Earthguide - Demo

California standards
Summary from Science Framework

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The earth sciences use concepts, principles, and theories from the physical sciences and mathematics and often draw on facts and information from the biological sciences. To understand Earth's magnetic field and magnetic patterns of the sea floor, students will need to recall, or in some cases learn, the basics of magnetism. To understand circulation in the atmosphere, hydrosphere, and lithosphere, students should know about convection, density and buoyancy, and the Coriolis effect. Earthquake epicenters are located by using geometry. To understand the formation of igneous and sedimentary minerals, students must master concepts related to crystallization and solution chemistry.

Because students in grades nine through twelve may take earth science before they study chemistry or physics, some background information from the physical sciences needs to be introduced in sufficient detail. From standards presented earlier, students should know about plate tectonics as a driving force that shapes Earth's surface. They should know that evidence supporting plate tectonics includes the shape of the continents, the global distribution of fossils and rock types, and the location of earthquakes and volcanoes. They should also understand that plates float on a hot, though mostly solid, slowly convecting mantle. They should be familiar with basic characteristics of volcanoes and earthquakes and the resulting changes in features of Earth's surface from volcanic and earthquake activity.

excerpt from:
Chapter Five: Earth Science, Investigation and Experimentation.
Science Framework for California Public Schools: Kindergarten Through Grade Twelve, 2004.
California Department of Education.

Acquired from online source on July 13, 2007.

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Relevance

Knowledge of tectonic processes can help save lives and property. Plate tectonic processes control where, when, and how often geologic hazards such as earthquakes, volcanoes and tsunami might strike, and their magnitude.

Knowledge of the Earth's tectonic history helps to locate some types of natural resources, such as petroleum and minerals, that were formed in environmental settings associated with plate configurations that no longer exist and have since moved around.

Knowledge of tectonic settings allows us to understand differences in the present-day distribution of natural resources such as soil types, unique geologic features, water supply, and much more, all around the world today. These are the resources that would have limited life within regions in the absence of import processes.

Knowledge about the specific tectonic history of the Earth gives us a panoranimc view of environmental change and the succession of life over time. It allows us to consider how environment and life influence each other over planetary scales of time and space.

Knowledge of tectonic processes and its causes allows us to understand our own planet in the developing context of understanding all rocky planets, whether in our own solar system or beyond.

Overview

The familiar arrangement of land to ocean, and location of mountain ranges is unique to our time. It was radically different in the past. Not long ago in a geologist's way of thinking, India was once located close to Antarctica and there was no Atlantic Ocean. Earth continually reshapes its surface by the processes of plate tectonics. The subject of plate tectonics includes the processes the shape the Earth's surface, the mechanisms that drive these processes, the resulting surface features and the reconstruction of past global geographies.

The overarching concept of plate tectonics explains the presence and pattern of Earth's most significant surface features - including its oceans, land and mountains - today and in the past. The historical development of this revolutionary concept over the last century illustrates how human understanding of the natural world, i.e. natural science, progresses.

The term "tectonics" refers to planetary processes that shape and deform planets, particularly their large-scale surface features such as formation of volcanoes, non-volcanic mountains, faults and folds. Since tectonic processes on Earth are characterized by the motion and resizing of eggshell-like units at its surface called "plates", this style of tectonics is called plate tectonics. Other rocky planets in our solar system may be/have been tectonically active, but none seem to exhibit evidence of plate tectonics

The motion of tectonic plates and the slow convective motion of rock inside the Earth are driven by the same energy source inside the Earth, the heat trapped inside the Earth long ago. But plate motion isn't directly related to convective motion. The plates are not dragged along the Earth surface by the convective motion of slowly churning cells of underlying rock. The complex relationship between convection and plate motion is not well understood.

The key processes of plate tectonics on Earth, seafloor spreading and subduction, take place where rock moves upward and downward, respectively. These processes are primarily associated with significant features of the seafloor: Sea floor spreading forms and takes place under midocean ridges and subduction occurs at trenches.

Sometime long into the future, the Earth's interior will become too cool to support tectonic activity. Until that happens, tectonic processses will work against the wearing effects of erosion and continue to reshape the surface of the planet, maintaining the most distinctive features of the Earth such as its highest mountain ranges and deepest canyons.

Note: Everything here is preliminary.
Please feel free to use it, but consider it a draft, i.e. not ready for release. :)

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Original resources

Definition of tectonics and plate tectonics
How the concept of continental drift evolved into plate tectonics; and why the concept of plate tectonic is an improvement over continental drift
Students tend to revert to the concept of continental drift, rather than plate tectonics, as the basis of their core understanding of solid Earth processes.
Three kinds of plate margins
The edges of plates vs. edges of continents — So simple to define, but difficult for students to distinguish in practice.
Two kinds of continental margins
What plate tectonics has to do with mountain-building
Two ways of defining the internal layers of the Earth
These are two different ways of divvying up the same thing, like arranging ...
Seafloor features and how they are related to the places where key tectonic processes take place at the edges (margins) of plates
Note: The concepts of continental drift and plate tectonics concepts may not be clearly distinguished.
Standard 3a: Students know features of the ocean floor (magnetic patterns, age, and sea-floor topography) provide evidence of plate tectonics.
How we know that plates move - direct evidence
Note: Although most explanations concentrate on the logic, development and acceptance of the plate tectonic concept over time, acceptance of plate tectonic activity and its potential consequences no longer depends on this understanding to some extent. Modern technologies let us observe the plates actually moving.
How we know that plates move - circumstantial evidence
Note: Until recently, there was little or no direct evidence that plates move. However, plate tectonic activity was accepted because it accounted for many otherwise unexplained observations. Acceptance of the theory was a little like making making a court decision - a preponderance of multiple and consistent circumstantial evidence made a strong enough case to sway the jury to accept plate tectonics. There was not a better alternative.
Note: Since the discovery of the striped magnetization pattern of the seafloor, acceptance of plate tectonics moved forward because that pattern was very difficult to explain otherwise. Important as it is, it is difficult for many students to understand why it is such a compelling piece of evidence.

Evidence from the seafloor:
Note: Evidence from the seafloor, rather than land, is more illuminating. However, that evidence is limited to the past 200 million years of the Earth's tectonic history.
Evidence from the land:
Evidence from both land and sea:

Prerequisites: Earth science

The interior of the Earth
Magnetic field
How rocks are dated
Earthquakes
Volcanoes
Midocean ridges
• Longest topographic features on Earth.
• All seafloor created at the midocean ridges.
• Shallowest major features in the ocean other than transition to land.
• Not all midocean ridges are located in the "middle" of the ocean.
• Not all midocean ridges exhibit rift valleys along their axis.
Subduction zones
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Other sciences
Math

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