Why is the oldest seafloor less than 180 million years when the oldest continental crust is about 4 billion years old?

It is because of subduction, oceanic crust tends to get colder and denser with age as it spreads from the mid-ocean ridges.

[ answer ]

foliated

[ explanation ]

foliation forms in a rock when pressure squeezes the rock together. the rock then has a design of many different color little lines. there are three types of foliated rock. the types are slate, schist, and gneiss. each type of foliated rock is different based on grain size and foliation characteristics. the lines appear when the rock has been under pressure.

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