Terrifying tremors, swaying of lights, the rumbling sound during an earthquake, can cause any person to be in complete awe of the Earth's powers. The steaming, hot magma, oozing down the sides of an erupting volcano, reveals another mystical power expressed by our Earth. Fear led ancient people to create myths to explain these events. Modern people usually just live with the danger, without really knowing what is happening to the earth.
Scientifically, it was very difficult for geologists prior to the mid 1900's to explain what was happening to the Earth. It wasn't until sophisticated geophysical equipment was developed that scientists began to unlock the mysteries of the Earth. There were clues, but it was not until the 1960's that geologists began to put the pieces of the puzzle together to formulate the plate tectonic theory was a new working model. Active research in seismology, tectonophysics, geophysics, and engineering may someday provide information that will help predict and possibly control this movement. Because new data may change the current philosophy, one who teaches about plate tectonics must make students understand that this is an evolving, dynamic subject. Solutions for today's hazards might also change as we learn more and more about how our Earth releases stress.
The Plate Tectonic Cycle refers to the movement of large portions of the earth's crust in what is termed "plates." The boundaries of these plates are generally defined by the occurrence of volcanoes and earthquakes. The driving forces that move these plates are a combination of events that occur within the Earth. Stresses on the crust caused by the spinning of the Earth also is a factor. The immediate fueling of the movement probably occurs within the atmosphere which includes the crust of the earth and the upper portion of the mantle. There are basically 2 divisions that geologist use to divide the earth - one that deals with the entire Earth (core, mantle, and crust) and one that deals with the outer portion (asthenosphere, lithosphere, hydrosphere and atmosphere) (figure 1). More information is known about the asthenosphere and the lithosphere because data is more easily obtained. The mechanism of how these various layers of the earth interact is still being investigated.
Children are fascinated with the spectacular
volcanic eruptions that occur throughout the world. Volcanoes are very
important for interpreting what is occurring within the outer portion of
the Earth. In addition, as the new Earth developed 4.5 billions years
ago, volcanoes released steam, which later became one of the major
sources of water on this planet. Volcanoes produce volcanic rocks
(igneous rocks) that have built the surface of the Earth. In the theory
of Plate Tectonics, most volcanoes are produced where two lithospheric
plates (the outer skin of the earth) either diverge (move away from each
other) or converge (come together, usually with subduction). In the
lower primary grades, recognizing the various shapes that volcanoes make
and learning that volcanoes produce igneous rocks should be emphasized.
In the upper primary grades, learning where volcanoes are and plotting
them on a map will help students understand how volcanoes unravel clues
about how the Earth moves.
Students discover that volcanoes produce rocks and that all mountains are not volcanoes. Volcanoes have many different shapes, which are created by various styles of eruption. Molten lava is a viscous fluid that cools to produce different types of rocks. Students will learn how to recognize the different types of eruptions by looking at different rocks. Students will compare and contrast magma and lava, as well as looking at different types of eruptions.
11. UPPER PRIMARY - VOLCANOES PROVIDE DATA
Students compare three different types of volcanoes: shield, composite, and cinder. They analyze and evaluate how volcanoes can help scientists understand plate tectonics. Students will evaluate the different volcanic rocks with respect to their rates of cooling, type of eruption, and original chemical composition. Students compare why volcanoes occur at diverging and converging plate boundaries.
Understanding earthquakes teaches students about the inside of the Earth and what causes movement on the surface of the Earth. Students first must understand that stress within the crust of the Earth can "relieve" itself by giving off energy (earthquakes) through seismic waves, The transmission of theses waves can cause minor to major damage to structures on the surface of the Earth, depending on the intensity of the original stress and its mitigation through the crust. Students will see where earthquakes occur on the Earth’s surface, try to determine why earthquakes occur, and relate earthquake occurrence to plate tectonics.
I. LOWER PRIMARY - EARTHQUAKES RELEASE ENERGY
Students learn that earthquakes are a mechanism in which the surface of the Earth relieves itself of stress. They evaluate the strength of an earthquake by testing different earthquakes on a primary shaker table. Students analyze how energy is released through different substances and relate that energy to energy released by an earthquake. Students compare the different types of damage caused by earthquakes. Faults caused by crustal movement in the local area are also explored.
II. UPPER PRIMARY - EARTHQUAKE WAVES PROVIDE DATA TO INTERPRET THEEARTH’S INTERIOR
Students learn about the different ways in which scientists describe the movement during an earthquake. They learn that the Richter Scale mathematically measures the intensity of ground shaking and that the Modified Mercalli Scale measures how people feel the intensity. Students will compare the different types of waves generated by an earthquake. They learn to distinguish a P (primary) and S (secondary) wave, and to describe the movements of the waves. P-waves represent a push-pull movement, while S-waves are shearing waves. Students analyze how different substances transmit seismic waves differently, and learn how to interpret these waves. They learn that scientists use them to understand what is inside the Earth.
Plate tectonics is a fancy way of explaining how
and why the outer part (the crust and upper mantle) of the Earth has
moved through time. The continents and oceans that we recognize today
have not always been the same size, nor have the always been in the same
locations. They have shifted and moved since the inception of continents
and oceans. This unit focuses on how earthquakes and volcanoes provide
data for understanding plate tectonics. Geologists also have structural,
paleontological, and geophysical evidence that confirms plate tectonics.
Students learn that the outside of the Earth is
made up of continental and oceanic crust. They learn to distinguish
continents and oceans, and how the relate to plate boundaries. They
determine that stress in the Earth’s crust causes earthquakes, and is
caused by plate motion. The students analyze how this movement occurs.
The students also learn that the Earth is made up of plates, and that
certain substances react differently to stress.
Students will discover that the edges of plates are defined by the locations of active volcanoes and earthquakes. They learn that plates can meet by either converging (coming together), diverging (parting), or slipping past each other. Topics to be discussed include how compression in the crust builds mountains and how plate boundaries are defined. Students interpret why earthquakes and volcanoes define plate boundaries, and look at different theories that can explain crustal movement. Students distinguish that plates are composed of the crust and upper mantle (collectively called the lithosphere), and that plates move over the asthenosphere.
Natural disasters have occurred throughout time. Catastrophes caused by volcanoes and earthquakes are not only spectacular, but can also be devastating if they occur in populated areas. This unit describes the hazards produced by volcanoes and earthquakes. Students begin to learn that these hazards are natural and are important in keeping the Earth internally "happy". If a student experiences such and event, these units also prepare students to act sensibly. Students learn about past damage to see that "Mother Nature" is not a force that can be tamed. Humans must understand the hazards that volcanoes and earthquakes cause in order to avoid their dangers.
I. LOWER PRIMARY - EARTHQUAKES AND VOLCANOES CAN CAUSE DAMAGE
Students discover that earthquakes and volcanoes can cause damage to property, people, and other organisms. They learn how to use their crucial thinking skills in order to avoid danger. The students analyze damage caused by both earthquakes and volcanoes. Students learn how earthquakes cause damage due to shaking, and how to evaluate what to do during an earthquake. The evaluate dangers both at home and at school.
II. UPPER PRIMARY - STRUCTURAL DAMAGE CAUSED BY EARTHQUAKES AND VOLCANOES
Students learn how the intensity of an earthquake causes damage. They will learn how to design internal areas that resist shaking during an earthquake. The students interpret why some volcanoes are more dangerous than others. Students also analyze how earthquakes and volcanoes are associated. The students will also engineer structures that are safe during an earthquake.
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