Expert Report

Each report is produced by a committee of experts selected by the Academy to address a particular statement of task and is subject to a rigorous, independent peer review; while the reports represent views of the committee, they also are endorsed by the Academy. Learn more on our expert consensus reports.

Questions about the origin and nature of Earth and the life on it have long preoccupied human thought and the scientific endeavor. Deciphering the planet's history and processes could improve the ability to predict catastrophes like earthquakes and volcanic eruptions, to manage Earth's resources, and to anticipate changes in climate and geologic processes. At the request of the U.S. Department of Energy, National Aeronautics and Space Administration, National Science Foundation, and U.S. Geological Survey, the National Research Council assembled a committee to propose and explore grand questions in geological and planetary science. This report captures, in a series of questions, the essential scientific challenges that constitute the frontier of Earth science at the start of the 21st century.

Key Messages

  • Can earthquakes, volcanic eruptions, and their consequences be predicted? Thanks largely to sensitive new instrumentation and better understanding of causes, geologists are moving toward predictive capabilities for volcanic eruptions. For earthquakes, progress has been made in long-term forecasts, but we may never be able to predict the exact time and place an earthquake will strike.
  • How are Earth processes controlled by material properties? Deciphering the secrets of the rock record on Earth and other planets begins with the understanding of large-scale geological processes. The keys to understanding these processes are the basic physics and chemistry of planetary materials.
  • How did Earth and other planets form? While it is generally agreed that the Sun and planets all coalesced out of the same nebular cloud, it is still not known how Earth obtained its particular chemical composition, at least not in enough detail to understand its subsequent evolution or why the other planets ended up so different from ours and from each other. Further measurements of other Solar System bodies and extrasolar planets and objects appear to be the primary pathway to furthering our understanding of the origin of Earth and the Solar System.
  • How did life begin? When life first arose, the conditions at Earth's surface may have been much different than today's, and one critical challenge is to develop an accurate picture of the physical environments and the chemical building blocks available to early life.
  • How do fluid flow and transport affect the human environment? Much better models of streamflow and associated erosion and transport are needed if we are to accurately assess how human impacts and climate change affect landscape evolution and how these effects can be managed to sustain ecosystems and important watershed characteristics.
  • How does Earth's interior work, and how does it affect the surface? Although we know that the mantle and core are in constant convective motion, we can neither precisely describe these motions today nor calculate with confidence how they were different in the past.
  • How has life shaped Earth and how has Earth shaped life? The development of life has clearly been influenced by the conditions of Earth's surface, while Earth's surface has been influenced by the activities of life forms. But the exact ties between geology and evolution are still elusive.
  • What causes climate to change and how much can it change? Recent discoveries have highlighted periods of Earth history when the climate was extremely cold, was extremely hot, or changed especially quickly. Understanding these special conditions may lead to new insights about Earth's climate, as will new geochemical observations made on ancient sedimentary rocks and improved models for the climate system that will eventually enable us to predict the magnitude and consequences of climate changes.
  • What happened during Earth's dark age (the first 500 million years)? The so-called Hadean Eon is a critical link in our understanding of planetary evolution, but we have little information about it because there are almost no rocks of this age preserved on Earth. Clues about this time period are accumulating, however, as we learn more about meteorites and other planets and extract new information from ancient crystals of zircon on Earth.
  • Why does Earth have plate tectonics and continents? We still do not know when continents first formed, how they are preserved for billions of years, or exactly how they evolved to be what they are like today. New data and observations indicate that climate and erosion play a fundamental role in building and shaping mountain ranges and thus are fundamental to the formation as well as the destruction of continental crust.