1.3 Environmental Geology

Steve Earle

Earth System Science is an important part of Environmental Geology, and so interaction between systems is considered in almost every topic covered in this textbook. But Environmental Geology is about much more than Earth System interactions.

Environmental Geology is about the interface between geological processes and the environment, and we can choose to use a broad definition of “the environment”. In this textbook that covers all types of Earth Systems, including systems involving the biosphere (or ecosystems if you like); systems of the hydrosphere and atmosphere, such as the hydrological cycle and glaciation; and systems of the geosphere, such as volcanism, earthquakes and slope failure. But it also includes human activities that have implications for the geosphere (and hence the rest of the Earth System), such as mining, energy resource extraction, and waste disposal: into the ground, into water and into the air.
The major topics considered here (apart from a review of Physical Geology in Chapter 2) are as follows:

Chapter 3: Geological Control Over the Earth’s Climate. Climate change is the most significant issue of our time, and in order to understand how we are changing the climate now we need to know how it has changed naturally in the past. We will look back in time to consider the geological and other processes that have controlled our climate over the past 4.6 billion years. These include long-term changes in the sun, evolution of living organisms, continental positions, mountain building, changes to ocean currents, volcanic eruptions, variations in the Earth’s orbital shape and tilt and collisions with extra-terrestrial objects.

Chapter 4: Glaciation. Glaciation has significant implications for topography and surficial materials and the extent, motion and melting of glaciers are important aspects of the Earth System. In this chapter we will consider some of the Earth’s past glacial periods, the persistent cooling over the Cenozoic, and the cyclical controlling factors of the Quaternary glaciations. We will compare continental and alpine glaciation and will examine glacial erosion landforms and glacial deposits and their implications for other aspects of Environmental Geology.

Chapter 5: Slope Failure. Plate motions and volcanism create steep slopes and those slopes are subject to the pull of gravity. In looking at slope failure we will consider forces on slopes, the natural angle of repose of loose materials, the importance of water, types of failure motion, classification of slope failure, the implications of glaciation for slope failure, triggers for slope failure, and implications of climate change for slope failure.

Chapter 6: Earthquakes. Earthquakes cause massive destruction and death around the world and it is important to understand them so that we can all take steps to reduce our vulnerability. We will consider plate boundary processes, rock strength, elastic deformation, sticking and slipping, rupture surfaces, seismic waves, amplification, liquefaction, earthquake predictions and warnings, and public and personal earthquake preparation.

Chapter 7: Volcanoes. As noted above, volcanic eruptions are an important component of the Earth System, but they also represent significant geological hazards. We will look at volcanism in the context of plate boundary processes, the importance of magma characteristics, volcanic hazards (lava flows, pyroclastic flows, lahars, ash fall), benefits from volcanism, predicting eruptions, and preparing for potential eruptions.

Chapter 8: Resources. Our civilization is built around a supply of metals, so it is important to understand where they come from and the implications of their extraction and use. We will consider background metal contents in rocks and metal enrichment processes, alteration of surrounding rock, mining methods, mine wastes, ore processing wastes, acid rock drainage and metal contamination, mine-waste accidents, and the effects of use of metals on climate change. We will also take a look the sources and environmental issues related to some of the metals important to modern technology, including lithium for batteries.

Chapter 9: Energy Resources. Our current way of life is tied to an abundant supply of cheap energy, and for the past 200 years that has been provided mostly by fossil fuels. As we know, that cannot continue, so we must shift our focus to sustainable energy sources. In this chapter we will look at the formation, extraction, use and emissions of coal, oil and gas. We will also consider other energy sources such as: uranium, hydro, wind, solar, geothermal, and wave energy.

Chapter 10: Soils and Clay Minerals. Eight billion people cannot live on this planet unless we grow a lot of food, so an understanding of soil is critically important. We will discuss some of the variables in soil formation, such as climate, parent material, slope and time, and also the importance of soil conservation. Clay minerals are important components of soils, but they are also significant to many other geological processes. We will consider the origins, mineralogy, properties, importance of clay minerals in the context of agriculture, climate change, earthquakes, mineral exploration, groundwater, slope failure, waste disposal, and environmental geochemistry.

Chapter 11: Water. A supply of clean water is essential to our lives, and in many areas that comes from surface sources like rivers and lakes. We will discuss the basics of hydrology, hydrographs, flood recurrence intervals, dyking, dams, and flooding, along with natural and anthropogenic contamination, and implications of climate change for surface resources.
The other major water source is groundwater, and there are many ways in which surface water and groundwater are connected. In order to understand groundwater resources, we need to examine porosity and permeability, aquifers (unconfined and confined), the water table and the potentiometric surface, and hydraulic gradient. Some other issues of importance are wells and pumping, groundwater chemistry, contamination, and the implications of climate change.

Chapter 12: Karst and Caves. Caves typically develop in areas with soluble bedrock, such as limestone. They can have significant environmental implications. We’ll be looking at the surface and underground features of cave landscape, how water flows through caves, how caves form, some of the contents of cave systems, and how humans interact with caves and karst.

Chapter 13: Flooding. In terms of human and economic cost, flooding is the serious type of natural disaster, and as we have seen in recent years, it is only going to get more frequent and more serious with climate change.  In this chapter we will discuss the causes and consequences of flooding, and some of the steps that can be taken to reduce the impacts of flooding.

Chapter 14: Waste Disposal. Solid waste disposal is a geological problem because most of our waste is still placed in holes in the ground. We will discuss the sources and composition of waste, waste diversion, the components of a landfill, the generation and composition of leachate solutions, and landfill gases and their contribution to climate change.

Chapter 15: Consequences of Climate Change. Chapter 3 is about some of the natural processes of climate change that have taken place over Earth’s history. In Chapter 15 we’ll focus on anthropogenic climate change and some of the serious consequences we are currently seeing, and can expect to see more of in the future, including glacial ice melt, sea-ice melt, destabilization of permafrost, extreme drought and rainfall, wildfire, sea-level rise, tropical storms, changes to ocean currents, ocean acidification, and how those changes can affect geological processes.

It isn’t difficult to see that Environmental Geology is more important now than it has ever been. This is partly because environmental issues in general are more important than ever due to the crisis of climate change and the rapidly expanding human population, but also because climate change is, to a large degree, a geological problem. We can understand its past by studying the geological record going back thousands, millions and billions of years and we can understand its present by applying geological methods to data collection and analysis. Moreover, climate change is affecting many processes that fall into the realm of Environmental Geology, such as water supply, flooding, erosion, deglaciation, and slope failure.
Most important of all, we can affect the future of climate change by changing the way we do things, and every one of us has a role in making those changes.


1.3 Environmental Geology Copyright © by Steve Earle. All Rights Reserved.

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