nearly one third of the united states is covered by the mississippi river choose... .; a lake can form when a river is blocked by mud and lava from a geyser.; lakes can disappear due to; a stream that flows into two different rivers is part of two; though it occurs naturally, human activities can increase; a river and all the streams and smaller rivers that flow into it together make up a; compared to lakes, ponds are usually; though it occurs naturally in lakes, human activities can increase ___.