Creating a volcano out of nothing sounds like a plan concocted by Doctor Doom. But there is at least one way we could try to create a volcano in real life, too.
Most volcanoes are created when tectonic plates – the pieces of Earth's crust and mantle on which we live – collide or separate. These movements often create extremely volatile chains of volcanoes such as those in the Pacific Ring of Fire. But moving tectonic plates with human (or superhuman) effort sounds like an extremely difficult avenue for creating a controllable volcano (although it could work for a devious Doctor Doom looking to create a volcanic moat around New Latveria), so let's scrap that possibility.
Another type of volcano is on a "rift," or a place where the planet's crust has worn thin. A great example of a rift is the Rio Grande Rift, a chain of volcanoes extending from the middle of Colorado to Chihuahua, Mexico. If someone out there is setting out to create an artificial volcano, this would likely be the easiest type to create. Removing additional dirt and rock at a place where the Earth's crust is extremely thin could, theoretically, allow for an outpouring of lava and create a volcano.
Hitting a magma pocket while boring through the crust is the key, but a supervillain would want to make a radiant display. The thickness of the planet's crust varies greatly — it is often thinner along the ocean bed and thicker in in the middle of a continent. Digging with the hopes of hitting a pocket of molten rock at any point is a dangerous operation, though. Hopefully the villain has plenty of disposable henchmen and henchwomen.
Extremely Deep Holes
Exxon's Sakhalin-I Odoptu OP-11 well currently holds the record for deepest artificial hole on the planet, coming in at 12,345 meters.
Russia's Kola Superdeep Borehole is the product of a nineteen year long scientific expedition. Kola extends a little more than 12 kilometers deep through an estimated 30+ kilometers of crust under the Balkans.
The borehole currently gives the best chance at penetrating the crust of a large landmass for enterprising super villains, but they would still have a long way to go. A nuclear payload combined with a phenomenally deep starter borehole could create enough damage to bring forth molten rock. Cut to images of squirly miners from Armageddon, sent on an adventure to drill into and nuke the crust.
Once past the crust, a much thicker layer, the mantle, is present. Estimated at two-thousand plus kilometers, boring through the mantle would be an altogether impractical task (sorry fans of the Total Recall remake) for a man or superman.
Molten rock exists in both the crust and the mantle, so, at least theoretically, magma could be found at almost any point while boring a hole through the Earth. Although magma could be hit anywhere along the way, it is hard to know what will happen when that pocket of red gold is poked.
What Would an Artificial Volcano Look Like?
Due to the lack of disturbance at the borders of tectonic plates, a borehole created in the middle of a plate would lack the mountainous formations seen in magnificent volcanoes like Mount St. Helens or Mauna Loa.
The molten rock would need to be under extreme pressure to shoot back up to the surface. An artificial volcano, if created in this way, would simply look like a deep hole in the ground for decades until the forces of nature took over.
Creating a volcano might be possible, but the event would be underwhelming and require an enormous amount of people power. An up-and-coming super villain would have better luck threatening to initiate an eruption at an already existing volcano, making use of any nuclear weapons he or she might have lying around.
Top image is from the Marvel Comic book Doctor Doom and the Masters of Evil #4. Image of the Kilauea Volcano via Image Editor/Flickr, while the image of the Kola Superdeep Borehole via Andre Belozeroff/CC. Sources linked within the article.