Main content
Course: Middle school Earth and space science - NGSS > Unit 4
Lesson 3: Plate tectonicsPlate tectonics and the ocean floor
Review your understanding of plate tectonics and the ocean floor in this free article aligned to NGSS standards.
Key points:
- There are two types of tectonic plates: oceanic and continental. Oceanic plates make up the ocean floor. Continental plates make up the continents.
- Both oceanic and continental plates are topped by crust. On average, oceanic crust is denser than continental crust.
- A trench forms when an oceanic plate collides with another plate at a convergent boundary. When this happens, the denser plate is subducted, or pushed under, the less dense plate.
- A mid-ocean ridge forms when two oceanic plates move apart at a divergent boundary.
- New oceanic crust is created at mid-ocean ridges. As it ages, it moves away from the ridge and becomes cooler and denser. Eventually, the crust reaches a trench and is destroyed.
Want to join the conversation?
why do waves in the ocean happen(9 votes)
The regular waves that you see in the ocean are caused by wind. Storm surges, underwater earthquakes, and underwater landslides also generate waves, but those are relatively rare events.(17 votes)
- do fossils stay fossils or just turn into dust or rocks?(12 votes)
To add to haziekat4's answer, if it happens in a jungle, it won't become a fossil at all. If they are in a really inactive location, they will last a long time, and if they are in an active location, they will get destroyed quickly. But yes, over time fossils will crumble into dust. Also, as for turning into a rock, they already did that.(1 vote)
- what cause waves in the ocean(7 votes)
- This is the first good question I have seen, so thank you. (I up voted this) Waves are most commonly caused by wind but can be caused by landslides, volcanic eruptions, earthquakes, and more.(2 votes)
Will the people go and look in the trench for other animals that haven't been seen before.(5 votes)
yes they will so we don't face them in the near future(5 votes)
can people go in a trench, find megalodon DNA, and bring it back?(5 votes)
1. how does the black hole is form.
2. I am the biggest bird.(3 votes)- A black hole can form by a star 10-20 times more mass than our sun collapses on it self.(3 votes)
In 5,000000000 years, the sun will explode and Earth will die.(3 votes)
Actually, I'm pretty sure the same amount of years but the Earth would renew and life will stay. I know this isn't a question but I'm just stating what I think would happen.(2 votes)
- what would happen if the world would run out of water(3 votes)
Without water, the Earth would become a barren and inhospitable place. All plants and animals would die, and the planet's ecosystems would collapse. The loss of water would also have a profound impact on the Earth's climate and weather patterns.(1 vote)
dont hate my question is the tectonic plate moving now(3 votes)
It's a good question! Yes, it is, but so slowly that we probably wouldn't notice for a few centuries (or even millenia) or so.(1 vote)
- why do the waves in the ocean happen?(2 votes)
- It is because of the moon and it's gravity(2 votes)
