earth science study guide


Study Guide
Extracts from the Queensland Senior Earth Science Syllabus 2001
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7.1    Introduction to Earth Science

Overview

The study of the earth has captured the interest and imagination of people throughout the ages. The desire to experience and understand earth’s environments has pushed the frontiers of humankind’s exploration across the entire globe and beyond, to earth’s moon and to other planets. Astounding discoveries from space exploration have been matched in our knowledge of deep ocean environments and the interior of the earth. The driving force has been a deep human curiosity about our physical environment, coupled with a need to test hypotheses, to unravel earth’s history, and to gain insights into the formation of our solar system and the universe of which earth is just a small part.

Our earth represents a dynamic system in which the atmosphere, hydrosphere, lithosphere, and biosphere are constantly interacting and where natural cycles that involve water, rocks, and atmospheric gases play their part in supporting and sustaining life. Natural earth processes shape landscapes and maintain the planet’s environments by constantly reworking, conserving, and renewing its materials. The interaction of the atmosphere and hydrosphere strongly influences earth’s weather system and produces catastrophic events such as floods, cyclones, hurricanes and tornadoes. Hazardous earth processes such as earthquakes and volcanic eruptions, on the other hand, reflect internal earth processes.

Rock sequences confirm that hazardous events have characterised earth’s environments in past times. They also record an earth history involving even greater phenomena such as the opening of ocean basins and the formation of massive fold mountain chains. Major catastrophic events affecting earth’s global environment have influenced life forms significantly, for example, causing the extinction of the dinosaurs.

An understanding of our earth, its processes, and its geological history, is the key to an ecologically sustainable development of the planet’s resources. Only with this knowledge will humankind continue to derive the necessary benefits from the earth without jeopardising its environments. Although this knowledge also facilitates the choice of its safest environments for human habitation, history demonstrates that politics and economics largely dictate where communities settle and remain. Even when cities or towns are built in sites of high environmental risk, earth science plays an important role in allowing inhabitants to live with natural hazards. Technological advances have been made to improve the monitoring of the environment with the goal of minimising the impact of hazardous events. To predict exactly when and where catastrophic events will take place is not yet possible, however.

It is important to note that geological processes affect every living thing on earth. Some of these processes are very obvious and might be regarded as hazards. Others are not so obvious, but enable us to understand the evolution of the atmosphere, the emplacement of economic deposits of mineral resources, and the formation of productive and fertile soils and the sculpture of the landscape.

Humankind is dependent upon the earth for survival. An awareness of earth’s systems and how they affect, and are affected by, human activities, is fundamental to any study of earth science.

Subject matter and approach

One goal of this introductory unit is to establish the relevance of Earth Science to the lives of students. Its purpose is also to stimulate their interest in their natural surroundings and generate excitement for the subject by illustrating both the dramatic and the subtle natural phenomena that reflect Earth’s dynamic nature.

It is important to introduce students to the broad aspects of Earth Science. This should include illustrating the awesome yet delicate appearance of the ‘blue planet’ viewed from space, the magnificence of the rivers and forests, the wonders of the oceans, the tragedy and benefits of floods, the enormous strength of cyclones, the amazing spectacle of volcanic eruptions, the strength and power of earthquakes, and the importance of recycling our resources and taking care of our natural environment. It is crucial that the student appreciates that the earth is a highly dynamic planet, not only in terms of its hydrosphere and atmosphere but also in its land surface and interior.

Core areas of study

Suggested learning experiences

7.2 Our earth and its systems

Overview

Studies in earth science are best approached by considering the planet from the point of view of its various dynamic systems, the largest of which are the hydrosphere, lithosphere, atmosphere, and biosphere. Examples of smaller but equally dynamic systems include shoreline, glacial, volcanic, and fold mountain systems. Studies using this systems approach highlight the earth processes that operate across the wide range of earth’s environments. The flow of matter and energy between earth’s dynamic systems is conveniently illustrated in terms of a series of cycles. Of greatest importance are the energy cycle, the hydrologic cycle, the rock cycle and various biogeochemical cycles.

studies of the materials and their mineral constituents can provide an insight into the environments of their formation.

As far as is known, a unique combination of geological and astronomical processes has resulted in the development of a planet on which life can survive. The composition of the earth stands in great contrast with planets such as Jupiter and Saturn. The earth has a much lower percentage of light elements such as hydrogen and helium, and a much higher percentage of heavier elements such as iron, silicon, aluminium, and oxygen. The unique combination of composition, mass and position in space has determined many of the earth’s characteristics.

The earth we live on today is a result of interactions among the following factors:

As humanity continues to search to understand the earth, three of the most powerful or enduring ideas areuniformitarianism,catastrophism,andplate tectonics.These are important concepts in an environmental earth science course.

Hutton’s doctrine of uniformitarianism holds that the present is the key to the past. Ancient sandstones, for example, are interpreted as having started in much the same way as sand deposits today. On the other hand, much of what we have learned about the long history of the earth can be used to help us better understand the present and predict the future. Climate change models can be improved, for example, by incorporating knowledge of past climate change; and assessments of earthquake risk can be refined by drawing on previous behaviour as revealed by the geological record.

Catastrophism has waxed and waned in popularity among earth scientists. A central feature of geological paradigms up to the late eighteenth century, it was eclipsed by uniformitarianism in the nineteenth century and for most of the twentieth. In the late twentieth century, catastrophism has been invoked in events such as the extinction of dinosaurs.

The theory of plate tectonics has emerged as the most powerful geological idea of recent times. The predictive ability of this theory, together with its ability to draw together an enormous number of otherwise independent observations, has made it central to studies of the earth.

Subject matter and approach

Students should be familiar with the main concepts involved in a systems approach to studying the earth. Studies of the hydrologic, rock and energy cycles serve to interrelate the earth’s systems. Although earth processes of importance to each of the large systems should be studied, greatest attention should be placed on the lithosphere to support theoretical and practical studies of minerals and rocks.

Students should be familiar with the theory of plate tectonics. They should understand how the theory of plate tectonics describes the relationship between the features and the processes of the earth’s crust. At the same time, the students should also understand the nature of the interior of the earth.

Core areas of study

Suggested elective areas of study

Suggested learning experiences

7.3    Hazardous earth processes and materials

Overview

Earth processes that we refer to as ‘hazardous’ have existed throughout earth history. Even the most destructive events are part of the normal functioning of this dynamic planet; to a great extent, they make the planet habitable. Earthquakes and volcanic eruptions, for example, are among the processes that have formed the continents, shaped the landscape, influenced climatic zones, and allowed for the creation and stabilisation of the atmosphere and oceans. The action of wind and water causes flooding, landslides, and windstorms but also replenishes soil and sustains life.

Earth processes affect our lives daily in ways that are both subtle and conspicuous, beneficial and harmful. A knowledge of these processes and the hazards associated with them should play an integral role in the planning of human activities.

Earth hazards include earthquakes, volcanic eruptions, floods, and landslides. They are included in the broader concept of natural hazards, which encompasses processes or events such as locust infestations, wildfires, and tornadoes in addition to strictly geological hazards.

Some natural hazards are catastrophic events—occurrences that strike quickly but with devastating consequences. Other hazardous processes operate more slowly. Droughts, for instance, can last ten years or more. The socioeconomic impacts of extended drought are caused by the cumulative effects of season after season of below-average rainfall.

In general, natural processes are labelled ‘hazardous’ only when they present a threat to human life, health, or interests, whether directly or indirectly. In other words, we tend to take a human-centred approach to the study and management of natural and geologic hazards. This is human nature, of course; we are justifiably concerned with the protection of human life and property. But this approach has important implications, because it can lead to a style of hazard management in which geologic processes are cast as the ‘enemy’ and efforts made to manipulate the environment into submission. A somewhat different approach, which is currently receiving a lot of attention, focuses on improving scientific understanding of natural processes and their triggering mechanisms in order to provide a foundation for better management.

A different category of hazard, sometimes referred to as technological hazards, is associated with everyday exposure to naturally occurring hazardous substances such as radon, mercury, asbestos fibres, or coal dust, usually through some aspect of these substances in our built environment. Still other types of hazards arise from pollution and degradation of the natural environment, which have led to problems such as acid rain, contamination of surface and underground water bodies, depletion of the ozone layer, and global warming; we might refer to these as primarily human-generated hazards.

In order to incorporate knowledge about natural processes into the planning of human activities, we need to assess the hazards and risks associated with them. Ideally, scientific understanding can contribute to the establishment of an integrated system in which environmental earth scientists cooperate with government and private-sector decision makers to apply scientific and technical knowledge to the reduction of natural hazards.

Earth scientists have a particular responsibility to contribute to such efforts. Because so many natural disasters are associated with geological processes, earth scientists play an important role in furthering our understanding of hazardous earth processes, assessing the hazards and risks involved, accurately predicting hazardous events, and assisting in the prevention or the mitigation of impacts. All of these tasks depend on effective communication of scientific understanding about geologic processes.

Subject matter and approach

Students should become familiar with a range of hazardous earth processes and the effects of these on human life and property. Emphasis should be placed on the geological processes that cause each geohazard. At the same time, students should recognise that people’s actions may cause or increase the risk of earth hazards. The monitoring, prediction and potential control of geohazards should be considered. Studies of these processes should result in students coming to understand the relationship between plate tectonics and many earth hazards.

Students should be familiar with a range of hazardous materials and the effects of these on people’s lives. They should develop an understanding of the techniques developed to manage such materials.

Core areas of study

The nature, monitoring, and management of:

Suggested elective areas of study

Suggested learning experiences:

7.4    Earth’s resources and human impact on the environment

Overview

All organisms on this planet are entirely dependent on the earth for a supply of clean air, water, and food. Humans also actively use the earth’s natural resources as a source of raw materials for their own endeavours—manufacturing, housing, and transport. Any earth material that is necessary or valuable to humans therefore represents a resource. In this context, the range of earth’s resources is extensive. Air, water and soil are extremely important to our everyday existence; without any one of these resources, humankind would become extinct. Water also has important uses in industry. Various materials, rocks, and even fossil fuels such as oil are the raw materials used in the manufacture of almost every conceivable product—construction products, jewellery, electronics components, chemicals and even medicines.

Fossil fuels such as coal, oil and natural gas are vital sources of energy but, because fossil fuels are not renewable, alternative forms of energy are being sought. These include nuclear power, and solar and geothermal energy. We are also learning how to harness the energy of tidal action, windpower, and even biomass-derived energy extracted from alcohol and methane produced by the decay of organic material in landfill.

An understanding of the limited availability of earth resources has come with their escalating use. As a result, our use and management of such resources is now much more considered than it was previously.

Rehabilitation and sustainability are now integral components in the activity of extractive industries. In conjunction with this, the techniques used to find, extract and process resources have improved markedly, to such an extent that re-mining the tailings of ‘old’ mines has now become a significant part of the mining industry.

While we are reliant on earth resources, their extraction and use causes us to have a significant impact on the earth’s environment. Scientific endeavour is demonstrating the extent of this impact, from a historical, current and future perspective.

With an increasing understanding of the earth’s systems, scientists have identified evidence of human impact on the environment. Depletion of the ozone layer, the possible acceleration of the greenhouse effect, acid rain, thermal inversions, and decreasing air and water quality standards are commonly cited. It seems that these are the result of pollution and inadequate waste disposal. Unfortunately, any attempt to decrease pollution frequently increases the amount of waste requiring disposal.

In addition to the impact humans have on the atmosphere and hydrosphere, we also have an impact on the physical environment, often resulting in catastrophic events. Examples include flooding due to altered run-off patterns in cities, increased seismic activity under large dams, promotion of mass movement, and altered rates of erosion. The placement of all forms of constructions—dams, freeways, buildings, wells or even retaining walls—can have an effect on the physical environment.

In all cases, planning for the various forms of impact that humans have on the environment is essential. This may involve changing the way that we use the earth’s resources, developing new methods of waste disposal, and more careful studies of the ways human endeavour affects the environment.

Subject matter and approach

Students should become familiar with the range of earth resources and their use. Emphasis should be placed on the non-renewable nature of a large number of these resources. An understanding of the processes of formation of earth resources should be accompanied by an appreciation that humanity is using these resources at many times the rate of their formation. Students should understand the techniques involved in the exploration, extraction and processing of earth resources. It is important that they recognise the need for careful planning of mining processes due to the impact they can have on the local environment.

Students should also understand the impact that humans have on the environment. Sources of pollution, waste and other forms of environmental impact should be recognised, along with the techniques employed to control them. It is important that students are aware of the fragile state of the earth and the role that earth science plays in understanding and helping to reduce and minimise the impact humans have on our planet.

Core areas of study