean. (After E. Irving, Paleopoles and paleolatitudes…
Map showing the tectonic structure of the Earth's lithosphere, which is composed of about 10 rigid plates, each moving as a distinct unit. (After J. F. Dewey, Plate tectonics, Sci. Amer., 226(5):56–68, 1972)
Geology of the North Atlantic Ocean. (a) Physiographic divisions of the ocean floor. (b) Principal morphologic features along the profile between North America and Africa. (Modified from B. C. Heezen et al., GSA Spec. Pap. 65, 1959)
Topography of the mid-oceanic ridge. (a) Mid-Atlantic Ridge (25°N), spreading rate 2.6 cm (1.0 in.) per year. (b) East Pacific Rise (55°S), spreading rate 8.8 cm (3.5 in.) per year; sea-level rises causing transgression (arrows). 1 km = 0.6 mi.