The Rock Cycle

The processes through which rocks are formed

Igneous Rocks

Form by the cooling of molten rock (either lava or magma)

Typically have a texture of random crystals

Iceland - 1980s, Alan Rubin

Eruption of Mount St. Helens - May, 1980 (commercial slide)

Mount St. Helens - 2004

Middle and North Sister - Oregon Cascades

Sedimentary Rocks Often form when particles weathered from

earlier rocks are transported (by streams, wind or glaciers) and deposited as sediment

The sediment is then buried and converted to rock by compression and cementation

Typically have a texture of small rounded particles cemented together

French Pete Creek - Oregon Cascades

Basin and Range - eastern Nevada

Cochetopa Creek near Gunnison, Colorado

Creek building delta into Lyman Lake - Washington Cascades

Cape Cod, Massachusetts

Canyonlands National Park, UT - Needles section

Metamorphic Rocks

Generally form when earlier rocks are subjected to high temperatures and/or pressures (BUT without melting!)

Typically have a crystalline texture, with a pattern to the arrangement of crystals

Mt. Jefferson,Oregon Cascades

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