Plate Tectonics and the Scientific Method
Plate Tectonics
Plate Tectonics: Moving and Shaking. There are many major plates and dozens of smaller, or minor, plates. Six of the major plates are named for the continents within them, such as the North American, African, and Antarctic plates. Smaller plates are important to shaping the Earth too. The tiny Juan de Fuca plate is largely responsible for the volcanoes that dot the Pacific Northwest of the United States.
The plates make up Earth’s outer shell, called the lithosphere (includes the crust and uppermost part of the mantle). Churning currents in the molten rocks below propel them along like a jumble of conveyor belts in disrepair. Most geologic activity stems from the interplay where the plates meet or divide.
Types of Tectonic Boundaries
Convergent: where plates move into one another; divergent: where the plates move apart; and transform: where the plates move sideways in relation to each other.
Convergent Boundaries
Where plates bearing landmasses collide, the crust crumples and buckles into mountain ranges. India and Asia collided about 55 million years ago, forming the Himalayas. These boundaries occur where a plate of ocean dives, in a process called subduction, under a landmass. As the overlying plate lifts up, it forms mountain ranges. The diving plate melts and is often spewed out in volcanic eruptions (e.g., mountains in the Andes).
At ocean-ocean convergences, one plate usually dives beneath the other, forming deep trenches like the Mariana Trench.
Divergent Boundaries
Magma from deep in the Earth’s mantle rises toward the surface and pushes apart two or more plates. Mountains and volcanoes rise along the seam. The process renews the ocean floor and widens the giant basins. A single mid-ocean ridge system connects the world’s oceans, making the ridge the longest mountain range in the world. Example: Great Rift Valley in Africa. If these plates continue to diverge, millions of years from now, eastern Africa will split from the continent to form a new landmass.
Transform Boundaries
Where two plates grind past each other along what are called strike-slip faults. These boundaries don’t produce features like mountains or oceans, but the halting motion often triggers large earthquakes. Example: San Andreas Fault in California.
Layers of the Earth
(De arriba a abajo): Crust, Lithosphere, Mantle, Outer Core, Inner Core.
The Scientific Method
It’s a process that is used to find answers to questions about the world around us. There are some versions that have more steps. They all begin with the identification of a problem or a question to be answered based on observations of the world around us and provide an organized method for conducting and analyzing an experiment.
Phases of the Scientific Method
- Identify the problem: You find a problem and write questions that address the problem or topic you want to investigate.
- Form a hypothesis: It’s an educated guess based on observations and your knowledge of the topic.
- Create an experiment: Develop a procedure for a reliable experiment and address safety rules.
- Perform an experiment: Follow the steps in your procedure to perform it.
- Analyze the data: It’s information gathered during an experiment. If your data is inaccurate, you have to modify the experiment and rewrite your procedure to address the flaws in the original experiment. If it is verified, you have to communicate the results.
Key Terms
- Control: Part of an experiment that is not being tested and is used for comparison.
- Procedure: Describes the steps you use during an experiment.
- Conclusion: Summarizes an experiment and its results.
- Independent variable: Part of the experiment that is being tested or the part that is changed by the person doing the experiment.
- Dependent variable: Part of the experiment that is affected by the independent variable.