200 million years ago: Pacific and North American tectonic plates meet; Pacific plate slides under North American plate; deep below earth’s surface, Pacific plate melts into magma.
100 to 80 million years ago: Magma rises and cools below surface, forming huge blocks of granite.
50 million years ago: Surface of rolling hills and streams emerges, including tranquil Merced River.
10 million years ago: Sierra Nevada range rises, tilting toward the west. Merced flows more rapidly, carving valley.
3 million years ago: Canyon now 3,000 feet deep as ice age approaches.
1 million years ago to 250,000 years ago: glaciers carve valley into “U” shape, creating hanging valleys, waterfalls.
30,000 years ago: More glacier movement at slower pace.
10,000 years ago: glaciers melt, becoming a lake; sediment fills lake, forming valley floor as it exists now.
Today: sedimentation process continues; Mirror Lake filling in.
