4. where is the newest crust? where is the oldest crust? explain why.

Brief Explanations:

The newest crust is found at mid - ocean ridges. Magma rises up at these divergent plate boundaries, cools, and forms new crust. The oldest crust is located far from mid - ocean ridges, typically near subduction zones. As new crust is formed at mid - ocean ridges, the older crust gets pushed away over time and may eventually be subducted back into the mantle at subduction zones.

Answer:

The newest crust is at mid - ocean ridges. The oldest crust is far from mid - ocean ridges, near subduction zones. The reason is that new crust forms at mid - ocean ridges due to magma upwelling and cooling, and older crust is pushed away and can be subducted at subduction zones.