What man-made lake was created by the building of the hoover dam?

The difference(s) between the grand canyon and valles marineris is/are: (a) the grand canyon was formed by water, but valles marineris was not. (a) valles marineris is much longer than the grand canyon. (c) valles marineris is much wider than the grand canyon. (d) valles marineris has large volcanoes near it. all of the above

Where is the vascular system located

This is a 2017 topographic map of puerto rico in the united states, and i'm sorry that people there have suffered such a disaster. i want to ask, what do the yellow dots and areas represent on this graph? and the blue area and the little blue circle, and the little blue sign that looks like a signal tower, what do they stand for?