Geophysics is a quantitative natural science that examines the physical processes and properties of the Earth. Geophysicists aim to understand the shape, gravitational and magnetic fields, internal structure and composition, and the surficial processes of the Earth. Many geophysical processes that we observe and experience on the surface of the Earth (like earthquakes and volcanism) are driven by the Earth’s interior.
Seismology is the scientific study of earthquakes and their environmental effects, such as tsunamis and landslides. Seismologists aim to understand where and why earthquakes occur where they do. One of the main pieces of evidence for plate tectonics was the observation that earthquakes tend to occur on plate boundaries where plates move relative to one another. Another aspect of seismology is the study of how the elastic waves generated by earthquakes travel through the Earth. Observations based on seismic waves and their recordings by seismic stations have provided evidence of the Earth’s structure, to include the fact that the Earth has an inner (solid) core and outer (liquid) core.
Geodesy is the science of extremely accurate measurements of Earth’s shape, gravity, and orientation—everything from the coordinate system that underlies all navigation and positioning to detecting the warning signs of a volcanic eruption. You may not have heard of the term “geodesy” before, but you’ve definitely benefited from it.
The tools of geodesy let us measure moving tectonic plates, rising sea level, shrinking glaciers, soil erosion after a wildfire, or groundwater overuse during a drought. Increasingly, they’re also being used for emerging applications like autonomous vehicles and precision agriculture.
Instruments that measure very precise positions using GPS satellites (or multiple satellite networks, more generally termed GNSS for “Global Navigation Satellite System”) are among those tools. There are also satellites that can measure tiny surface changes, like InSAR (Interferometric Synthetic Aperture Radar) satellites. And lidar devices on the ground or in the air use lasers to generate 3D imagery that also quantifies small changes over time. These are just some of the technologies that geodesists use to study our dynamic planet.
This section of our website is meant to help you learn more about all these techniques and applications of geophysics. Use the links below to learn more—either by starting with specific hazards or applications of geophysical tools, or by diving straight into a specific technology.