By K. Nepsa
Understanding geologic importance
Why is geology so important for us to understand? What is it about the Earth’s layers of rock and soil that can help us understand our past better as well as predict our future, as a planet? This is Part 1 of understanding “rad rocks.”
Geologic Interactions with the
Living Community
Scientists at the Arizona-Sonora Desert Museum did a great job of explaining the topic of “geologic importance” and according to them, the geology or the interpretation of earth and life’s history encompasses much more than the study of rocks. Continents, oceans, the climate, our atmosphere, and all life have co-evolved on this planet in a complex, interwoven web. Inorganic environmental changes occur, and all life forms must adapt quickly in terms of geologic time. There are many ways the earth may influence a local ecosystem. The least obvious is slow continental drifting across lines of latitude or longitude which affects circulation patterns in the oceans, storm tracks, mean temperatures, and the timing and duration of seasons.
Mountain chains appear near coastlines for various geologic reasons, setting up orographic (mountain-induced) cooling of rising moist air masses to form coastal fog deserts and rain shadow deserts on the protected sides, such as coastal Baja California and the hyper-dry Mohave Desert, respectively. Upland canyons, piedmonts, and mountaintops create new ecological niches, sites of adaptations and evolutionary change. The Sonoran Desert and nearby mountain islands exhibit nearly two miles of vertical relief, from sea-level deserts to mountaintops at 9500 feet (2900 m) that harbor sub alpine spruce-fir forests, cool enough to have supported semi-permanent ice masses on shady north slopes during the Pleistocene (the past two million years). Then, as mountains slowly erode to flatlands, the climate pattern changes.
As climates and habitats change plant and animal species either adapt, migrate to more favorable ground, or become extinct. Migratory routes are often determined by geologic processes. For example, climate dictates whether a river will be perennial or intermittent and whether a lake expands or dries up. New mountains produce new rivers. These changes may block or expedite migration for a terrestrial animal while serving as barriers or corridors for an aquatic one.
Ancient life affects later geologic and climatic conditions. Biologically produced gases (oxygen, carbon dioxide, methane, nitrous oxide) maintain a chemically reactive atmosphere that in turn influences rates of rock weathering, the nature of sedimentary deposits, and the content of gases in the atmosphere.
Desert soils, highly variable in their water-holding capability, salinity, and alkalinity determine the kinds of plants that will survive on them. Some desert plants, for example, are well-adapted to soils that would be toxic to other plants. A little geologic shift here and there…and voila…entire ecosystems can change. Next month is Part 2 to find out what this may mean for you.
K. Nepsa has a B.S. in Geology and a Master’s in GIS. She has lived in Arizona, HI, CA and Shanghai, China. Her hobbies include enjoying the outdoors via Jeep, Kayak, horse or foot. She has been a Vail resident since 2005.
