Even though it is nearly 5 billion years old, the earth is still active, and landscapes are constantly changing. The majority of continental rocks have been explored, studied, or sampled. The principle of uniformitarianism—also known as “the present is the key to the past”— is still applicable. Ancient rocks show textures that can be seen forming today from processes such as volcanic eruptions, earthquakes, hot springs, wind, weathering, river action, sedimentation, and erosion.
Technology now allows scientists to probe far deeper than Hutton or Lyell could centuries ago. Underwater cameras, microscopes, geophysical equipment, analytical techniques, sensing devices, and drilling advancements have allowed us to better determine how rocks form. Scientists use uniformitarianism to apply this knowledge to older rocks to better understand the complex history of the earth.