These three african nations all have coastlines on the red sea

The coastline of the red sea that are African nations are Egypt Sudan and Eritrea. A red sea is the saltiest sea in the world and it is connected to the ocean without passing any river. The term "red" is due to the cyanobacteria that composes in that sea which is in color red.

The answer to the question is moraine

Answer they are produced by collision of tectonic plates;