When the Earth Moves (Spanish version, 2003)

Summary: The development of the seismograph enabled seismologists to detect and locate earthquakes and probe the interior of the planet. This knowledge led to the idea in 1915 that the seven continents were once one large land mass that broke apart creating the continents. Strong support of this idea did not come until the mid 1950's, when paleomagnetic data supported it. Scientists used sonar measurements to map the ocean floor, leading to the discovery of large undersea mountain ranges with midocean ridges. A suggestion that the seafloor was slowly spreading was confirmed by a magnetic survey of the material on either side of a midocean ridge. Examining the ridges and faults radiating from the ridges helped show that the earth's crust is made up of several plates. The understanding of plate tectonics has led to improved building methods in earthquake-prone areas. Maps of the earth's surface have also helped identify areas for mining and petroleum exploration. An unexpected bonus has been the discovery of entire new ecosystems that live near the hydrothermal vents, created by the spreading of the sea floor.