how does the phrase unlike the buried pirates gold in treasure island reflect the tone of the author's conclusion

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

How do convection currents form underwater mountains?

Distance that lewis and clark traveled from st. louis to ft. clatsop near the pacific ocean.