They look different because when a rock is at the beginning of a river they havent barely started their journey yet so they're probably a lot bigger and not so crucked as to when they are at the bottom after they have fallen got scratched and had bits chipped off of them ...
That would be the Indus River.
A river would be the Ganges.
Because the river attached to the Sea and then all the rocks or the seashells would go with the river. Tip: river is like a stream.It moves.
River Rocks would be made out of whatever type of rocks are around the river. Although, I would assume not all types of rocks tend to grind into round balls.Granite is very tough, and is a very common type of river rock.
rocks?
Sedimentary, Igneous, and/or Metamorphic
sedimentary
First of all, why would rocks move in different directions? Even though rocks could move in different directions, it is not possible for them to move on their own. Rocks have to have force applied to them in order to move.
a river
ever since people would start throwing away stuff, like in the beginning of the 1900s.
Depending on the minerals in their composition, some rocks are harder than others. Rocks that contain minerals with higher ratings on the Mohs scale are harder, and would erode more slowly than other rocks.
as every river is different, it would depend on which river and the draught of that river or the amount of water displaced by a boat on that river