PROCESS RATES: THE PRESENT NEVER WAS THE KEY TO THE PAST

As we learn more about the last Glacial, the Deglaciation and the Holocene, it is becoming evident that the human impact on geologic processes goes far back in time. The initial effects were extinctions of many animals that had survived the rigors of changing climates of the Quaternary. But it now appears that human activities made the climate of the early Holocene much more stable than that of older interglacials, allowing urban settlements and the development of what we call ‘civilization.’ Even the relatively minor perturbations of this period of climate stability, the Medieval Climate Optimum and the Little Ice Age, may be due to human population growth and declines through pandemics.

However, things changed after the Industrial Revolution. There has been an accelerating destabilization of conditions on the surface of the planet. Burning fossil fuels, first peat and coal, then petroleum and then natural gas to supply increasing energy needs, and the decimation of forests for the expansion of agriculture to supply food for a suddenly increasing population, have contributed CO₂ to the atmosphere at an unprecedented rate. Replacement of C₃ with faster-growing C₄ plants to increase agricultural output have modified the evaporation-precipitation balance leading to changes in regional climates. Proliferation of rice paddies and domestication of ruminant animals have replaced bogs and termites as major sources of atmospheric methane. Mining of rare metals and other resources have introduced nutrients and pollutants into rivers, lakes and the oceans at unprecedented rates. Humans have replaced weathering, erosion, winds and water as the major agents of movement of rock and sediment.

Like the change from laminar to turbulent flow in moving water, a change from predictable to chaotic behavior can be expected as geologic processes affecting the surface of the Earth accelerate - leading us toward an uncertain future.