This is called Coastal Erosion and it is a combination of wind, tides, waves action on the shoreline. Beach ecosystem is constantly changing due to these circumstances and that is why these regions need special protection. In the US, Pacific coast of North West is a great example of this phenomenon.
Answer: I think the answer is oxygen.
Explanation:
Answer: I think it's B
Explanation: The mantle is the mostly-solid bulk of Earth's interior. So the mantle lies between Earth's dense, super-heated core and its thin outer layer, the crust.