All rock on the ocean floor is less than 180 million years old because _____.the basaltic rock seafloor has been ground away by fine sediment

older rock would have returned to the mantle through subduction

reverse polarity removed older rock strips magnetized in a different direction

the oceans did not exist until more recently than 180 million years ago

Answer:

older rock would have returned to the mantle through subduction

Explanation:

The reason why the ocean floor is only 180 million years old even though the oceans exist much longer then that on Earth, is because of the movement of the tectonic plates, a process through which the oceanic plates are getting subducted and melted into the mantle. The oceans that have existed prior to the ones that exist today haven't really left significant traces of their crust behind them. The reason for this is that the oceanic plates over which these oceans were got below the continental plates, thus got subducted. As they got subducted, they got destroyed in the mantle. The oceanic crust that we have nowadays is only 180 million years old, but as the time passes, the older oceanic crust will face the same destiny, and there will constantly be new one replacing it.

Final answer:

All rock on the ocean floor is less than 180 million years old due to the process of subduction. When oceanic plates collide, the denser one is forced beneath into the mantle, where it's recycled into new rock. Thus, the seafloor never gets too old as it's frequently replenished.

Explanation:

All rock on the ocean floor is less than 180 million years old because older rock would have returned to the mantle through subduction. When discussing the age of the ocean floor, it's crucial to consider the process of plate tectonics, specifically subduction zones. The Earth's lithosphere is divided into several large and small pieces known as tectonic plates. These plates are in constant motion, and when an oceanic plate collides with another oceanic or continental plate, the denser one is forced under the less dense one. This process is known as subduction. As the plate is forced into the mantle, it melts and is recycled into new rock. This ensures that the seafloor does not get too old because it's continually being replenished with new rock pushed up from spreading centers, where new oceanic crust is created.

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