What's the difference between "onto" and "on to" and where should they be used, etc?
"On to" implies that you are removing an object from one place to another, either physically, or conceptually. "Onto" refers to the positioning or placement of something, so that it physically touches the object. To help make this distinction, place a comma in the sentence.
This tells the reader that the speaker plans to travel, until he arrives within close proximity of the rock. The speaker said nothing about making physical contact with the rock. Once the speaker arrives, they may declare,
At this time, the speaker indicates they are about to physically tough the rock, and stand upon it.
The "into" comment is also a matter of action versus position. Also, consider the prepositional context. This statement makes no sense, out of context:
This means the person is going the the inside of something (cave, tunnel, etc.), to the location of the rock. More information about the location of the rock is needed.
Logically, one can not go "into" a rock, which implies the speaker is going to travel to the inside of the rock, for two reasons: first, there is no "inside" of a rock, as it is a solid; and second, the rock is kn fact solid. The concept of going into a rock is nonsense. Well, unless you're abusing hallucinogens.
However, liquids are different. You can logically state,
In these cases, substituting "in to" just doesn't work, because these things are massive and are unable to be contained in a reasonably finite space. Therefore, saying you are "walking in, to the ocean" doesn't make much sense. If anything, you're far more likely to be "walking out, to the ocean." If you were already in the ocean, and the subject were walking toward you, from land, then this could well make sense, but is rarely the case.
The New Oxford American Dictionary has: