Science Opportunities - Basic Research Opportunities in Earth Science - page 32

few years before. Using lasers and spectral imagers, it is now possible to
map seafloor habitats and to determine whether the substrate is fixed or movable,
living or fossil. These data also provide a better basis for integrated three-
dimensional models of coastal ocean processes (e.g., tides, waves, currents). New
models that integrate land-related processes (e.g., groundwater flow, sediment
flux and storage, morphology of drainage systems and watersheds) are being used
to understand nutrient loading in the coastal zone, as well as the ultimate fate of
waste materials and pollutants in the ocean.
Tectonics, Climate, and Weathering
Topography, surface hydrology, sedimentation, and climate are intimately
related. For example, erosion of the Tibetan-Himalayan plateau is related to
precipitation and glacier development. Climate and hydrology interact to modify
the surface expression of tectonic events, which in turn influence the rate and
scale of fluvial responses. Topography exerts a major influence on erosion and
the subsequent deposition of sedimentary rocks, as well as the formation and
landscape diversity of soils. Similarly, removal of materials by surface processes
influences tectonic uplift rates. Coupled geologic-hydrologic-climate studies
promise a greater understanding of denudation rates, weathering processes, and
the survivorship of mountain ranges.
Earth History
The history of the planet is recorded in soils, sediments, ice, water, and
rocks. The geological record of environmental variations during the last several
hundred thousand years provides the context for understanding the current
climate system and its potential for future change. Important insights can also be
gleaned from the behavior of the Critical Zone over even greater spans of
geologic time: topographic relief, length of day, solar influx, and composition of
the ocean and atmosphere have all varied significantly in the past. A good
example, based on both careful geological field work and geochemical and
isotopic observations, is the recent suggestion that the Earth went through a series
of global glacial events (“snowball Earth”) about 750 million to 580 million years
ago. The implications of such severe climatic conditions and other extreme
events (e.g., extensive volcanism, meteorite impacts) for the evolution and
maintenance of life on Earth are the subject of ongoing debate, stimulating new
efforts to characterize extreme environmental conditions of the past.