How Old is the Ocean Floor?

In science, we have learned about the continental drift, and are learning about the age of rocks in the ocean and on land. This post is about the age of the ocean floor.

This map I have labeled shows the Mid-Pacific, Mid-Atlantic, and Mid-Indian ridges. At these ridges, new rocks come up from the earth's mantel, and push aside the old rocks. This is why most new rocks are at the ridges, or in the middle of the ocean, and older rocks are closer to land and near continents.

This map shows the Mid-Atlanic ridge, and its youngest and oldest rocks. The youngest rocks in the Atlantic are about 0.5 million years old, and the oldest are about 172 million years old.

Where are the oldest parts of the oceans?

The oldest the parts of the oceans are closer to the continents and land. There are some exceptions, but in general, the closer you get to continents, the older the ocean gets. This happens because the newer rocks come up to the surface in the middle of the ocean, and push the older rocks aside, and put them near the continents.

Do the Pacific, Atlantic, Indian, and Arctic ocean basins have the same age and patterns?

In general, all ocean basins follow the same age pattern (that the younger rocks are in the middle) but an example of an exception would be in the Pacific. There are no old rocks at the western outline of North or South America, while there is a huge outward bulge of really old rocks coming from eastern Asia. In this case, it would just mean that the tectonic plate is at the border of a continent. But in the Atlantic ocean, the tectonic plate is exactly between Africa and North and South America.

How does the age of the ocean floor compare with the age of rocks on the continents?

Rocks on land are 2.5 billion years old on average, while rocks in the ocean are 80 million years old on average. Erosion is one factor that tells us why the ocean rocks are so much younger than rocks on land. Since more erosion happens in the ocean with the water, it eats the rocks away, leaving newer or younger rocks. Another factor could be plate tectonics and ridges. When the new rocks come to the surface of the ocean, and push the older rocks aside, the older ones could either go under the surface, where they are not visible to us, or they could form new land (or connect to land), which would become the old rocks on continents.

These questions were the same as the questions in your pre-test. Reflect on what answers, if any, you changed after completing these activities. What did you learn from these activities with GeoMapApp? Did you need a lot of help from friends or your parents or teacher? What do you think helps you learn new material in science class? 

I think the GeoMapApp helped me understand the age of the ocean really well, because it was a great visual representation. Before I used GeoMap, I think I had a slight idea about what the answers were, but I wasn't sure, and didn't understand them in detail. I know this because the length of my answers has increased, and I was able to explain my answers in better detail. The one question I was way off on was the third one, because I said that rocks in the ocean were older, but my explanation didn't make sense. So the explaining was really where I grew here. Sometimes, the questions confused me, so I learned some things from my parents and teachers. In science class, I like when we get to have an activity like GeoMapApp on our laptops and be able to go at our own pace. But the big downside of using our computers like this is that if we are doing it at home, we can't ask our teacher about any questions. It's better to do it in science class, so we can ask our teacher to explain something to us, or show us something.