Paleo-Critical Zones, windows into the changing life and landscapes during the Quaternary Period

The Critical Zone (CZ) as visualized in 1998 was a way to integrate the research of the four scientific spheres (lithosphere, hydrosphere, biosphere and atmosphere) at the surface of Earth and to study the linkages, feedbacks and record of processes. Rather than closeting studies by a variety of disciplines into their respective pigeonholes the CZ perspective provides the symbiotic framework from which the tendrils of improved understanding can radiate outward to new disciplines and/or feedback into the component disciplines. During the last 2 decades, CZ research has been limited to the modern environment. Knowledge gained from the modern and the focus on interpreting ancient records allows for the development of paleo-CZs (PCZs). PCZs provide a powerful tool for improved understanding of the landscapes during the Quaternary Period and the response of this thin skin to glaciations, sea level fluctuations and evolving life. Case studies from hominins in East Africa and Homo sapiens in the Americas provide examples of the rich records stored in PCZs. As we move into the space age, the CZ can provide a platform from which to guide future exploration of the proto Critical Zones on the rocky planets and asteroids of our solar system.