You can create an infinite well using two buckets of water and a hole that is one block deep and two blocks by two blocks wide. I’m wondering if it’s possible to do a similar thing with lava, now that obsidian is so valuable for making portals. I have an idea for making it easier for creating portals, but it’s dependent on having an effectively infinite source of lava very close to where I want to create the portal. So is this possible? If so, how?
Note: This answer exploits an old bug which has been patched in the current version of Minecraft.
No, lava can’t replicate, but you can create unlimited obsidian from one lava block using a glitch involving lava flow onto redstone wire: