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Competency 051: The Structure and Function of Earth Systems

Competency 051: The Structure and Function of Earth Systems

The teacher understands the structure and function of earth systems.

Earth Science describes the structure and composition of earth and how it has changed over time. It is crucial to many aspects of human life and the production of resources.

Why Earth Science?
The American Geological Institute describes the importance of Earth Science in this short video.

Subtopics:

The Structure and Processes of Earth

The beginning teacher understands the structure of Earth and analyzes constructive and destructive processes that produce geologic change.

Key Concepts:

  • Earth is composed of a geosphere (the rocks and molten core of earth) a hydrosphere (the water and ice in the oceans, air, lakes, rivers, and underground), an atmosphere (the various gases that form the air around earth), and a biosphere (living organisms on earth).
  • The geosphere is composed of a thin outer crust, a molten mantle high in silicon and magnesium, a semi-molten outer core high in nickel and iron, and a solid inner core.
  • Convection currents occur in the magma of the mantle. These currents push on the crust in different directions and produce the phenomena of tectonic plates. As the plates of the crust are pushed together or apart they produce many geologic features, like mountain ranges, ocean trenches, and volcanic islands.
  • Convection also occurs in the outer core and, due to its composition of conductive metals, magnetic fields and electric currents are produced. Besides making compasses functional, this magnetic field also protects the biosphere from charged particles emitted from the sun.
  • Erosion and weathering also produce geological features over time. Weathering is the breakdown of geologic material into smaller pieces. Erosion is the transport of material by water, wind or other means to another location.
  • Weathering can be categorized in two ways:
    • Physical (mechanical) weathering is the breaking down of rock and soil into smaller sections of the same kind of material. Water expanding as ice in crevices, wind grinding away the rock of a plateau, and water flow through a canyon all are examples of this type of weathering.
    • Chemical weathering occurs when materials react and form new molecular products that are soluble in water (dissolve in water). Caves are an example of this kind of weathering. Carbonic acid in seeping groundwater (H2CO3) reacts with calcium carbonate (CaCO3) in limestone, producing soluble calcium (Ca2+), which is carried away in the water. After long periods of time, underground tunnels are made through the eroded limestone rock.

Resources:

Earth Structure
Geography4Kids provides a good overview of the composition of Earlth and processes that have shaped our planet. Click on different sections, such as composition or magnetic field, to review specific topics.

Plate Boundaries
The Plate Tectonics website details the three types of tectonic plate collisions that occur on earth and the topography which results from them.

Geomagnetism
This FAQ on geomagnetism from the US Geological Survey explains how compasses work, the production of the magnetic field by the outer core, and how the Earth’s polarity changes over time (sometimes even reversing).

Mechanical and Chemical Weathering
John P. Stimac, Ph.D., of Eastern Illinois University discusses the ways that weathering occurs on rocks and how this can result in the formation of soils.

Erosion and Weathering
A wide variety of geological features caused by weathering are illustrated and explained in this photo gallery compiled by National Geographic.

Water Sources

The beginning teacher understands the form and function of underground and subsurface water.

Key Concepts:

  • Around 97% of water on Earth is saline (salty) and only about 1% of Earth’s water is in a form that practically can be used for human consumption and agriculture. The other 2% of Earth’s water mainly exists in polar ice caps and glaciers.
  • The water sources mainly used by humans for consumption and agriculture consist of the following.
    • Lakes, which can be formed by tectonic movements, glaciation, and erosion or sediment deposition (oxbow lakes). The chemical components of lakes, like salinity and nutrient concentrations, depend on their watersheds.
    • Groundwater, which seeps through pores in soils and rocks and accumulates in aquifers. Contamination and overuse are large problems related to this water source.
    • Rivers, which deposit sediment and minerals into oceans and lakes, sometimes creating agriculturally rich alluvial plains in the process. Rivers also are used for transportation as well as hydroelectric energy.
  • Oceans, by far the largest source of water on earth, are critical in affecting climates and provide food, minerals, and routes of transportation for the nations of the world.

Resources:

Where is Earth’s Water Located?
Graphical information about the distribution of water on earth is provided by the US Geological Survey.

Lakes
This description by Encyclopedia Britannica details many aspects of lakes. Lake formation and chemical composition should be the main focus of your review.

What is Ground Water?
The origins of ground water and the characteristics and sustainablity of aquifers are described by the US Geological Survey.

Physical Properties of Rivers
River currents, erosion, depostion, and estuary ecosytems are described and illustrated in this article from The Encyclopedia of Earth.

Ocean Resources
The tremendous importance of the world’s oceans is explained in this article from MarineBio. Key environmental concepts the article points out include fisheries management, oils spills, and the ocean as a climate buffer.

The Atmosphere

The beginning teacher applies knowledge of the composition and structure of the atmosphere and its properties.

Key Concepts:

  • The atmosphere is composed of a mixture of gases. The two most abundant gases are nitrogen (N2) and oxygen (O2), accounting for roughly 78% and 21% of the atmosphere, respectively.
  • The main greenhouse gases in the atmosphere are carbon dioxide (CO2) and methane (CH4). Greenhouse gases reflect infrared radiation (heat) back towards the surface of the earth, insulating the planet.
  • There are four layers of the atmosphere, each with different ranges of temperature, pressure, and chemical composition. The stratosphere contains the ozone layer, which is vital in blocking hazardous ultraviolet radiation.
  • The atmosphere functions as a medium by which weather and the water cycle occur. Convection currents in the atmosphere produce wind, which can be harnessed as an energy source. Also, useful substances like nitrogen, helium, argon, and radon can be extracted from the atmosphere through a process similar to distillation.

Resources:

Earth’s Atmosphere
Learn about the gaseous composition of the atmosphere and the characteristics of the troposphere, stratosphere, mesosphere, and thermosphere, as explained by Anne E. Egger, Visionlearning.

Interactions between Spheres

The beginning teacher demonstrates and understanding of the interactions that occur among the biosphere, geosphere, hydrosphere, and atmosphere.

Key Concepts:

  • The main ways in which the geosphere, hydrosphere, atmosphere, and biosphere interact are through the nutrient, water, and rock cycles. These interactions are discussed in detail in competency 52.
  • Other interactions are described below.
    • The course of evolution and the diversity of life have been affected by changes in the geosphere. These changes include movement of continents and geologic formations that isolate geographic areas and habitats.
    • The magnetic field produced by the outer core protects the atmosphere and biosphere from solar winds. Also, certain animals use the Earth’s magnetic field to navigate.
    • The ozone layer in the atmosphere helps prevent harmful ultraviolet waves from reaching the ecosystems of the world.
    • Plant roots, fungal hyphae (filaments), and bacteria prevent erosion by binding together soil particles or by trapping soil within a network of fibrous or filamentous materials.

Resources:

Marsupials
A great example of how the geosphere has affected life on earth was the migration, isolation, and evolution of marsupials in Australia. The first link shows a video of how marsupials became isolated in Australia by continental drift. The second link describes how marsupial evolution in Australia mimicked placental mammal evolution elsewhere in the world after the dinosaur extinction 65 million years ago.

  1. The Evolution of Marsupials by the Science Channel.
  2. The Marsupial-Placental Convergence from Dr. Johnson’s Backgrounders.

Polar Substorms
NASA explains how Earth’s magnetosphere protects earth from solar ionic discharges. However, the magnetic field does not always protect the atmosphere near the Earth’s poles and this produces the “aurora” phenomenon.

Ozone Basics
The National Oceanic and Atmospheric Administration tells the basics about the ozone layer, its function, and how it can be depleted.

Changes in Earth Systems

The beginning teacher applies knowledge of how human activity and natural processes, both gradual and catastrophic, can alter earth systems.

Key Concepts:

  • Cycles of warming and cooling have occurred throughout Earth’s history, as evidenced by polar ice core samples and oxygen isotope ratios in calcium carbonate deposits. It is the main consensus of the scientific community that these cycles produced the ice ages and are related to greenhouse gas accumulation and the long term Milankovich astronomical cycles (which occur over thousands of years).
  • In the last 100 years, humans have released CO2 and other greenhouse gases into the atmosphere at an alarming rate (deviating greatly from the normal cycles) by burning fossil fuels. The scientific community attributes this human activity to the recent increases in global temperatures, the rate of polar ice melting, and changes to Earth’s regional climates.
  • Volcanoes and asteroid/comet collisions also can affect global climates as dust and chemicals released by them can block solar radiation, cooling the planet.
  • Acid rain is produced when water vapor reacts with SO2, CO2, and nitrogen oxides (all produced by the combustion of fossil fuels) to form acids. Acid can then build up in soils and bodies of water, affecting ecosystems in the process.

Resources:

The Global Carbon Cycle
This presentation by Nancy Moreno, Ph.D., on the atmosphere, carbon cycle, and the greenhouse effect provides a nice introduction on the topic of climate change.

Global Climate Change
NASA provides a more detailed analysis on the evidence and causes of climate change and effect that this will have on Earth’s systems, on the following three pages: evidence, causes, effects.

Climate Effects of Volcanic Eruptions
Learn how volcanoes can effect the atmosphere and climate, and provides examples of such events occurring throughout history, from San Diego State University.

Coal Combustion and Acid Rain
This video from Britannica summarizes the causes of acid rain, and the ways that this outcome from burning coal can be reduced.

Earth’s Energy Sources

The beginning teacher identifies the sources of energy (e.g., solar, geothermal) in earth systems and describes mechanisms of energy transfer (e.g., convection, radiation).

Key Concepts:

  • Solar energy is the main driver of change in the hydrosphere, biosphere, and atmosphere. Examples of this include the water cycle, ocean currents, energy flow through ecosystems, and the greenhouse effect.
  • Geothermal and radioactive decay provide the energy driving geosphere changes, such as volcanoes, crust movement, and the transformation of some rocks.
  • Solar energy is absorbed and reflected from Earth as radiation. If absorbed by the hydrosphere or atmosphere, convection in water and air can create ocean currents and wind. Geothermal energy is mainly transported through the earth systems by convection and conduction.
  • Tides are created by Earth/Moon/Sun gravity effects on one side of the Earth balanced by centrifugal acceleration of the earth’s water on the other side of the planet. This creates two “bulges” of water on opposite sides of the Eart, which correspond to the high tides, and non bulging areas, which are at low tides.

Resources:

Global Energy Balance
This animation from Scripps Institution of Oceanography shows the sun’s energy being absorbed, reflected, and re-radiated back out in a variety of different ways to create an energy balance. The premise of the greenhouse effect is that greenhouse gases offset this balance, causing the earth to absorb more energy than it emits.

Understanding Convection Currents
Paul A. Heckert explains the nature of convection currents and gives three examples of them in Earth’s systems: the mantle moving tectonic plates, wind patterns, and ocean currents.

What Causes the Tides?
Click the image to start this animation, from PBS, which illustrates how tides occur on earth with respect to the moon. However, it is important to note that the sun is not included in this animation. When the gravitational pull of the moon and sun align, stronger tides are produced. As many anglers may note, this is why tides are highest during full and new moons.



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