The idea of this deck is to destroy your opponent's sites while overwhelming the realm with your own sites. Ideally, your opponent will be resource starved and vulnerable to attacks from big minions that you were able to bring into play faster than expected.

Some notes:

It's possible to play 3 sites in one turn using the Geomancer's basic ability, Frontier Settlers, and Landmass. You shouldn't have to draw a site ever (aside from your opening hand).
Between Tithe, Landmass, Land Surveyors, and Frontier Settlers, you can draw 12 sites, and put 6 directly into play; giving you some control over site placement.
Hitting Star-Seeds of Uhr (or Dream Quest) in your opening hand or on your first draw basically guarantees realm expansion and will allow you simply draw spells for the rest of the game.
Roots of Yggdrasil and Scorched Earth act as reset buttons. Bedrock cannot be destroyed, so you if you do hit the "History Eraser buttons", you'll at least have Bedrock as a mana source.
Queen of Midland helps assure that you always have at least as many cards as your opponent, while Dhol Chants can provide a mid/late game "mass tutor" to change the game (ideally you would tap down Land Surveyors and Frontier Settlers).
Merlin is your Omphalos engine.
Lord of Destruction is your main site destruction engine.
Nadir seed isn't a necessary inclusion and can be swapped with Whirling Blades. However, Ophanim can deposit a Nadir Seed to an enemy site, Earthquake (or Cave-In, in the collection) can burrow the relic, making it harder to remove.
Waypoint portal, Recall, and Blink provide forced movement, in case your Geomancer gets a little stuck.
Divine Healing will hopefully offset aggro damage. Angel's Egg will nullify Ring of Morrigan.
Silver Bullets provide access to a variety of situational solutions, I recommend adding projectile spells in the remaining 2 slots.
Squirming Mass can be a cheap bruiser, but it is best to cast him alongside The Black Plague, Raze, Scorched Earth, or keep him nearby Lord of Destruction.

Vulnerabilities:

Submerge and flooding. In general, there are few defenses against these - swapping in creatures that can Submerge is the obvious answer.
Aggro exposure. With a ton of sites in play, there are a ton of targets. Mount Ussar Sanctuary and Dome of Osiros will help, but Geomancer will be out roaming the realm for a not insignificant portion of the game, so projectiles and aggro decks will have a field day. Most of your mana dorks are vulnerable to aggro damage as well.
Honestly, bad draws and stagnation happen. Replacing Talamh Dreig and Conqueror Worm with lower cost minions could help, but even then, bad draws happen. Blink, Highland Princess, Queen of Midland, and Dhol Chants should alleviate or correct bad draws, but they require some kind of reasonable boardstate to start with. Getting stalled on turn 3 or 4 is possible.

Geophobia

@mehfistopheles