Some of this info is credited to NGT.
4 Players seem to be required.
Stage 1 - Activate the 4 skulls at the quick revive to create an eclipse.
Stage 2 - On either side of the map OUTSIDE there are stepping stones. On the bridge side they are already there, on the opposite side they need to be activated by pressing the button below the statue at the perk machine. One person go on either side and one person stands on a pad, they then step off the pad and tell the player on the opposite side was on it. That player then searches for that symbol, when they find it both players step on the same symbol pads. Repeat for all pads.
Stage 3 - There is a pressure pad in the room that the mine cart takes you too underground. 3 of the players lie on the pressure plate while one person takes the slide down and holds x while looking at the right wall, there is a level that can be pulled but can be tricky to get.
Stage 4 - A crystal will appear at the top of the slide on the top right of the rock face. Use explosives to detach it from the rock then shoot it with the SHRINK RAY, it will shrink then knife it towards the slide, follow it down the slide and then wait for it to go on the blow hole thingy in the corner. Once it is there step on it and the crystal will land on a stand outside.
Stage 5 - There a gas valve that when rotated turns off the gas in the chamber and there are 4 gas leaks along the underground, get a napalm zombie to follow you through each, this sets them alight, then return to the original valve and flip the switch down.
Stage 6 - There is 4 holes in the wall in the tunnel just behind the BIG waterfall, plant a spikemore on the floor facing each hole then switch it to night then get a crawler to go over each claymore, this blocks up the holes then use the button that creates a rush of water.
Stage 7 - There are 12 symbols on the walls around the map these have to all be lit up during Eclipse mode, when this is done look to the grass patch near the mine cart where you cant actually reach and throw an explosive, this sets off a snare trap, when done this activates another crystal.
Stage 8 - There are 4 dials in the mud room, these have to be rotated in to the numbers "16,1,3,4" when done this activates another crystal.
Stage 9 - When you have all the crystals activated, knife the 4 gongs that make a harmonizing tune, then hit the crystal above the mud room with a Pack A Punched Shrink Ray during eclipse mode, this sends a beam towards the meteorite therefore destroying it.
Stage 10 - Approach where the PaP used to be and notice its gone, approach the wall and the people behind it ask you for some dynamite ( THE DYNAMITE CAN BE FOUND ON ONE OF THE CRYSTALS, on the side with the MPL ) , you light up the crystals with the gongs then turn it to night, then the person with a PaP'd Shrink Ray shoots at the crystal with the dynamite attached and another one stand underneath to catch it.