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Course: Middle school Earth and space science > Unit 4
Lesson 3: Plate tectonicsIntroduction to plate tectonics
Google ClassroomReview your understanding of plate tectonics in this free article aligned to NGSS standards.
Key points:
- Earth’s lithosphere, or outermost shell, is broken up into large pieces called tectonic plates.
- These plates move slowly over the asthenosphere, a layer of softer rock below the lithosphere. On average, tectonic plates move a few centimeters per year.
- The place where two plates meet is called a plate boundary. There are three main types of plate boundaries.
- Divergent boundaries occur where two plates are moving away from each other. Along these boundaries, rift valleys and mid-ocean ridges are common.
- Convergent boundaries occur where two plates are moving toward each other. Along these boundaries, mountains and trenches are common.
- Transform boundaries occur where two plates are moving past each other. Along these boundaries, earthquakes are common.
- Evidence for plate motion can be seen in various features on Earth. For example, some of the continents have complementary coastlines. This suggests that the continents were once joined together.
Want to join the conversation?
What does asthenosphere mean?(20 votes)
"Asthenosphere" literally translates to "weak sphere", so it makes sense that the asthenosphere is the less rigid part of the mantle. It's right under the lithosphere. The tectonic plates drift on currents in the asthenosphere.
Does that help?(51 votes)
What will Earth look like 200 years from now? Will there be a part of a volcano somewhere, like by a Walmart?(15 votes)
That's a good question.. for your great great great (and so on, I'm not about to calculate how many greats' ) grandkids. As for if there will be a volcano next to a Walmart, I guess that's up to mother nature. ;)(17 votes)
Why do they move and why do they transform into different things.(15 votes)
The tectonic plates move because the heat from radioactive processes within the planet’s interior causes the plates to move, sometimes toward and sometimes away from each other. This movement is called plate motion, or a tectonic shift.(11 votes)
What does asthenosphere mean?(6 votes)
There are different ways to divide the earth into layers. I'm sure you've heard of the crust, mantle, and core. Those layers are differentiated based on chemistry. Said differently, the crust, mantle, and core are distinct because they are made out of different stuff.
We can also divide the earth into layers based on physical and mechanical properties. Those layers are called the lithosphere and asthenosphere. The lithosphere is the outermost layer of earth (including the crust and upper mantle) where the rock is hard, rigid, and brittle. The asthenosphere is below that and is where the rock is hot, ductile, and slowly circulating. Circulating rock in the asthenosphere is the mechanism that drives plate tectonics.(12 votes)
Does America get earthquakes because I have lived here all my life and never felt any vibrations(7 votes)- America does get earthquakes. The most seismically active areas are: the west coast including Alaska, the areas of Tennessee, Kentucky, Illinois, Missouri, and Arkansas near the Mississippi river, the coast of South Carolina, the big island of Hawaii, and the area stretching from Salt Lake City to Yellowstone National Park. The likelihood of other parts of the country producing an earthquake strong enough for you to feel is quite low.(10 votes)
- why are the tectonic plates named?(5 votes)
So we can keep track of them easier(9 votes)
- how likely is it that the ocean will drain?(7 votes)
- The first three-dimensional climate model able to simulate the phenomenon predicts that liquid water will disappear on Earth in approximately one billion years, extending previous estimates by several hundred million years, hope I answered your question.(4 votes)
How Many Tectonic Platers are there in the world(5 votes)- 7 major plates and 8 minor plates so 15 plates in total(7 votes)
- I didn't understend about the tectonc plates on the image(5 votes)
Think of tectonic plates as cookies overlapping, and when they get to their highest breaking point, they become a volcano(5 votes)
- how was all of this discovered?(7 votes)
For both Kyleigh M. and griffinhar30, we found this because we discovered landmasses moved a small amount every year, we tried to dig to the center of the Earth and melted our very best drills, and we used scientific devices to measure things about Earth, thus giving us our best understanding of how this works. (I don't know what devices specifically, since I am not an expert on this)(2 votes)
