Description:
About intentional earth movement by humanity
Human's have been engaged in intentional movement of earth materials (rock, minerals, ores, sand, gravel, mud, clay, etc.) since the first hominids strode the Earth 3-4 million years ago. Rocks to make tools and shelter, ores refined for metals, and aggregate for roads and buildings have all been transported by humans in a deliberate fashion. As the human population has increased to its present 6 billion and counting, the amount of earth materials moved by the world population has also increased. And now, human beings are considered to be a significant geologic agent, changing the morphology or form of the land. Human beings are geomorphic agents much like rivers, waves, wind, and glaciers.
What impact have humans had on the transportation of earth materials? Hooke (2000) has compiled some estimates of mass transport by various civilizations over time. The estimates are given in the table and graph, with time given as thousands of years (kiloyears or ka) since the building of the Egyptian Pyramids, and earth materials moved given in metric tonnes per capita per year. Thus Hooke (2000) not only compiled estimates of mass moved, he also compiled estimates of the time it took to move that mass and the size of the population that moved it (to get this rate ).
The student should appreciate the many uncertainties in making these estimates. Some estimates are probably fairly reliable, despite their antiquity; much is known about the mass of the Egyptian pyramids and monuments and the time it took to make them. However, what of the other cultures on Earth 4,500 years ago, when the Earth's population was approximately 1 million? The absence of pyramids from these other cultures does not rule out significant earth movement. Note also that Hooke (2000) is compiling information from many sources, and there are always problems generated by doing so.
The data show an expected pattern; humans are moving significantly more earth materials per capita today than in the past, reflecting highly industrialized cultures that consume mass quantities of everything. Students can try fitting an exponential model to the data; this model will not only yield a low correlation coefficient, but will not give a good "shape" to the regression line. Students could generate their own models which give better curve shapes. What will be the per capita rate of earth movement in 100 years for the USA and the World?
Note that unintended soil movement associated with erosion of agricultural lands is not included in these data. Unintended mass movement has been about 2-10 times that of intentional earth modification.
