Chunked LOD
Pre-builds terrain as a quadtree of static chunks and draws the coarsest chunk whose screen error is small enough — made for the GPU's big static buffers.
Thatcher Ulrich described the method in a 2002 SIGGRAPH course. Each node in a quadtree is a finished, static mesh over its patch of the world at some resolution; the root covers everything coarsely, the leaves cover small tiles finely. To render, you walk down the tree and stop as soon as a node's expected pixel error drops below a threshold — that chunk gets drawn.
Because the chunks are static they can sit in GPU buffers and be streamed from disk, which makes planet-sized datasets tractable — the basis of Google Earth-style terrain. Seams between neighbors on different levels are hidden with skirts or by morphing vertices smoothly between levels.