In this part of the unit, the students will be applying what they have learned about matter in motion to the natural world. Children will get a brief glimpse of different natural disasters and occurrences through shared reading, and will be allowed to choose one to research further and report on. This part of the unit will be highly differentiated for the varied abilities and interests in your class. Each student will be working at his or her own level on a topic of his or her own choosing.
In the section titled Student Resource List, is a list of quality children’s literature and other resources to pique students’ interest in such topics as rain storms, hurricanes, tornadoes, earthquakes, and the water cycle. Each day during reading time, the teacher should spend 15-20 minutes highlighting a specific natural phenomenon. In the section below there is content area knowledge for teachers regarding few common occurrences that may be of interest to students.
This part of the unit is an excellent opportunity to teach the children how to strategically read nonfiction texts. Nonfiction is different from fiction and must be approached differently. Start by reviewing the differences between fiction and nonfiction. This can be done by working together as a class and using a Venn diagram to highlight the similarities and differences. (Miller, 2002) Teach the children to pre-read by using the table of contents, headings, photographs, and diagrams to make predictions about what they will learn and to ask questions to set a purpose for reading. (See questioning lesson for more information)
Content Knowledge for Teachers
The Hydrologic Cycle
The hydrologic cycle is the system through which our planet’s water is circulated. This is an excellent natural example of state changes of matter that children can research and see first hand examples in their own backyards. The driving force behind the water cycle is the sun’s heat. As the sun heats the earth, the temperatures of large bodies of water begin to rise. As the temperature increases some of the water escapes as vapor through evaporation. The water vapor is less dense than the air and rises up through convection and upwelling warm air currents. The vapor rises until it reaches a point in the atmosphere at which it can cool and condense. Through condensation, the water returns to the liquid form as small droplets. When the droplets form groupings large enough to see, clouds are formed. Eventually, the droplets become too heavy to be supported, precipitation falls, and the cycle continues. The hydrologic cycle also includes erosion, flooding, and the reshaping of the earth’s landscape.
Air masses with different temperatures and moisture contents are separated by fronts. A front is “A sloping surface separating air masses.” (Abbott, 2004) When a cold front moves in, the cold dense air traveling along the earth’s surface wedges warmer air up into the atmosphere. As the quickly rising warm air cools it forms clouds; however, as the air rises, it remains warmer and less dense than the surrounding air making the whole system unstable. (USA Today, 2008) As more and more warm moist air rises in a storm system, electrical charges build inside the clouds. Particles with opposite charges are collected on the ground, and as the charges build, the attraction grows stronger and despite the air’s tendency to resist electrical flow, the charges eventually come towards each other completing the electrical circuit when they connect. It is then that the charge from the ground flashes upwards. This is the flash we see in a storm. (USA Today, 2008)
There are three different types of earthquakes: subduction zone earthquakes, transform fault earthquakes, and spreading center earthquakes. (Abbott, 2004) All three types of earthquakes are caused by tectonic crustal plate movement. An earthquake is an example of what happens to matter when it is acted upon by an outside force: the pressure built up by mantle convection and crustal movement.
The world’s largest earthquakes are subduction zone earthquakes. These earthquakes occur when one crustal plate becomes cold and dense and begins to sink underneath another plate into the mantle because of convection. Stress is built up as the slowly sinking plate pushes back down towards the mantle. Eventually, the overriding plate snaps because of the pressure. The quakes cause deformation, and breaking of the crust. (Abbott, 2004)
Spreading center earthquakes happen in places where two plates are moving away from one another. These earthquakes are smaller and more frequent than subduction zone earthquakes. Because the hot rock in these spreading centers do not support stress well. (Abbott, 2004)
San Francisco’s earthquakes are due to its location atop a transform fault. Transform faults move past each other in opposite directions. Friction between the two plates builds up stress. Some of the stress is released when the plates shift and cause earthquakes. (Abbott, 2004)
The earth below our feet is constantly moving and changing. The interior of the earth is made up of layers: the crust, the mantle, and the core. The earth’s surface is constantly cooling to space. The hot viscous mantle convects, and mantle rising near the surface can melt and produce magma. The pressure builds beneath the earth’s surface until the cold brittle crust begins to crack, sometimes causing small volcanic related earthquakes. (Abbott, 2004) When the pressure is too much to be contained by the crust, a volcano explodes with a force that is directly proportionate to the amount of pressure that has built up.
Proportionally smaller amounts of pressure will cause slow flowing lava exemplified in the volcanic activity in Hawaii. In this type of eruption, the pressure is often being released, and consequentially does not have time to build up enough to cause an explosive event. Because of the low viscosity of the basalt magma water is easily able to escape in the form of a gas: steam. The matter being emitted from the volcano is in a liquid state and flows out onto the ocean floor, or land mass surrounding it, where it cools and becomes solid. (Abbott, 2004)
Large amounts of pressure cause explosive volcanoes similar to the Mt. Vesuvius eruptions. In these volcanic eruptions the pressure builds up over a long period of time and when the crust above can no longer support the pressure, it blows its top. These volcanoes are also so explosive because of the high viscosity of the matter being emitted. The rhyolitic magma is less fluid than the more common basalt magma, and the result is gas that has a more difficult time escaping. When the gasses can not escape, they expand in volume and then explode. The matter in these types of explosions is present in the form of highly viscous liquid magma, exploding gasses escaping from the magma, and solid rock that is often broken from the crust in the violent explosion. (Abbott, 2004)