The correct answer to the first question regarding how continental crust differs from oceanic crust is:
Oceanic crust is thinner and younger.
Explanation:
- Density: Oceanic crust is generally denser than continental crust. It is primarily composed of basalt, while continental crust is primarily composed of granite, which is less dense.
- Thickness: Oceanic crust is thinner, generally about 5-10 kilometers thick, compared to the continental crust, which can be up to 70 kilometers thick or more.
- Age: Oceanic crust is typically younger than continental crust because it is continuously being generated at mid-ocean ridges and recycled back into the mantle at subduction zones. In contrast, continental crust can be billions of years old.
For the second part of your message regarding tectonic plate movements:
Each of these statements describes different geological processes that occur due to the movement of tectonic plates:
- The seafloor is spreading. - This refers to the process at mid-ocean ridges where new oceanic crust is formed as magma rises to the surface.
- An oceanic plate is subducting. - This occurs when an oceanic plate converges with another plate and is forced down into the mantle.
- Two continental plates are colliding. - This can create mountain ranges and is characteristic of continental-continental convergence.
- Two plates are sliding past each other. - This describes a transform boundary, where plates move horizontally against each other.
If you need explanations for these plate movements or if you have more questions, feel free to ask!