Igneous Rocks

Honors Physical Earth Science- Geology Unit

Andesitic Magma

Medium Colored (pink, tan, green, gray), mix of felsic and mafic, composite (strato) volcanoes

Felsic Magma

Light Colored (white, pink, tan, gray), thick and high viscosity, violent eruptions from gas buildup, cinder-cone volcanoes

Mafic Magma

Dark Colored (Gray, Black, Red), thin and low viscosity, shield-cone volcanoes

Coarse Grain

larger than sand, (>2 mm), cools slow, intrusive

Fine Grain

sand sized, (0.5-1.9 mm), cools medium speed, intrusive in thin layers and extrusive in thick layers

Microscopic Grain

smaller than sand, (<0.5 mm), cools fast, extrusive

Phaneritic Texture

Coarse Grain, visible crystals

Aphanitic Texture

Fine Grain, no visible crystals

Porphyritic Texture

Large grains situated in a mass of fine grain. (Phenocrysts are the larger crystals)

Glassy Texture

rapid cooling, shiny and smooth

Pyroclastic Texture

Formed from fire and fragments, ash, tephra, usually vesicular

Pegmatite Texture

Very large crystals bigger than 1 cm, usually found in a granite type rock.