How deep and how steady is Earth’s surface?

Abstract

863 Weathering is the ubiquitous hallmark of the interaction of rock with environmental conditions on Earth’s surface. Alteration of fresh rock both releases nutrients to organisms and consumes atmospheric CO 2 . The disaggregated products of weathering provide substrate to anchor roots, and their production is the fi rst step in sculpting landscapes. The porosity structure developed by weathering retains water and paces its fl ow back to the oceans. For all these reasons, we care a great deal about the rates of weathering, how deeply below the surface a rock is weathered, and if this zone of weathering is steady or changing in time. Understanding the connections between weathering rate and erosion rate is a long-lived question in the study of Earth’s surface, and inevitably requires knowledge of the depth to which weathering processes reach and the rates of these processes over time. The balance between the downward penetration of weathering agents (atmospheric fl uids and organisms) and the damage they cause, and the removal of weathered material by erosion integrated over time, governs the thickness of the weathered zone. One