How do Earth scientists study rocks, water, air, and changes to Earth over time?

Earth scientists study the Earth, its waters, and the atmosphere by observing, describing, and classifying features to develop and test scientific hypotheses. Because many objects of study—such as deep rock layers or high-altitude air masses—are inaccessible, researchers rely on a three-dimensional perspective and the study of geologic time.1

Studying Rocks and Earth History

Geologists examine the physical and chemical makeup of the solid Earth, including minerals and rocks. To understand changes over time, they use stratigraphy and the law of superposition to determine relative ages. Radiometric dating and geochronology allow scientists to assign numerical ages to rocks and fossils, helping reconstruct Earth's 4.6-billion-year history.123

Studying Water and Air

Hydrologists study water on and within the ground, using techniques like measuring stream discharge and analyzing isotope tracers to understand water movement. Atmospheric scientists use physics, chemistry, and mathematical models to evaluate atmospheric structure and dynamics, ranging from daily weather forecasting to long-term climatology.145