Play Glacial Chasm either from your hand or from your graveyard.
When Glacial Chasm enters the battlefield, its second ability triggers, causing you to sacrifice another land you control.
Play any land from your graveyard.
At the beginning of your next upkeep, Glacial Chasm's cumulative upkeep ability triggers, allowing you to choose not to pay the cost and sacrifice it instead.
Repeat.

Prevent all damage that would be dealt to you

Glacial Chasm

Exploration

Ramunap Excavator

Cast Walk the Aeons by paying {4}{U}{U}, sacrificing Mystic Sanctuary and two other Islands, causing you to take an extra turn after this one and returning Walk the Aeons to your hand.
Play any Island except Mystic Sanctuary from your graveyard.
Move to your next turn.
Cast Walk the Aeons by paying {4}{U}{U}, causing you to take an extra turn after this one.
Play any Island except Mystic Sanctuary from your graveyard, then play Mystic Sanctuary from your graveyard.
When Mystic Sanctuary enters the battlefield, it triggers, putting Walk the Aeons on top of your library from your graveyard.
Move to your next turn, drawing Walk the Aeons during your draw step.
Repeat.

Combos with "Exploration"