『Abstract
　Humans move increasingly large amounts of rock and sediment during various construction activities, and mean rates of cropland soil loss may exceed rates of formation by up to an order of magnitude, but appreciating the actual importance of humans as agents of global erosion necessitates knowledge prehistoric denudation rates imposed on land surfaces solely by natural processes. Amounts of weathering debris that compose continental and oceanic sedimentary rocks provide one such source of information and indicate that mean denudation over the past half-billion years of Earth history ha lowered continental surfaces by a few tens of meters per million years. In comparison, construction and agricultural activities currently result in the transport of enough sediment and rock to lower all ice-free continental surfaces by a few hundred meters per million years. Humans are now an order of magnitude more important at moving sediment than the sum of all other natural processes operating on the surface of the planet. Relationships between temporal trends in land use and global population indicate that humans became the prime agents of erosion sometime during the latter part of the first millennium A.D.

Keywords: denudation; erosion; humans; deep time.』

Introduction
Global Phanerozoic sediment fluxes
River basin sediment loads
Humans as geologic agents
Conclusions
Acknowledgments
References cited

Figure 1. Data from Ronov (1983) on volumes of sediment of given age deposited on oceanic (shaded) and continental (unshaded) crust. Dashed line is best-fit model of decrease in global volume of sedimentary rock under assumptions that mean oceanic and continental sediment fluxes are 1.1 and 2.3×106 km3/m.y., respectively ( y-intercepts), and sediment destruction by subduction and erosion of 2.28％/m.y. and 0.06％/m.y., respectively (see text). Figure 2. Continental denudation rates for epoch-long intervals determined from compositions of sedimentary rocks in Ronov (1983) and fluxes and cycling rates in Figure 1. Terrigenous debris makes up 69％ and chemically precipitated phases are 31％ of current 630×106 km3 of rock in global Phanerozoic sedimentary reservoir. Figure 3. Historical rates of anthropogenic erosion (open diamonds) from data in Hooke　(2000a). For comparison, solid black diamonds are volumes of several large volcanic eruptions (dates in parentheses); heavy black line is mean deep-time denudation rate of 24 m/m.y. determined from Figure 2.

Hooke,R.,LeB.(2000a): On the history of humans as geomorphic agents. Geology, 28, 843-846.
Ronov,A.B.(1983): The Earth's sedimentary shell: Quantitative patterns of its structure, compositions, and evolution. American Geological Institute Reprint Series, 5, 1-73.