- How much horizontal slip did the United States Geological Survey measure along the San Andreas Fault after the 1906 earthquake?
- What did the State Earthquake Investigation Commission report accomplish for the field of seismology?
- How did the 1906 earthquake influence later building codes and civil engineering practices?
Geology and Earth Science
The physical structure, history, and processes of the Earth.
- What evidence did Alfred Wegener use in 1912 to argue that the continents had once been joined as Pangaea?
- Why did the geological establishment reject Wegener's continental drift hypothesis despite the coastline and fossil evidence?
- What mechanism, discovered decades later, finally explained how continents could move across the ocean floor?
- How did scientists eventually recover material to study the origins of the 1918 flu virus nearly a century later?
- Why does the sunspot cycle matter for forecasting geomagnetic storms that can disrupt satellites and power grids?
- How much stronger than Earth's gravity were the forces Svedberg's rotor generated, and why was that necessary?
- What does the 'Svedberg' unit measure, and why is it still used in molecular biology labs today?
- How did Bridgman's high-pressure data end up informing models of the Earth's mantle?
- What did scientists believe about the ocean floor before Ewing and Heezen's mapping work?
- How long is the Mid-Atlantic Ridge, and why did its scale surprise geologists in 1956?
- What did the central rift valley at the ridge's crest suggest about the seafloor being pulled apart?
- How did palaeomagnetic surveys in the early 1960s confirm the seafloor spreading hypothesis and make plate tectonics unavoidable?
- Why had Alfred Wegener's continental drift theory struggled to gain acceptance for decades before 1963?
- What did the symmetric magnetic stripes on either side of the Mid-Atlantic Ridge reveal about the ocean floor?
- How does newly formed basalt at a mid-ocean ridge record the direction of Earth's magnetic field?
- Why is the discovery sometimes called the Vine-Matthews-Morley hypothesis instead of just Vine-Matthews?
- How did Arecibo's design use a natural limestone sinkhole to support its 305-metre dish?
- How did geologists' evidence for Earth's true age create a problem for existing theories of solar power?
- What hypothesis led Thomas Brock to search Yellowstone's hot springs for life?
- What triggered the collapse of Mount St. Helens' north face on the morning of May 18, 1980?
- Why did the collapse of the volcano's north face produce a lateral blast rather than a typical vertical eruption?
- How did the 1980 Mount St. Helens eruption change how scientists assess volcanic eruption risk?
- Where had the evidence for the Chicxulub crater been sitting undetected for decades?
- What were the microscopic structures Okamura interpreted as miniature fossils actually made of?
- What are evaporites, and why do they indicate ancient saltwater on Mars?
- How did researchers determine that dogs align their bodies with the Earth's magnetic field while defecating?
- Why did the dogs' magnetic alignment preference disappear during periods of geomagnetic disturbance?
- How sensitive is InSight's seismometer, and what can it detect about marsquakes?
- Why does licking a rock make it easier for geologists to identify its texture and mineral content?
- What other concept is Jan Zalasiewicz known for in geology?
- What is the geoid, and why does an accurate model of Earth's shape matter for satellite navigation?
- How did Gladys West use computers at the Naval Surface Warfare Center to model Earth's gravitational anomalies?
- What happens to a GPS position fix if the underlying geodetic model of Earth's surface is inaccurate?