This is a bit of a two part question on the cosmic event.
We know that people, ponies and dragons have made the shift [Dead or Alive] between worlds.
But what of other things like trees or houses? Bigger still, whole terrain changes like lakes, rivers or even a mountain?
Ok I admit that the idea of something like a mountain suddenly appearing in a location is weird but I do see the event setting off volcanoes and earthquakes in a chain reaction.

The other part of my question involves the citizens of Equestria. They were prepared for the event.
So what sort of education/training did they receive, if any. From what I understand, Twilight Sparkle had ascended to an alicorn about 6 years ago. In that time what events have occurred and what are the ages of some of the known characters from Equestria.
An example would be the CMC: did they get there cutie marks or are they still in school? Equestrians have magic but what is their understanding and level of technology? Is their technology magic or non-magic based?

To quote Richard Rogers
The only way forward, if we are going to improve the quality of the environment, is to get everybody involved.

4171292 I actually thought about that too, In fact, one idea I have that some creature from the pony planet (I'll just call it Equis) to earth will change not just in appearance, but in nature as well. An Example is the Windigo become Wendigos and instead of feeding on hate, they feed on anything and they look like Mutated versions of the speices they once were and anyone in a cold environment that practices cannibalism become Wendigos losing all their sapient thought reduce to mere beasts.

I have to agree with you. The idea that the crossing between Equis and Earth being perfect all the time isn't the right idea. I image seeing cases where you find not only some poor soul half phased in a wall or rock but only a piece of them showing up. Beware the hand of Discord!

This brings up the concept of 2 creatures being merged. An example would be Headbanger from cartoon series Toxic Crusaders where the left head, arm and leg are what's left of the surf Fender and the right head, arm and leg belong to the mad scientist Dr. Bender. Literally smashing 2 things together.

The other possibility is that of a cross fusion of two creatures like the movie The Fly for example. Picture a humans slow decent into possible madness as said human becomes a Human/Windigo hybrid.

I see a lot of get out of Tartarus free cards getting handed out.

4172202 I also Entertain the Idea of Humans gaining magic. My idea is that Earth always had magic and humans could preformed it, but at some point and for some reason (My idea is that the Catholic Church along with other the Abrahamnic Religions put an end to it), Earth and it's inhabitants became deafened it to. Also my idea of human magic is not spell weaving, but Theurgy (means divine working where we call upon gods, spirits, ect. through incantations, rituals, prayer). Funfact: Voodoo actually has roots in Catholicism. However, not every human can do magic.

Also I said that creature changing entirely, not merging. Based on some of our own folklore.

4171292 No landmasses have changed as a result of the merge -- all new additions are biological living things. Before you ask, this does not include the Tartarus prison, which is actually a separate dimension that was intentionally locked away from accessible time and space.

Ages are as follows:

CMC and other known young pony characters -- young teens/early puberty (to be chosen as desired, as the exact ages aren't relevant)

The Element-Bearers: early twenties (other than the obvious, such as Fluttershy being a year older than Pinkie, the exact ages aren't important)

Spike: Same age as the young ponies

Cadence and Shining Armor: early thirties

The training received to prepare the people of Equestria and their world was physical and magical training meant to bring their strength and inner magical potential to its maximum possible level, respectively. As anyone who has entered into -- and stuck with -- a strict physical training regimen can attest, a year alone can change everything about physical appearance. Beyond that, all Equestrians -- and, presumably, the other races -- were given basic to advanced (depending on the individual) self-defense training, as well as basic survival tactics, the latter of which is only so useful because of the difference between worlds.

Pony technology is comparable to twenty-first century man, minus space travel and firearms. Refineries that gather ambient magic transform it into raw energy for use in their devices; because of this, there is little to no fossil fuel burning across the planet. Plumbing, however, is much the same.

The CMC have received their cutie marks, but because I won't be writing about them directly, I'll leave that up to the fandom as to what they'll be.