Actually, the continents did not form together. They have been joining together and then separating and then joining again continuously for at least the past two billion years. The last time the continents were joined was in the Triassic period, 250 to 200 million years ago (time of Coelophysis, if you are interested in dinosaurs). Before that the continents were separate. The previous supercontinent was the supercontinent of Rodinia, sometime between 800 and 600 million years ago, before the advent of complex multicellular life. There was at least one supercontinent before then, about 1.7 billion years ago, and probably more supercontinents that we know less about. The earliest is speculated to have been around three billion years ago and is nicknamed "Ur".

Large continents have different climates than small continents. We can see this today with the continent of Eurasia, which is the largest of the world's present continents. The interior of Eurasia is dry, has very cold winters, and quite hot summers. This is because water from the oceans creates a moderating effect on climate. It is likely that the interior of Pangaea was a vast desert, and the formation of this desert may have contributed to the Permian-Triassic mass extinction, the largest extinction of all time and the one that made the world ready for the dinosaurs. Rodinia and all of the other supercontinents before it were of course also deserts, deserts more barren than any desert today outside Antarctica, but not because they lacked rainfall, but because plants hadn't evolved yet.

Plate tectonics is what drives the movement of continents. How the continents move causes mountains (if they collide) or oceans (when they move away from each other, water moves in between to create oceans). If the continents didn't move like they did, we would have a very different landscape today. Mountains, valleys and plains that exist today may not have formed. Our continents might be at a different place on the earth, so all the continents could be stuck together at the north pole, or over the equator -- this would mean totally different weather at these locations than we have today, and different ecosystems and animals.

This question is really fun because there is no right answer. We can never know for sure what would happen because we can never test this question in a scientific manner. Because there isn’t a way to really test this, we can speculate all we want about what could have been different if the continents never separated. To begin, I think that trade between civilizations would be very different. For a long time, a majority of trade was done through ships over the ocean, but since the continents were all connected trading via boats would have been much less important. Certain civilizations that relied upon trade to make money, like the Phoenicians, would have been much less powerful. Did you know that Phoenicians invented the alphabet? If they weren’t a powerful nation, maybe we wouldn’t have the idea of an alphabet now.

In a completely different direction, I believe that different cultures would be less diverse than they are currently. Since there wouldn’t be an ocean to separate groups of people, they would have interacted with each other earlier in history and would have mixed their cultures more quickly. This could have been really powerful and perhaps there would be more of a global culture that developed rather than many isolated cultures. As I mentioned earlier, this is pure speculation. You may think differently and that’s totally ok! The main purpose of questions like these is to consider multiple different options and find what you believe is right. Thank you for the interesting question!

I guess there'd be just one big continent, if they never separated. Earth's continents separated, because there are Continental Plates, called Tectonic plates on the earth. The plates are made of rock, and the different plates move back and forth, slowly, causing things like earthquakes and volcanoes.

I was in Iceland last month, and it is on 2 different Tectonic plates, so it has lots of earthquakes and volcanoes. There was a volcano a few years ago that spewed out so much ash that airplane flights were cancelled all over Europe for several days. We visited a place near that volcano in Iceland.

You can read about Plate tectonics in Wikipedia. Some of the planets in our solar system don't have plate tectonics, especially the smaller planets.